redis / src / sentinel.c

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
/* Redis Sentinel implementation
 *
 * Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *   * Neither the name of Redis nor the names of its contributors may be used
 *     to endorse or promote products derived from this software without
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "redis.h"
#include "hiredis.h"
#include "async.h"

#include <ctype.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/wait.h>

extern char **environ;

#define REDIS_SENTINEL_PORT 26379

/* ======================== Sentinel global state =========================== */

typedef long long mstime_t; /* millisecond time type. */

/* Address object, used to describe an ip:port pair. */
typedef struct sentinelAddr {
    char *ip;
    int port;
} sentinelAddr;

/* A Sentinel Redis Instance object is monitoring. */
#define SRI_MASTER  (1<<0)
#define SRI_SLAVE   (1<<1)
#define SRI_SENTINEL (1<<2)
#define SRI_DISCONNECTED (1<<3)
#define SRI_S_DOWN (1<<4)   /* Subjectively down (no quorum). */
#define SRI_O_DOWN (1<<5)   /* Objectively down (quorum reached). */
#define SRI_MASTER_DOWN (1<<6) /* A Sentinel with this flag set thinks that
                                   its master is down. */
/* SRI_CAN_FAILOVER when set in an SRI_MASTER instance means that we are
 * allowed to perform the failover for this master.
 * When set in a SRI_SENTINEL instance means that sentinel is allowed to
 * perform the failover on its master. */
#define SRI_CAN_FAILOVER (1<<7)
#define SRI_FAILOVER_IN_PROGRESS (1<<8) /* Failover is in progress for
                                           this master. */
#define SRI_I_AM_THE_LEADER (1<<9)     /* We are the leader for this master. */
#define SRI_PROMOTED (1<<10)            /* Slave selected for promotion. */
#define SRI_RECONF_SENT (1<<11)     /* SLAVEOF <newmaster> sent. */
#define SRI_RECONF_INPROG (1<<12)   /* Slave synchronization in progress. */
#define SRI_RECONF_DONE (1<<13)     /* Slave synchronized with new master. */
#define SRI_FORCE_FAILOVER (1<<14)  /* Force failover with master up. */
#define SRI_SCRIPT_KILL_SENT (1<<15) /* SCRIPT KILL already sent on -BUSY */

#define SENTINEL_INFO_PERIOD 10000
#define SENTINEL_PING_PERIOD 1000
#define SENTINEL_ASK_PERIOD 1000
#define SENTINEL_PUBLISH_PERIOD 5000
#define SENTINEL_DOWN_AFTER_PERIOD 30000
#define SENTINEL_HELLO_CHANNEL "__sentinel__:hello"
#define SENTINEL_TILT_TRIGGER 2000
#define SENTINEL_TILT_PERIOD (SENTINEL_PING_PERIOD*30)
#define SENTINEL_DEFAULT_SLAVE_PRIORITY 100
#define SENTINEL_PROMOTION_RETRY_PERIOD 30000
#define SENTINEL_SLAVE_RECONF_RETRY_PERIOD 10000
#define SENTINEL_DEFAULT_PARALLEL_SYNCS 1
#define SENTINEL_MIN_LINK_RECONNECT_PERIOD 15000
#define SENTINEL_DEFAULT_FAILOVER_TIMEOUT (60*15*1000)
#define SENTINEL_MAX_PENDING_COMMANDS 100
#define SENTINEL_EXTENDED_SDOWN_MULTIPLIER 10

/* How many milliseconds is an information valid? This applies for instance
 * to the reply to SENTINEL IS-MASTER-DOWN-BY-ADDR replies. */
#define SENTINEL_INFO_VALIDITY_TIME 5000
#define SENTINEL_FAILOVER_FIXED_DELAY 5000
#define SENTINEL_FAILOVER_MAX_RANDOM_DELAY 10000

/* Failover machine different states. */
#define SENTINEL_FAILOVER_STATE_NONE 0  /* No failover in progress. */
#define SENTINEL_FAILOVER_STATE_WAIT_START 1  /* Wait for failover_start_time*/ 
#define SENTINEL_FAILOVER_STATE_SELECT_SLAVE 2 /* Select slave to promote */
#define SENTINEL_FAILOVER_STATE_SEND_SLAVEOF_NOONE 3 /* Slave -> Master */
#define SENTINEL_FAILOVER_STATE_WAIT_PROMOTION 4 /* Wait slave to change role */
#define SENTINEL_FAILOVER_STATE_RECONF_SLAVES 5 /* SLAVEOF newmaster */
#define SENTINEL_FAILOVER_STATE_WAIT_NEXT_SLAVE 6 /* wait replication */
#define SENTINEL_FAILOVER_STATE_ALERT_CLIENTS 7 /* Run user script. */
#define SENTINEL_FAILOVER_STATE_WAIT_ALERT_SCRIPT 8 /* Wait script exec. */
#define SENTINEL_FAILOVER_STATE_DETECT_END 9 /* Check for failover end. */
#define SENTINEL_FAILOVER_STATE_UPDATE_CONFIG 10 /* Monitor promoted slave. */

#define SENTINEL_MASTER_LINK_STATUS_UP 0
#define SENTINEL_MASTER_LINK_STATUS_DOWN 1

/* Generic flags that can be used with different functions. */
#define SENTINEL_NO_FLAGS 0
#define SENTINEL_GENERATE_EVENT 1
#define SENTINEL_LEADER 2
#define SENTINEL_OBSERVER 4

/* Script execution flags and limits. */
#define SENTINEL_SCRIPT_NONE 0
#define SENTINEL_SCRIPT_RUNNING 1
#define SENTINEL_SCRIPT_MAX_QUEUE 256
#define SENTINEL_SCRIPT_MAX_RUNNING 16
#define SENTINEL_SCRIPT_MAX_RUNTIME 60000 /* 60 seconds max exec time. */
#define SENTINEL_SCRIPT_MAX_RETRY 10
#define SENTINEL_SCRIPT_RETRY_DELAY 30000 /* 30 seconds between retries. */

typedef struct sentinelRedisInstance {
    int flags;      /* See SRI_... defines */
    char *name;     /* Master name from the point of view of this sentinel. */
    char *runid;    /* run ID of this instance. */
    sentinelAddr *addr; /* Master host. */
    redisAsyncContext *cc; /* Hiredis context for commands. */
    redisAsyncContext *pc; /* Hiredis context for Pub / Sub. */
    int pending_commands;   /* Number of commands sent waiting for a reply. */
    mstime_t cc_conn_time; /* cc connection time. */
    mstime_t pc_conn_time; /* pc connection time. */
    mstime_t pc_last_activity; /* Last time we received any message. */
    mstime_t last_avail_time; /* Last time the instance replied to ping with
                                 a reply we consider valid. */
    mstime_t last_pong_time;  /* Last time the instance replied to ping,
                                 whatever the reply was. That's used to check
                                 if the link is idle and must be reconnected. */
    mstime_t last_pub_time;   /* Last time we sent hello via Pub/Sub. */
    mstime_t last_hello_time; /* Only used if SRI_SENTINEL is set. Last time
                                 we received an hello from this Sentinel
                                 via Pub/Sub. */
    mstime_t last_master_down_reply_time; /* Time of last reply to
                                             SENTINEL is-master-down command. */
    mstime_t s_down_since_time; /* Subjectively down since time. */
    mstime_t o_down_since_time; /* Objectively down since time. */
    mstime_t down_after_period; /* Consider it down after that period. */
    mstime_t info_refresh;  /* Time at which we received INFO output from it. */

    /* Master specific. */
    dict *sentinels;    /* Other sentinels monitoring the same master. */
    dict *slaves;       /* Slaves for this master instance. */
    int quorum;         /* Number of sentinels that need to agree on failure. */
    int parallel_syncs; /* How many slaves to reconfigure at same time. */
    char *auth_pass;    /* Password to use for AUTH against master & slaves. */

    /* Slave specific. */
    mstime_t master_link_down_time; /* Slave replication link down time. */
    int slave_priority; /* Slave priority according to its INFO output. */
    mstime_t slave_reconf_sent_time; /* Time at which we sent SLAVE OF <new> */
    struct sentinelRedisInstance *master; /* Master instance if SRI_SLAVE is set. */
    char *slave_master_host;    /* Master host as reported by INFO */
    int slave_master_port;      /* Master port as reported by INFO */
    int slave_master_link_status; /* Master link status as reported by INFO */
    /* Failover */
    char *leader;       /* If this is a master instance, this is the runid of
                           the Sentinel that should perform the failover. If
                           this is a Sentinel, this is the runid of the Sentinel
                           that this other Sentinel is voting as leader.
                           This field is valid only if SRI_MASTER_DOWN is
                           set on the Sentinel instance. */
    int failover_state; /* See SENTINEL_FAILOVER_STATE_* defines. */
    mstime_t failover_state_change_time;
    mstime_t failover_start_time;   /* When to start to failover if leader. */
    mstime_t failover_timeout;      /* Max time to refresh failover state. */
    struct sentinelRedisInstance *promoted_slave; /* Promoted slave instance. */
    /* Scripts executed to notify admin or reconfigure clients: when they
     * are set to NULL no script is executed. */
    char *notification_script;
    char *client_reconfig_script;
} sentinelRedisInstance;

/* Main state. */
struct sentinelState {
    dict *masters;      /* Dictionary of master sentinelRedisInstances.
                           Key is the instance name, value is the
                           sentinelRedisInstance structure pointer. */
    int tilt;           /* Are we in TILT mode? */
    int running_scripts;    /* Number of scripts in execution right now. */
    mstime_t tilt_start_time;   /* When TITL started. */
    mstime_t previous_time;     /* Time last time we ran the time handler. */
    list *scripts_queue;    /* Queue of user scripts to execute. */
} sentinel;

/* A script execution job. */
typedef struct sentinelScriptJob {
    int flags;              /* Script job flags: SENTINEL_SCRIPT_* */
    int retry_num;          /* Number of times we tried to execute it. */
    char **argv;            /* Arguments to call the script. */
    mstime_t start_time;    /* Script execution time if the script is running,
                               otherwise 0 if we are allowed to retry the
                               execution at any time. If the script is not
                               running and it's not 0, it means: do not run
                               before the specified time. */
    pid_t pid;              /* Script execution pid. */
} sentinelScriptJob;

/* ======================= hiredis ae.c adapters =============================
 * Note: this implementation is taken from hiredis/adapters/ae.h, however
 * we have our modified copy for Sentinel in order to use our allocator
 * and to have full control over how the adapter works. */

typedef struct redisAeEvents {
    redisAsyncContext *context;
    aeEventLoop *loop;
    int fd;
    int reading, writing;
} redisAeEvents;

static void redisAeReadEvent(aeEventLoop *el, int fd, void *privdata, int mask) {
    ((void)el); ((void)fd); ((void)mask);

    redisAeEvents *e = (redisAeEvents*)privdata;
    redisAsyncHandleRead(e->context);
}

static void redisAeWriteEvent(aeEventLoop *el, int fd, void *privdata, int mask) {
    ((void)el); ((void)fd); ((void)mask);

    redisAeEvents *e = (redisAeEvents*)privdata;
    redisAsyncHandleWrite(e->context);
}

static void redisAeAddRead(void *privdata) {
    redisAeEvents *e = (redisAeEvents*)privdata;
    aeEventLoop *loop = e->loop;
    if (!e->reading) {
        e->reading = 1;
        aeCreateFileEvent(loop,e->fd,AE_READABLE,redisAeReadEvent,e);
    }
}

static void redisAeDelRead(void *privdata) {
    redisAeEvents *e = (redisAeEvents*)privdata;
    aeEventLoop *loop = e->loop;
    if (e->reading) {
        e->reading = 0;
        aeDeleteFileEvent(loop,e->fd,AE_READABLE);
    }
}

static void redisAeAddWrite(void *privdata) {
    redisAeEvents *e = (redisAeEvents*)privdata;
    aeEventLoop *loop = e->loop;
    if (!e->writing) {
        e->writing = 1;
        aeCreateFileEvent(loop,e->fd,AE_WRITABLE,redisAeWriteEvent,e);
    }
}

static void redisAeDelWrite(void *privdata) {
    redisAeEvents *e = (redisAeEvents*)privdata;
    aeEventLoop *loop = e->loop;
    if (e->writing) {
        e->writing = 0;
        aeDeleteFileEvent(loop,e->fd,AE_WRITABLE);
    }
}

static void redisAeCleanup(void *privdata) {
    redisAeEvents *e = (redisAeEvents*)privdata;
    redisAeDelRead(privdata);
    redisAeDelWrite(privdata);
    zfree(e);
}

static int redisAeAttach(aeEventLoop *loop, redisAsyncContext *ac) {
    redisContext *c = &(ac->c);
    redisAeEvents *e;

    /* Nothing should be attached when something is already attached */
    if (ac->ev.data != NULL)
        return REDIS_ERR;

    /* Create container for context and r/w events */
    e = (redisAeEvents*)zmalloc(sizeof(*e));
    e->context = ac;
    e->loop = loop;
    e->fd = c->fd;
    e->reading = e->writing = 0;

    /* Register functions to start/stop listening for events */
    ac->ev.addRead = redisAeAddRead;
    ac->ev.delRead = redisAeDelRead;
    ac->ev.addWrite = redisAeAddWrite;
    ac->ev.delWrite = redisAeDelWrite;
    ac->ev.cleanup = redisAeCleanup;
    ac->ev.data = e;

    return REDIS_OK;
}

/* ============================= Prototypes ================================= */

void sentinelLinkEstablishedCallback(const redisAsyncContext *c, int status);
void sentinelDisconnectCallback(const redisAsyncContext *c, int status);
void sentinelReceiveHelloMessages(redisAsyncContext *c, void *reply, void *privdata);
sentinelRedisInstance *sentinelGetMasterByName(char *name);
char *sentinelGetSubjectiveLeader(sentinelRedisInstance *master);
char *sentinelGetObjectiveLeader(sentinelRedisInstance *master);
int yesnotoi(char *s);
void sentinelDisconnectInstanceFromContext(const redisAsyncContext *c);
void sentinelKillLink(sentinelRedisInstance *ri, redisAsyncContext *c);
const char *sentinelRedisInstanceTypeStr(sentinelRedisInstance *ri);
void sentinelAbortFailover(sentinelRedisInstance *ri);
void sentinelEvent(int level, char *type, sentinelRedisInstance *ri, const char *fmt, ...);
sentinelRedisInstance *sentinelSelectSlave(sentinelRedisInstance *master);
void sentinelScheduleScriptExecution(char *path, ...);
void sentinelStartFailover(sentinelRedisInstance *master, int state);
void sentinelDiscardReplyCallback(redisAsyncContext *c, void *reply, void *privdata);

/* ========================= Dictionary types =============================== */

unsigned int dictSdsHash(const void *key);
int dictSdsKeyCompare(void *privdata, const void *key1, const void *key2);
void releaseSentinelRedisInstance(sentinelRedisInstance *ri);

void dictInstancesValDestructor (void *privdata, void *obj) {
    releaseSentinelRedisInstance(obj);
}

/* Instance name (sds) -> instance (sentinelRedisInstance pointer)
 *
 * also used for: sentinelRedisInstance->sentinels dictionary that maps
 * sentinels ip:port to last seen time in Pub/Sub hello message. */
dictType instancesDictType = {
    dictSdsHash,               /* hash function */
    NULL,                      /* key dup */
    NULL,                      /* val dup */
    dictSdsKeyCompare,         /* key compare */
    NULL,                      /* key destructor */
    dictInstancesValDestructor /* val destructor */
};

/* Instance runid (sds) -> votes (long casted to void*)
 *
 * This is useful into sentinelGetObjectiveLeader() function in order to
 * count the votes and understand who is the leader. */
dictType leaderVotesDictType = {
    dictSdsHash,               /* hash function */
    NULL,                      /* key dup */
    NULL,                      /* val dup */
    dictSdsKeyCompare,         /* key compare */
    NULL,                      /* key destructor */
    NULL                       /* val destructor */
};

/* =========================== Initialization =============================== */

void sentinelCommand(redisClient *c);
void sentinelInfoCommand(redisClient *c);

struct redisCommand sentinelcmds[] = {
    {"ping",pingCommand,1,"",0,NULL,0,0,0,0,0},
    {"sentinel",sentinelCommand,-2,"",0,NULL,0,0,0,0,0},
    {"subscribe",subscribeCommand,-2,"",0,NULL,0,0,0,0,0},
    {"unsubscribe",unsubscribeCommand,-1,"",0,NULL,0,0,0,0,0},
    {"psubscribe",psubscribeCommand,-2,"",0,NULL,0,0,0,0,0},
    {"punsubscribe",punsubscribeCommand,-1,"",0,NULL,0,0,0,0,0},
    {"info",sentinelInfoCommand,-1,"",0,NULL,0,0,0,0,0}
};

/* This function overwrites a few normal Redis config default with Sentinel
 * specific defaults. */
void initSentinelConfig(void) {
    server.port = REDIS_SENTINEL_PORT;
}

/* Perform the Sentinel mode initialization. */
void initSentinel(void) {
    int j;

    /* Remove usual Redis commands from the command table, then just add
     * the SENTINEL command. */
    dictEmpty(server.commands);
    for (j = 0; j < sizeof(sentinelcmds)/sizeof(sentinelcmds[0]); j++) {
        int retval;
        struct redisCommand *cmd = sentinelcmds+j;

        retval = dictAdd(server.commands, sdsnew(cmd->name), cmd);
        redisAssert(retval == DICT_OK);
    }

    /* Initialize various data structures. */
    sentinel.masters = dictCreate(&instancesDictType,NULL);
    sentinel.tilt = 0;
    sentinel.tilt_start_time = mstime();
    sentinel.previous_time = mstime();
    sentinel.running_scripts = 0;
    sentinel.scripts_queue = listCreate();
}

/* ============================== sentinelAddr ============================== */

/* Create a sentinelAddr object and return it on success.
 * On error NULL is returned and errno is set to:
 *  ENOENT: Can't resolve the hostname.
 *  EINVAL: Invalid port number.
 */
sentinelAddr *createSentinelAddr(char *hostname, int port) {
    char buf[32];
    sentinelAddr *sa;

    if (port <= 0 || port > 65535) {
        errno = EINVAL;
        return NULL;
    }
    if (anetResolve(NULL,hostname,buf) == ANET_ERR) {
        errno = ENOENT;
        return NULL;
    }
    sa = zmalloc(sizeof(*sa));
    sa->ip = sdsnew(buf);
    sa->port = port;
    return sa;
}

/* Free a Sentinel address. Can't fail. */
void releaseSentinelAddr(sentinelAddr *sa) {
    sdsfree(sa->ip);
    zfree(sa);
}

/* =========================== Events notification ========================== */

/* Send an event to log, pub/sub, user notification script.
 * 
 * 'level' is the log level for logging. Only REDIS_WARNING events will trigger
 * the execution of the user notification script.
 *
 * 'type' is the message type, also used as a pub/sub channel name.
 *
 * 'ri', is the redis instance target of this event if applicable, and is
 * used to obtain the path of the notification script to execute.
 *
 * The remaining arguments are printf-alike.
 * If the format specifier starts with the two characters "%@" then ri is
 * not NULL, and the message is prefixed with an instance identifier in the
 * following format:
 *
 *  <instance type> <instance name> <ip> <port>
 *
 *  If the instance type is not master, than the additional string is
 *  added to specify the originating master:
 *
 *  @ <master name> <master ip> <master port>
 *
 *  Any other specifier after "%@" is processed by printf itself.
 */
void sentinelEvent(int level, char *type, sentinelRedisInstance *ri,
                   const char *fmt, ...) {
    va_list ap;
    char msg[REDIS_MAX_LOGMSG_LEN];
    robj *channel, *payload;

    /* Handle %@ */
    if (fmt[0] == '%' && fmt[1] == '@') {
        sentinelRedisInstance *master = (ri->flags & SRI_MASTER) ?
                                         NULL : ri->master;

        if (master) {
            snprintf(msg, sizeof(msg), "%s %s %s %d @ %s %s %d",
                sentinelRedisInstanceTypeStr(ri),
                ri->name, ri->addr->ip, ri->addr->port,
                master->name, master->addr->ip, master->addr->port);
        } else {
            snprintf(msg, sizeof(msg), "%s %s %s %d",
                sentinelRedisInstanceTypeStr(ri),
                ri->name, ri->addr->ip, ri->addr->port);
        }
        fmt += 2;
    } else {
        msg[0] = '\0';
    }

    /* Use vsprintf for the rest of the formatting if any. */
    if (fmt[0] != '\0') {
        va_start(ap, fmt);
        vsnprintf(msg+strlen(msg), sizeof(msg)-strlen(msg), fmt, ap);
        va_end(ap);
    }

    /* Log the message if the log level allows it to be logged. */
    if (level >= server.verbosity)
        redisLog(level,"%s %s",type,msg);

    /* Publish the message via Pub/Sub if it's not a debugging one. */
    if (level != REDIS_DEBUG) {
        channel = createStringObject(type,strlen(type));
        payload = createStringObject(msg,strlen(msg));
        pubsubPublishMessage(channel,payload);
        decrRefCount(channel);
        decrRefCount(payload);
    }

    /* Call the notification script if applicable. */
    if (level == REDIS_WARNING && ri != NULL) {
        sentinelRedisInstance *master = (ri->flags & SRI_MASTER) ?
                                         ri : ri->master;
        if (master->notification_script) {
            sentinelScheduleScriptExecution(master->notification_script,
                type,msg,NULL);
        }
    }
}

/* ============================ script execution ============================ */

/* Release a script job structure and all the associated data. */
void sentinelReleaseScriptJob(sentinelScriptJob *sj) {
    int j = 0;

    while(sj->argv[j]) sdsfree(sj->argv[j++]);
    zfree(sj->argv);
    zfree(sj);
}

#define SENTINEL_SCRIPT_MAX_ARGS 16
void sentinelScheduleScriptExecution(char *path, ...) {
    va_list ap;
    char *argv[SENTINEL_SCRIPT_MAX_ARGS+1];
    int argc = 1;
    sentinelScriptJob *sj;

    va_start(ap, path);
    while(argc < SENTINEL_SCRIPT_MAX_ARGS) {
        argv[argc] = va_arg(ap,char*);
        if (!argv[argc]) break;
        argv[argc] = sdsnew(argv[argc]); /* Copy the string. */
        argc++;
    }
    va_end(ap);
    argv[0] = sdsnew(path);
    
    sj = zmalloc(sizeof(*sj));
    sj->flags = SENTINEL_SCRIPT_NONE;
    sj->retry_num = 0;
    sj->argv = zmalloc(sizeof(char*)*(argc+1));
    sj->start_time = 0;
    sj->pid = 0;
    memcpy(sj->argv,argv,sizeof(char*)*(argc+1));

    listAddNodeTail(sentinel.scripts_queue,sj);

    /* Remove the oldest non running script if we already hit the limit. */
    if (listLength(sentinel.scripts_queue) > SENTINEL_SCRIPT_MAX_QUEUE) {
        listNode *ln;
        listIter li;

        listRewind(sentinel.scripts_queue,&li);
        while ((ln = listNext(&li)) != NULL) {
            sj = ln->value;

            if (sj->flags & SENTINEL_SCRIPT_RUNNING) continue;
            /* The first node is the oldest as we add on tail. */
            listDelNode(sentinel.scripts_queue,ln);
            sentinelReleaseScriptJob(sj);
            break;
        }
        redisAssert(listLength(sentinel.scripts_queue) <=
                    SENTINEL_SCRIPT_MAX_QUEUE);
    }
}

/* Lookup a script in the scripts queue via pid, and returns the list node
 * (so that we can easily remove it from the queue if needed). */
listNode *sentinelGetScriptListNodeByPid(pid_t pid) {
    listNode *ln;
    listIter li;

    listRewind(sentinel.scripts_queue,&li);
    while ((ln = listNext(&li)) != NULL) {
        sentinelScriptJob *sj = ln->value;

        if ((sj->flags & SENTINEL_SCRIPT_RUNNING) && sj->pid == pid)
            return ln;
    }
    return NULL;
}

/* Run pending scripts if we are not already at max number of running
 * scripts. */
void sentinelRunPendingScripts(void) {
    listNode *ln;
    listIter li;
    mstime_t now = mstime();

    /* Find jobs that are not running and run them, from the top to the
     * tail of the queue, so we run older jobs first. */
    listRewind(sentinel.scripts_queue,&li);
    while (sentinel.running_scripts < SENTINEL_SCRIPT_MAX_RUNNING &&
           (ln = listNext(&li)) != NULL)
    {
        sentinelScriptJob *sj = ln->value;
        pid_t pid;

        /* Skip if already running. */
        if (sj->flags & SENTINEL_SCRIPT_RUNNING) continue;

        /* Skip if it's a retry, but not enough time has elapsed. */
        if (sj->start_time && sj->start_time > now) continue;

        sj->flags |= SENTINEL_SCRIPT_RUNNING;
        sj->start_time = mstime();
        sj->retry_num++;
        pid = fork();

        if (pid == -1) {
            /* Parent (fork error).
             * We report fork errors as signal 99, in order to unify the
             * reporting with other kind of errors. */
            sentinelEvent(REDIS_WARNING,"-script-error",NULL,
                          "%s %d %d", sj->argv[0], 99, 0);
            sj->flags &= ~SENTINEL_SCRIPT_RUNNING;
            sj->pid = 0;
        } else if (pid == 0) {
            /* Child */
            execve(sj->argv[0],sj->argv,environ);
            /* If we are here an error occurred. */
            _exit(2); /* Don't retry execution. */
        } else {
            sentinel.running_scripts++;
            sj->pid = pid;
            sentinelEvent(REDIS_DEBUG,"+script-child",NULL,"%ld",(long)pid);
        }
    }
}

/* How much to delay the execution of a script that we need to retry after
 * an error?
 *
 * We double the retry delay for every further retry we do. So for instance
 * if RETRY_DELAY is set to 30 seconds and the max number of retries is 10
 * starting from the second attempt to execute the script the delays are:
 * 30 sec, 60 sec, 2 min, 4 min, 8 min, 16 min, 32 min, 64 min, 128 min. */
mstime_t sentinelScriptRetryDelay(int retry_num) {
    mstime_t delay = SENTINEL_SCRIPT_RETRY_DELAY;

    while (retry_num-- > 1) delay *= 2;
    return delay;
}

/* Check for scripts that terminated, and remove them from the queue if the
 * script terminated successfully. If instead the script was terminated by
 * a signal, or returned exit code "1", it is scheduled to run again if
 * the max number of retries did not already elapsed. */
void sentinelCollectTerminatedScripts(void) {
    int statloc;
    pid_t pid;

    while ((pid = wait3(&statloc,WNOHANG,NULL)) > 0) {
        int exitcode = WEXITSTATUS(statloc);
        int bysignal = 0;
        listNode *ln;
        sentinelScriptJob *sj;

        if (WIFSIGNALED(statloc)) bysignal = WTERMSIG(statloc);
        sentinelEvent(REDIS_DEBUG,"-script-child",NULL,"%ld %d %d",
            (long)pid, exitcode, bysignal);
        
        ln = sentinelGetScriptListNodeByPid(pid);
        if (ln == NULL) {
            redisLog(REDIS_WARNING,"wait3() returned a pid (%ld) we can't find in our scripts execution queue!", (long)pid);
            continue;
        }
        sj = ln->value;

        /* If the script was terminated by a signal or returns an
         * exit code of "1" (that means: please retry), we reschedule it
         * if the max number of retries is not already reached. */
        if ((bysignal || exitcode == 1) &&
            sj->retry_num != SENTINEL_SCRIPT_MAX_RETRY)
        {
            sj->flags &= ~SENTINEL_SCRIPT_RUNNING;
            sj->pid = 0;
            sj->start_time = mstime() +
                             sentinelScriptRetryDelay(sj->retry_num);
        } else {
            /* Otherwise let's remove the script, but log the event if the
             * execution did not terminated in the best of the ways. */
            if (bysignal || exitcode != 0) {
                sentinelEvent(REDIS_WARNING,"-script-error",NULL,
                              "%s %d %d", sj->argv[0], bysignal, exitcode);
            }
            listDelNode(sentinel.scripts_queue,ln);
            sentinelReleaseScriptJob(sj);
            sentinel.running_scripts--;
        }
    }
}

/* Kill scripts in timeout, they'll be collected by the
 * sentinelCollectTerminatedScripts() function. */
void sentinelKillTimedoutScripts(void) {
    listNode *ln;
    listIter li;
    mstime_t now = mstime();

    listRewind(sentinel.scripts_queue,&li);
    while ((ln = listNext(&li)) != NULL) {
        sentinelScriptJob *sj = ln->value;

        if (sj->flags & SENTINEL_SCRIPT_RUNNING &&
            (now - sj->start_time) > SENTINEL_SCRIPT_MAX_RUNTIME)
        {
            sentinelEvent(REDIS_WARNING,"-script-timeout",NULL,"%s %ld",
                sj->argv[0], (long)sj->pid);
            kill(sj->pid,SIGKILL);
        }
    }
}

/* Implements SENTINEL PENDING-SCRIPTS command. */
void sentinelPendingScriptsCommand(redisClient *c) {
    listNode *ln;
    listIter li;

    addReplyMultiBulkLen(c,listLength(sentinel.scripts_queue));
    listRewind(sentinel.scripts_queue,&li);
    while ((ln = listNext(&li)) != NULL) {
        sentinelScriptJob *sj = ln->value;
        int j = 0;

        addReplyMultiBulkLen(c,10);

        addReplyBulkCString(c,"argv");
        while (sj->argv[j]) j++;
        addReplyMultiBulkLen(c,j);
        j = 0;
        while (sj->argv[j]) addReplyBulkCString(c,sj->argv[j++]);

        addReplyBulkCString(c,"flags");
        addReplyBulkCString(c,
            (sj->flags & SENTINEL_SCRIPT_RUNNING) ? "running" : "scheduled");

        addReplyBulkCString(c,"pid");
        addReplyBulkLongLong(c,sj->pid);

        if (sj->flags & SENTINEL_SCRIPT_RUNNING) {
            addReplyBulkCString(c,"run-time");
            addReplyBulkLongLong(c,mstime() - sj->start_time);
        } else {
            mstime_t delay = sj->start_time ? (sj->start_time-mstime()) : 0;
            if (delay < 0) delay = 0;
            addReplyBulkCString(c,"run-delay");
            addReplyBulkLongLong(c,delay);
        }

        addReplyBulkCString(c,"retry-num");
        addReplyBulkLongLong(c,sj->retry_num);
    }
}

/* This function calls, if any, the client reconfiguration script with the
 * following parameters:
 *
 * <master-name> <role> <state> <from-ip> <from-port> <to-ip> <to-port>
 *
 * It is called every time a failover starts, ends, or is aborted.
 *
 * <state> is "start", "end" or "abort".
 * <role> is either "leader" or "observer".
 *
 * from/to fields are respectively master -> promoted slave addresses for
 * "start" and "end", or the reverse (promoted slave -> master) in case of
 * "abort".
 */
void sentinelCallClientReconfScript(sentinelRedisInstance *master, int role, char *state, sentinelAddr *from, sentinelAddr *to) {
    char fromport[32], toport[32];

    if (master->client_reconfig_script == NULL) return;
    ll2string(fromport,sizeof(fromport),from->port);
    ll2string(toport,sizeof(toport),to->port);
    sentinelScheduleScriptExecution(master->client_reconfig_script,
        master->name,
        (role == SENTINEL_LEADER) ? "leader" : "observer",
        state, from->ip, fromport, to->ip, toport, NULL);
}

/* ========================== sentinelRedisInstance ========================= */

/* Create a redis instance, the following fields must be populated by the
 * caller if needed:
 * runid: set to NULL but will be populated once INFO output is received.
 * info_refresh: is set to 0 to mean that we never received INFO so far.
 *
 * If SRI_MASTER is set into initial flags the instance is added to
 * sentinel.masters table.
 *
 * if SRI_SLAVE or SRI_SENTINEL is set then 'master' must be not NULL and the
 * instance is added into master->slaves or master->sentinels table.
 *
 * If the instance is a slave or sentinel, the name parameter is ignored and
 * is created automatically as hostname:port.
 *
 * The function fails if hostname can't be resolved or port is out of range.
 * When this happens NULL is returned and errno is set accordingly to the
 * createSentinelAddr() function.
 *
 * The function may also fail and return NULL with errno set to EBUSY if
 * a master or slave with the same name already exists. */
sentinelRedisInstance *createSentinelRedisInstance(char *name, int flags, char *hostname, int port, int quorum, sentinelRedisInstance *master) {
    sentinelRedisInstance *ri;
    sentinelAddr *addr;
    dict *table = NULL;
    char slavename[128], *sdsname;

    redisAssert(flags & (SRI_MASTER|SRI_SLAVE|SRI_SENTINEL));
    redisAssert((flags & SRI_MASTER) || master != NULL);

    /* Check address validity. */
    addr = createSentinelAddr(hostname,port);
    if (addr == NULL) return NULL;

    /* For slaves and sentinel we use ip:port as name. */
    if (flags & (SRI_SLAVE|SRI_SENTINEL)) {
        snprintf(slavename,sizeof(slavename),"%s:%d",hostname,port);
        name = slavename;
    }

    /* Make sure the entry is not duplicated. This may happen when the same
     * name for a master is used multiple times inside the configuration or
     * if we try to add multiple times a slave or sentinel with same ip/port
     * to a master. */
    if (flags & SRI_MASTER) table = sentinel.masters;
    else if (flags & SRI_SLAVE) table = master->slaves;
    else if (flags & SRI_SENTINEL) table = master->sentinels;
    sdsname = sdsnew(name);
    if (dictFind(table,sdsname)) {
        sdsfree(sdsname);
        errno = EBUSY;
        return NULL;
    }

    /* Create the instance object. */
    ri = zmalloc(sizeof(*ri));
    /* Note that all the instances are started in the disconnected state,
     * the event loop will take care of connecting them. */
    ri->flags = flags | SRI_DISCONNECTED;
    ri->name = sdsname;
    ri->runid = NULL;
    ri->addr = addr;
    ri->cc = NULL;
    ri->pc = NULL;
    ri->pending_commands = 0;
    ri->cc_conn_time = 0;
    ri->pc_conn_time = 0;
    ri->pc_last_activity = 0;
    ri->last_avail_time = mstime();
    ri->last_pong_time = mstime();
    ri->last_pub_time = mstime();
    ri->last_hello_time = mstime();
    ri->last_master_down_reply_time = mstime();
    ri->s_down_since_time = 0;
    ri->o_down_since_time = 0;
    ri->down_after_period = master ? master->down_after_period :
                            SENTINEL_DOWN_AFTER_PERIOD;
    ri->master_link_down_time = 0;
    ri->auth_pass = NULL;
    ri->slave_priority = SENTINEL_DEFAULT_SLAVE_PRIORITY;
    ri->slave_reconf_sent_time = 0;
    ri->slave_master_host = NULL;
    ri->slave_master_port = 0;
    ri->slave_master_link_status = SENTINEL_MASTER_LINK_STATUS_DOWN;
    ri->sentinels = dictCreate(&instancesDictType,NULL);
    ri->quorum = quorum;
    ri->parallel_syncs = SENTINEL_DEFAULT_PARALLEL_SYNCS;
    ri->master = master;
    ri->slaves = dictCreate(&instancesDictType,NULL);
    ri->info_refresh = 0;

    /* Failover state. */
    ri->leader = NULL;
    ri->failover_state = SENTINEL_FAILOVER_STATE_NONE;
    ri->failover_state_change_time = 0;
    ri->failover_start_time = 0;
    ri->failover_timeout = SENTINEL_DEFAULT_FAILOVER_TIMEOUT;
    ri->promoted_slave = NULL;
    ri->notification_script = NULL;
    ri->client_reconfig_script = NULL;

    /* Add into the right table. */
    dictAdd(table, ri->name, ri);
    return ri;
}

/* Release this instance and all its slaves, sentinels, hiredis connections.
 * This function also takes care of unlinking the instance from the main
 * masters table (if it is a master) or from its master sentinels/slaves table
 * if it is a slave or sentinel. */
void releaseSentinelRedisInstance(sentinelRedisInstance *ri) {
    /* Release all its slaves or sentinels if any. */
    dictRelease(ri->sentinels);
    dictRelease(ri->slaves);

    /* Release hiredis connections. */
    if (ri->cc) sentinelKillLink(ri,ri->cc);
    if (ri->pc) sentinelKillLink(ri,ri->pc);

    /* Free other resources. */
    sdsfree(ri->name);
    sdsfree(ri->runid);
    sdsfree(ri->notification_script);
    sdsfree(ri->client_reconfig_script);
    sdsfree(ri->slave_master_host);
    sdsfree(ri->leader);
    sdsfree(ri->auth_pass);
    releaseSentinelAddr(ri->addr);

    /* Clear state into the master if needed. */
    if ((ri->flags & SRI_SLAVE) && (ri->flags & SRI_PROMOTED) && ri->master)
        ri->master->promoted_slave = NULL;

    zfree(ri);
}

/* Lookup a slave in a master Redis instance, by ip and port. */
sentinelRedisInstance *sentinelRedisInstanceLookupSlave(
                sentinelRedisInstance *ri, char *ip, int port)
{
    sds key;
    sentinelRedisInstance *slave;
  
    redisAssert(ri->flags & SRI_MASTER);
    key = sdscatprintf(sdsempty(),"%s:%d",ip,port);
    slave = dictFetchValue(ri->slaves,key);
    sdsfree(key);
    return slave;
}

/* Return the name of the type of the instance as a string. */
const char *sentinelRedisInstanceTypeStr(sentinelRedisInstance *ri) {
    if (ri->flags & SRI_MASTER) return "master";
    else if (ri->flags & SRI_SLAVE) return "slave";
    else if (ri->flags & SRI_SENTINEL) return "sentinel";
    else return "unknown";
}

/* This function removes all the instances found in the dictionary of instances
 * 'd', having either:
 * 
 * 1) The same ip/port as specified.
 * 2) The same runid.
 *
 * "1" and "2" don't need to verify at the same time, just one is enough.
 * If "runid" is NULL it is not checked.
 * Similarly if "ip" is NULL it is not checked.
 *
 * This function is useful because every time we add a new Sentinel into
 * a master's Sentinels dictionary, we want to be very sure about not
 * having duplicated instances for any reason. This is so important because
 * we use those other sentinels in order to run our quorum protocol to
 * understand if it's time to proceeed with the fail over.
 *
 * Making sure no duplication is possible we greately improve the robustness
 * of the quorum (otherwise we may end counting the same instance multiple
 * times for some reason).
 *
 * The function returns the number of Sentinels removed. */
int removeMatchingSentinelsFromMaster(sentinelRedisInstance *master, char *ip, int port, char *runid) {
    dictIterator *di;
    dictEntry *de;
    int removed = 0;

    di = dictGetSafeIterator(master->sentinels);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);

        if ((ri->runid && runid && strcmp(ri->runid,runid) == 0) ||
            (ip && strcmp(ri->addr->ip,ip) == 0 && port == ri->addr->port))
        {
            dictDelete(master->sentinels,ri->name);
            removed++;
        }
    }
    dictReleaseIterator(di);
    return removed;
}

/* Search an instance with the same runid, ip and port into a dictionary
 * of instances. Return NULL if not found, otherwise return the instance
 * pointer.
 *
 * runid or ip can be NULL. In such a case the search is performed only
 * by the non-NULL field. */
sentinelRedisInstance *getSentinelRedisInstanceByAddrAndRunID(dict *instances, char *ip, int port, char *runid) {
    dictIterator *di;
    dictEntry *de;
    sentinelRedisInstance *instance = NULL;

    redisAssert(ip || runid);   /* User must pass at least one search param. */
    di = dictGetIterator(instances);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);

        if (runid && !ri->runid) continue;
        if ((runid == NULL || strcmp(ri->runid, runid) == 0) &&
            (ip == NULL || (strcmp(ri->addr->ip, ip) == 0 &&
                            ri->addr->port == port)))
        {
            instance = ri;
            break;
        }
    }
    dictReleaseIterator(di);
    return instance;
}

/* Simple master lookup by name */
sentinelRedisInstance *sentinelGetMasterByName(char *name) {
    sentinelRedisInstance *ri;
    sds sdsname = sdsnew(name);

    ri = dictFetchValue(sentinel.masters,sdsname);
    sdsfree(sdsname);
    return ri;
}

/* Add the specified flags to all the instances in the specified dictionary. */
void sentinelAddFlagsToDictOfRedisInstances(dict *instances, int flags) {
    dictIterator *di;
    dictEntry *de;

    di = dictGetIterator(instances);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);
        ri->flags |= flags;
    }
    dictReleaseIterator(di);
}

/* Remove the specified flags to all the instances in the specified
 * dictionary. */
void sentinelDelFlagsToDictOfRedisInstances(dict *instances, int flags) {
    dictIterator *di;
    dictEntry *de;

    di = dictGetIterator(instances);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);
        ri->flags &= ~flags;
    }
    dictReleaseIterator(di);
}

/* Reset the state of a monitored master:
 * 1) Remove all slaves.
 * 2) Remove all sentinels.
 * 3) Remove most of the flags resulting from runtime operations.
 * 4) Reset timers to their default value.
 * 5) In the process of doing this undo the failover if in progress.
 * 6) Disconnect the connections with the master (will reconnect automatically).
 */
void sentinelResetMaster(sentinelRedisInstance *ri, int flags) {
    redisAssert(ri->flags & SRI_MASTER);
    dictRelease(ri->slaves);
    dictRelease(ri->sentinels);
    ri->slaves = dictCreate(&instancesDictType,NULL);
    ri->sentinels = dictCreate(&instancesDictType,NULL);
    if (ri->cc) sentinelKillLink(ri,ri->cc);
    if (ri->pc) sentinelKillLink(ri,ri->pc);
    ri->flags &= SRI_MASTER|SRI_CAN_FAILOVER|SRI_DISCONNECTED;
    if (ri->leader) {
        sdsfree(ri->leader);
        ri->leader = NULL;
    }
    ri->failover_state = SENTINEL_FAILOVER_STATE_NONE;
    ri->failover_state_change_time = 0;
    ri->failover_start_time = 0;
    ri->promoted_slave = NULL;
    sdsfree(ri->runid);
    sdsfree(ri->slave_master_host);
    ri->runid = NULL;
    ri->slave_master_host = NULL;
    ri->last_avail_time = mstime();
    ri->last_pong_time = mstime();
    if (flags & SENTINEL_GENERATE_EVENT)
        sentinelEvent(REDIS_WARNING,"+reset-master",ri,"%@");
}

/* Call sentinelResetMaster() on every master with a name matching the specified
 * pattern. */
int sentinelResetMastersByPattern(char *pattern, int flags) {
    dictIterator *di;
    dictEntry *de;
    int reset = 0;

    di = dictGetIterator(sentinel.masters);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);

        if (ri->name) {
            if (stringmatch(pattern,ri->name,0)) {
                sentinelResetMaster(ri,flags);
                reset++;
            }
        }
    }
    dictReleaseIterator(di);
    return reset;
}

/* Reset the specified master with sentinelResetMaster(), and also change
 * the ip:port address, but take the name of the instance unmodified.
 *
 * This is used to handle the +switch-master and +redirect-to-master events.
 *
 * The function returns REDIS_ERR if the address can't be resolved for some
 * reason. Otherwise REDIS_OK is returned.
 *
 * TODO: make this reset so that original sentinels are re-added with
 * same ip / port / runid.
 */

int sentinelResetMasterAndChangeAddress(sentinelRedisInstance *master, char *ip, int port) {
    sentinelAddr *oldaddr, *newaddr;

    newaddr = createSentinelAddr(ip,port);
    if (newaddr == NULL) return REDIS_ERR;
    sentinelResetMaster(master,SENTINEL_NO_FLAGS);
    oldaddr = master->addr;
    master->addr = newaddr;
    /* Release the old address at the end so we are safe even if the function
     * gets the master->addr->ip and master->addr->port as arguments. */
    releaseSentinelAddr(oldaddr);
    return REDIS_OK;
}

/* ============================ Config handling ============================= */
char *sentinelHandleConfiguration(char **argv, int argc) {
    sentinelRedisInstance *ri;

    if (!strcasecmp(argv[0],"monitor") && argc == 5) {
        /* monitor <name> <host> <port> <quorum> */
        int quorum = atoi(argv[4]);

        if (quorum <= 0) return "Quorum must be 1 or greater.";
        if (createSentinelRedisInstance(argv[1],SRI_MASTER,argv[2],
                                        atoi(argv[3]),quorum,NULL) == NULL)
        {
            switch(errno) {
            case EBUSY: return "Duplicated master name.";
            case ENOENT: return "Can't resolve master instance hostname.";
            case EINVAL: return "Invalid port number";
            }
        }
    } else if (!strcasecmp(argv[0],"down-after-milliseconds") && argc == 3) {
        /* down-after-milliseconds <name> <milliseconds> */
        ri = sentinelGetMasterByName(argv[1]);
        if (!ri) return "No such master with specified name.";
        ri->down_after_period = atoi(argv[2]);
        if (ri->down_after_period <= 0)
            return "negative or zero time parameter.";
    } else if (!strcasecmp(argv[0],"failover-timeout") && argc == 3) {
        /* failover-timeout <name> <milliseconds> */
        ri = sentinelGetMasterByName(argv[1]);
        if (!ri) return "No such master with specified name.";
        ri->failover_timeout = atoi(argv[2]);
        if (ri->failover_timeout <= 0)
            return "negative or zero time parameter.";
    } else if (!strcasecmp(argv[0],"can-failover") && argc == 3) {
        /* can-failover <name> <yes/no> */
        int yesno = yesnotoi(argv[2]);

        ri = sentinelGetMasterByName(argv[1]);
        if (!ri) return "No such master with specified name.";
        if (yesno == -1) return "Argument must be either yes or no.";
        if (yesno)
            ri->flags |= SRI_CAN_FAILOVER;
        else
            ri->flags &= ~SRI_CAN_FAILOVER;
   } else if (!strcasecmp(argv[0],"parallel-syncs") && argc == 3) {
        /* parallel-syncs <name> <milliseconds> */
        ri = sentinelGetMasterByName(argv[1]);
        if (!ri) return "No such master with specified name.";
        ri->parallel_syncs = atoi(argv[2]);
   } else if (!strcasecmp(argv[0],"notification-script") && argc == 3) {
        /* notification-script <name> <path> */
        ri = sentinelGetMasterByName(argv[1]);
        if (!ri) return "No such master with specified name.";
        if (access(argv[2],X_OK) == -1)
            return "Notification script seems non existing or non executable.";
        ri->notification_script = sdsnew(argv[2]);
   } else if (!strcasecmp(argv[0],"client-reconfig-script") && argc == 3) {
        /* client-reconfig-script <name> <path> */
        ri = sentinelGetMasterByName(argv[1]);
        if (!ri) return "No such master with specified name.";
        if (access(argv[2],X_OK) == -1)
            return "Client reconfiguration script seems non existing or "
                   "non executable.";
        ri->client_reconfig_script = sdsnew(argv[2]);
   } else if (!strcasecmp(argv[0],"auth-pass") && argc == 3) {
        /* auth-pass <name> <password> */
        ri = sentinelGetMasterByName(argv[1]);
        if (!ri) return "No such master with specified name.";
        ri->auth_pass = sdsnew(argv[2]);
    } else {
        return "Unrecognized sentinel configuration statement.";
    }
    return NULL;
}

/* ====================== hiredis connection handling ======================= */

/* Completely disconnect an hiredis link from an instance. */
void sentinelKillLink(sentinelRedisInstance *ri, redisAsyncContext *c) {
    if (ri->cc == c) {
        ri->cc = NULL;
        ri->pending_commands = 0;
    }
    if (ri->pc == c) ri->pc = NULL;
    c->data = NULL;
    ri->flags |= SRI_DISCONNECTED;
    redisAsyncFree(c);
}

/* This function takes an hiredis context that is in an error condition
 * and make sure to mark the instance as disconnected performing the
 * cleanup needed.
 *
 * Note: we don't free the hiredis context as hiredis will do it for us
 * for async conenctions. */
void sentinelDisconnectInstanceFromContext(const redisAsyncContext *c) {
    sentinelRedisInstance *ri = c->data;
    int pubsub;

    if (ri == NULL) return; /* The instance no longer exists. */

    pubsub = (ri->pc == c);
    sentinelEvent(REDIS_DEBUG, pubsub ? "-pubsub-link" : "-cmd-link", ri,
        "%@ #%s", c->errstr);
    if (pubsub)
        ri->pc = NULL;
    else
        ri->cc = NULL;
    ri->flags |= SRI_DISCONNECTED;
}

void sentinelLinkEstablishedCallback(const redisAsyncContext *c, int status) {
    if (status != REDIS_OK) {
        sentinelDisconnectInstanceFromContext(c);
    } else {
        sentinelRedisInstance *ri = c->data;
        int pubsub = (ri->pc == c);

        sentinelEvent(REDIS_DEBUG, pubsub ? "+pubsub-link" : "+cmd-link", ri,
            "%@");
    }
}

void sentinelDisconnectCallback(const redisAsyncContext *c, int status) {
    sentinelDisconnectInstanceFromContext(c);
}

/* Send the AUTH command with the specified master password if needed.
 * Note that for slaves the password set for the master is used.
 *
 * We don't check at all if the command was successfully transmitted
 * to the instance as if it fails Sentinel will detect the instance down,
 * will disconnect and reconnect the link and so forth. */
void sentinelSendAuthIfNeeded(sentinelRedisInstance *ri, redisAsyncContext *c) {
    char *auth_pass = (ri->flags & SRI_MASTER) ? ri->auth_pass :
                                                 ri->master->auth_pass;

    if (auth_pass)
        redisAsyncCommand(c, sentinelDiscardReplyCallback, NULL, "AUTH %s",
            auth_pass);
}

/* Create the async connections for the specified instance if the instance
 * is disconnected. Note that the SRI_DISCONNECTED flag is set even if just
 * one of the two links (commands and pub/sub) is missing. */
void sentinelReconnectInstance(sentinelRedisInstance *ri) {
    if (!(ri->flags & SRI_DISCONNECTED)) return;

    /* Commands connection. */
    if (ri->cc == NULL) {
        ri->cc = redisAsyncConnect(ri->addr->ip,ri->addr->port);
        if (ri->cc->err) {
            sentinelEvent(REDIS_DEBUG,"-cmd-link-reconnection",ri,"%@ #%s",
                ri->cc->errstr);
            sentinelKillLink(ri,ri->cc);
        } else {
            ri->cc_conn_time = mstime();
            ri->cc->data = ri;
            redisAeAttach(server.el,ri->cc);
            redisAsyncSetConnectCallback(ri->cc,
                                            sentinelLinkEstablishedCallback);
            redisAsyncSetDisconnectCallback(ri->cc,
                                            sentinelDisconnectCallback);
            sentinelSendAuthIfNeeded(ri,ri->cc);
        }
    }
    /* Pub / Sub */
    if ((ri->flags & SRI_MASTER) && ri->pc == NULL) {
        ri->pc = redisAsyncConnect(ri->addr->ip,ri->addr->port);
        if (ri->pc->err) {
            sentinelEvent(REDIS_DEBUG,"-pubsub-link-reconnection",ri,"%@ #%s",
                ri->pc->errstr);
            sentinelKillLink(ri,ri->pc);
        } else {
            int retval;

            ri->pc_conn_time = mstime();
            ri->pc->data = ri;
            redisAeAttach(server.el,ri->pc);
            redisAsyncSetConnectCallback(ri->pc,
                                            sentinelLinkEstablishedCallback);
            redisAsyncSetDisconnectCallback(ri->pc,
                                            sentinelDisconnectCallback);
            sentinelSendAuthIfNeeded(ri,ri->pc);
            /* Now we subscribe to the Sentinels "Hello" channel. */
            retval = redisAsyncCommand(ri->pc,
                sentinelReceiveHelloMessages, NULL, "SUBSCRIBE %s",
                    SENTINEL_HELLO_CHANNEL);
            if (retval != REDIS_OK) {
                /* If we can't subscribe, the Pub/Sub connection is useless
                 * and we can simply disconnect it and try again. */
                sentinelKillLink(ri,ri->pc);
                return;
            }
        }
    }
    /* Clear the DISCONNECTED flags only if we have both the connections
     * (or just the commands connection if this is a slave or a
     * sentinel instance). */
    if (ri->cc && (ri->flags & (SRI_SLAVE|SRI_SENTINEL) || ri->pc))
        ri->flags &= ~SRI_DISCONNECTED;
}

/* ======================== Redis instances pinging  ======================== */

/* Process the INFO output from masters. */
void sentinelRefreshInstanceInfo(sentinelRedisInstance *ri, const char *info) {
    sds *lines;
    int numlines, j;
    int role = 0;
    int runid_changed = 0;  /* true if runid changed. */
    int first_runid = 0;    /* true if this is the first runid we receive. */

    /* The following fields must be reset to a given value in the case they
     * are not found at all in the INFO output. */
    ri->master_link_down_time = 0;

    /* Process line by line. */
    lines = sdssplitlen(info,strlen(info),"\r\n",2,&numlines);
    for (j = 0; j < numlines; j++) {
        sentinelRedisInstance *slave;
        sds l = lines[j];

        /* run_id:<40 hex chars>*/
        if (sdslen(l) >= 47 && !memcmp(l,"run_id:",7)) {
            if (ri->runid == NULL) {
                ri->runid = sdsnewlen(l+7,40);
                first_runid = 1;
            } else {
                if (strncmp(ri->runid,l+7,40) != 0) {
                    runid_changed = 1;
                    sentinelEvent(REDIS_NOTICE,"+reboot",ri,"%@");
                    sdsfree(ri->runid);
                    ri->runid = sdsnewlen(l+7,40);
                }
            }
        }

        /* slave0:<ip>,<port>,<state> */
        if ((ri->flags & SRI_MASTER) &&
            sdslen(l) >= 7 &&
            !memcmp(l,"slave",5) && isdigit(l[5]))
        {
            char *ip, *port, *end;

            ip = strchr(l,':'); if (!ip) continue;
            ip++; /* Now ip points to start of ip address. */
            port = strchr(ip,','); if (!port) continue;
            *port = '\0'; /* nul term for easy access. */
            port++; /* Now port points to start of port number. */
            end = strchr(port,','); if (!end) continue;
            *end = '\0'; /* nul term for easy access. */

            /* Check if we already have this slave into our table,
             * otherwise add it. */
            if (sentinelRedisInstanceLookupSlave(ri,ip,atoi(port)) == NULL) {
                if ((slave = createSentinelRedisInstance(NULL,SRI_SLAVE,ip,
                            atoi(port), ri->quorum,ri)) != NULL)
                {
                    sentinelEvent(REDIS_NOTICE,"+slave",slave,"%@");
                }
            }
        }

        /* master_link_down_since_seconds:<seconds> */
        if (sdslen(l) >= 32 &&
            !memcmp(l,"master_link_down_since_seconds",30))
        {
            ri->master_link_down_time = strtoll(l+31,NULL,10)*1000;
        }

        /* role:<role> */
        if (!memcmp(l,"role:master",11)) role = SRI_MASTER;
        else if (!memcmp(l,"role:slave",10)) role = SRI_SLAVE;

        if (role == SRI_SLAVE) {
            /* master_host:<host> */
            if (sdslen(l) >= 12 && !memcmp(l,"master_host:",12)) {
                sdsfree(ri->slave_master_host);
                ri->slave_master_host = sdsnew(l+12);
            }

            /* master_port:<port> */
            if (sdslen(l) >= 12 && !memcmp(l,"master_port:",12))
                ri->slave_master_port = atoi(l+12);
            
            /* master_link_status:<status> */
            if (sdslen(l) >= 19 && !memcmp(l,"master_link_status:",19)) {
                ri->slave_master_link_status =
                    (strcasecmp(l+19,"up") == 0) ?
                    SENTINEL_MASTER_LINK_STATUS_UP :
                    SENTINEL_MASTER_LINK_STATUS_DOWN;
            }

            /* slave_priority:<priority> */
            if (sdslen(l) >= 15 && !memcmp(l,"slave_priority:",15))
                ri->slave_priority = atoi(l+15);
        }
    }
    ri->info_refresh = mstime();
    sdsfreesplitres(lines,numlines);

    /* ---------------------------- Acting half ----------------------------- */
    if (sentinel.tilt) return;

    /* Act if a master turned into a slave. */
    if ((ri->flags & SRI_MASTER) && role == SRI_SLAVE) {
        if ((first_runid || runid_changed) && ri->slave_master_host) {
            /* If it is the first time we receive INFO from it, but it's
             * a slave while it was configured as a master, we want to monitor
             * its master instead. */
            sentinelEvent(REDIS_WARNING,"+redirect-to-master",ri,
                "%s %s %d %s %d",
                ri->name, ri->addr->ip, ri->addr->port,
                ri->slave_master_host, ri->slave_master_port);
            sentinelResetMasterAndChangeAddress(ri,ri->slave_master_host,
                                                   ri->slave_master_port);
            return;
        }
    }

    /* Act if a slave turned into a master. */
    if ((ri->flags & SRI_SLAVE) && role == SRI_MASTER) {
        if (!(ri->master->flags & SRI_FAILOVER_IN_PROGRESS) &&
            (runid_changed || first_runid))
        {
            /* If a slave turned into master but:
             *
             * 1) Failover not in progress.
             * 2) RunID hs changed, or its the first time we see an INFO output.
             * 
             * We assume this is a reboot with a wrong configuration.
             * Log the event and remove the slave. */
            int retval;

            sentinelEvent(REDIS_WARNING,"-slave-restart-as-master",ri,"%@ #removing it from the attached slaves");
            retval = dictDelete(ri->master->slaves,ri->name);
            redisAssert(retval == REDIS_OK);
            return;
        } else if (ri->flags & SRI_PROMOTED) {
            /* If this is a promoted slave we can change state to the
             * failover state machine. */
            if ((ri->master->flags & SRI_FAILOVER_IN_PROGRESS) &&
                (ri->master->flags & SRI_I_AM_THE_LEADER) &&
                (ri->master->failover_state ==
                    SENTINEL_FAILOVER_STATE_WAIT_PROMOTION))
            {
                ri->master->failover_state = SENTINEL_FAILOVER_STATE_RECONF_SLAVES;
                ri->master->failover_state_change_time = mstime();
                sentinelEvent(REDIS_WARNING,"+promoted-slave",ri,"%@");
                sentinelEvent(REDIS_WARNING,"+failover-state-reconf-slaves",
                    ri->master,"%@");
                sentinelCallClientReconfScript(ri->master,SENTINEL_LEADER,
                    "start",ri->master->addr,ri->addr);
            }
        } else if (!(ri->master->flags & SRI_FAILOVER_IN_PROGRESS) ||
                    ((ri->master->flags & SRI_FAILOVER_IN_PROGRESS) &&
                     (ri->master->flags & SRI_I_AM_THE_LEADER) &&
                     ri->master->failover_state ==
                     SENTINEL_FAILOVER_STATE_WAIT_START))
        {
            /* No failover in progress? Then it is the start of a failover
             * and we are an observer.
             *
             * We also do that if we are a leader doing a failover, in wait
             * start, but well, somebody else started before us. */

            if (ri->master->flags & SRI_FAILOVER_IN_PROGRESS) {
                sentinelEvent(REDIS_WARNING,"-failover-abort-race",
                                ri->master, "%@");
                sentinelAbortFailover(ri->master);
            }

            ri->master->flags |= SRI_FAILOVER_IN_PROGRESS;
            sentinelEvent(REDIS_WARNING,"+failover-detected",ri->master,"%@");
            ri->master->failover_state = SENTINEL_FAILOVER_STATE_DETECT_END;
            ri->master->failover_state_change_time = mstime();
            ri->master->promoted_slave = ri;
            ri->flags |= SRI_PROMOTED;
            sentinelCallClientReconfScript(ri->master,SENTINEL_OBSERVER,
                "start", ri->master->addr,ri->addr);
            /* We are an observer, so we can only assume that the leader
             * is reconfiguring the slave instances. For this reason we
             * set all the instances as RECONF_SENT waiting for progresses
             * on this side. */
            sentinelAddFlagsToDictOfRedisInstances(ri->master->slaves,
                SRI_RECONF_SENT);
        }
    }

    /* Detect if the slave that is in the process of being reconfigured
     * changed state. */
    if ((ri->flags & SRI_SLAVE) && role == SRI_SLAVE &&
        (ri->flags & (SRI_RECONF_SENT|SRI_RECONF_INPROG)))
    {
        /* SRI_RECONF_SENT -> SRI_RECONF_INPROG. */
        if ((ri->flags & SRI_RECONF_SENT) &&
            ri->slave_master_host &&
            strcmp(ri->slave_master_host,
                    ri->master->promoted_slave->addr->ip) == 0 &&
            ri->slave_master_port == ri->master->promoted_slave->addr->port)
        {
            ri->flags &= ~SRI_RECONF_SENT;
            ri->flags |= SRI_RECONF_INPROG;
            sentinelEvent(REDIS_NOTICE,"+slave-reconf-inprog",ri,"%@");
        }

        /* SRI_RECONF_INPROG -> SRI_RECONF_DONE */
        if ((ri->flags & SRI_RECONF_INPROG) &&
            ri->slave_master_link_status == SENTINEL_MASTER_LINK_STATUS_UP)
        {
            ri->flags &= ~SRI_RECONF_INPROG;
            ri->flags |= SRI_RECONF_DONE;
            sentinelEvent(REDIS_NOTICE,"+slave-reconf-done",ri,"%@");
            /* If we are moving forward (a new slave is now configured)
             * we update the change_time as we are conceptually passing
             * to the next slave. */
            ri->failover_state_change_time = mstime();
        }
    }
}

void sentinelInfoReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
    sentinelRedisInstance *ri = c->data;
    redisReply *r;

    if (ri) ri->pending_commands--;
    if (!reply || !ri) return;
    r = reply;

    if (r->type == REDIS_REPLY_STRING) {
        sentinelRefreshInstanceInfo(ri,r->str);
    }
}

/* Just discard the reply. We use this when we are not monitoring the return
 * value of the command but its effects directly. */
void sentinelDiscardReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
    sentinelRedisInstance *ri = c->data;

    if (ri) ri->pending_commands--;
}

void sentinelPingReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
    sentinelRedisInstance *ri = c->data;
    redisReply *r;

    if (ri) ri->pending_commands--;
    if (!reply || !ri) return;
    r = reply;

    if (r->type == REDIS_REPLY_STATUS ||
        r->type == REDIS_REPLY_ERROR) {
        /* Update the "instance available" field only if this is an
         * acceptable reply. */
        if (strncmp(r->str,"PONG",4) == 0 ||
            strncmp(r->str,"LOADING",7) == 0 ||
            strncmp(r->str,"MASTERDOWN",10) == 0)
        {
            ri->last_avail_time = mstime();
        } else {
            /* Send a SCRIPT KILL command if the instance appears to be
             * down because of a busy script. */
            if (strncmp(r->str,"BUSY",4) == 0 &&
                (ri->flags & SRI_S_DOWN) &&
                !(ri->flags & SRI_SCRIPT_KILL_SENT))
            {
                redisAsyncCommand(ri->cc,
                    sentinelDiscardReplyCallback, NULL, "SCRIPT KILL");
                ri->flags |= SRI_SCRIPT_KILL_SENT;
            }
        }
    }
    ri->last_pong_time = mstime();
}

/* This is called when we get the reply about the PUBLISH command we send
 * to the master to advertise this sentinel. */
void sentinelPublishReplyCallback(redisAsyncContext *c, void *reply, void *privdata) {
    sentinelRedisInstance *ri = c->data;
    redisReply *r;

    if (ri) ri->pending_commands--;
    if (!reply || !ri) return;
    r = reply;

    /* Only update pub_time if we actually published our message. Otherwise
     * we'll retry against in 100 milliseconds. */
    if (r->type != REDIS_REPLY_ERROR)
        ri->last_pub_time = mstime();
}

/* This is our Pub/Sub callback for the Hello channel. It's useful in order
 * to discover other sentinels attached at the same master. */
void sentinelReceiveHelloMessages(redisAsyncContext *c, void *reply, void *privdata) {
    sentinelRedisInstance *ri = c->data;
    redisReply *r;

    if (!reply || !ri) return;
    r = reply;

    /* Update the last activity in the pubsub channel. Note that since we
     * receive our messages as well this timestamp can be used to detect
     * if the link is probably diconnected even if it seems otherwise. */
    ri->pc_last_activity = mstime();
   
    /* Sanity check in the reply we expect, so that the code that follows
     * can avoid to check for details. */
    if (r->type != REDIS_REPLY_ARRAY ||
        r->elements != 3 ||
        r->element[0]->type != REDIS_REPLY_STRING ||
        r->element[1]->type != REDIS_REPLY_STRING ||
        r->element[2]->type != REDIS_REPLY_STRING ||
        strcmp(r->element[0]->str,"message") != 0) return;

    /* We are not interested in meeting ourselves */
    if (strstr(r->element[2]->str,server.runid) != NULL) return;

    {
        int numtokens, port, removed, canfailover;
        char **token = sdssplitlen(r->element[2]->str,
                                   r->element[2]->len,
                                   ":",1,&numtokens);
        sentinelRedisInstance *sentinel;

        if (numtokens == 4) {
            /* First, try to see if we already have this sentinel. */
            port = atoi(token[1]);
            canfailover = atoi(token[3]);
            sentinel = getSentinelRedisInstanceByAddrAndRunID(
                            ri->sentinels,token[0],port,token[2]);

            if (!sentinel) {
                /* If not, remove all the sentinels that have the same runid
                 * OR the same ip/port, because it's either a restart or a
                 * network topology change. */
                removed = removeMatchingSentinelsFromMaster(ri,token[0],port,
                                token[2]);
                if (removed) {
                    sentinelEvent(REDIS_NOTICE,"-dup-sentinel",ri,
                        "%@ #duplicate of %s:%d or %s",
                        token[0],port,token[2]);
                }

                /* Add the new sentinel. */
                sentinel = createSentinelRedisInstance(NULL,SRI_SENTINEL,
                                token[0],port,ri->quorum,ri);
                if (sentinel) {
                    sentinelEvent(REDIS_NOTICE,"+sentinel",sentinel,"%@");
                    /* The runid is NULL after a new instance creation and
                     * for Sentinels we don't have a later chance to fill it,
                     * so do it now. */
                    sentinel->runid = sdsnew(token[2]);
                }
            }

            /* Update the state of the Sentinel. */
            if (sentinel) {
                sentinel->last_hello_time = mstime();
                if (canfailover)
                    sentinel->flags |= SRI_CAN_FAILOVER;
                else
                    sentinel->flags &= ~SRI_CAN_FAILOVER;
            }
        }
        sdsfreesplitres(token,numtokens);
    }
}

void sentinelPingInstance(sentinelRedisInstance *ri) {
    mstime_t now = mstime();
    mstime_t info_period;
    int retval;

    /* Return ASAP if we have already a PING or INFO already pending, or
     * in the case the instance is not properly connected. */
    if (ri->flags & SRI_DISCONNECTED) return;

    /* For INFO, PING, PUBLISH that are not critical commands to send we
     * also have a limit of SENTINEL_MAX_PENDING_COMMANDS. We don't
     * want to use a lot of memory just because a link is not working
     * properly (note that anyway there is a redundant protection about this,
     * that is, the link will be disconnected and reconnected if a long
     * timeout condition is detected. */
    if (ri->pending_commands >= SENTINEL_MAX_PENDING_COMMANDS) return;

    /* If this is a slave of a master in O_DOWN condition we start sending
     * it INFO every second, instead of the usual SENTINEL_INFO_PERIOD
     * period. In this state we want to closely monitor slaves in case they
     * are turned into masters by another Sentinel, or by the sysadmin. */
    if ((ri->flags & SRI_SLAVE) &&
        (ri->master->flags & (SRI_O_DOWN|SRI_FAILOVER_IN_PROGRESS))) {
        info_period = 1000;
    } else {
        info_period = SENTINEL_INFO_PERIOD;
    }

    if ((ri->flags & SRI_SENTINEL) == 0 &&
        (ri->info_refresh == 0 ||
        (now - ri->info_refresh) > info_period))
    {
        /* Send INFO to masters and slaves, not sentinels. */
        retval = redisAsyncCommand(ri->cc,
            sentinelInfoReplyCallback, NULL, "INFO");
        if (retval != REDIS_OK) return;
        ri->pending_commands++;
    } else if ((now - ri->last_pong_time) > SENTINEL_PING_PERIOD) {
        /* Send PING to all the three kinds of instances. */
        retval = redisAsyncCommand(ri->cc,
            sentinelPingReplyCallback, NULL, "PING");
        if (retval != REDIS_OK) return;
        ri->pending_commands++;
    } else if ((ri->flags & SRI_MASTER) &&
               (now - ri->last_pub_time) > SENTINEL_PUBLISH_PERIOD)
    {
        /* PUBLISH hello messages only to masters. */
        struct sockaddr_in sa;
        socklen_t salen = sizeof(sa);

        if (getsockname(ri->cc->c.fd,(struct sockaddr*)&sa,&salen) != -1) {
            char myaddr[128];

            snprintf(myaddr,sizeof(myaddr),"%s:%d:%s:%d",
                inet_ntoa(sa.sin_addr), server.port, server.runid,
                (ri->flags & SRI_CAN_FAILOVER) != 0);
            retval = redisAsyncCommand(ri->cc,
                sentinelPublishReplyCallback, NULL, "PUBLISH %s %s",
                    SENTINEL_HELLO_CHANNEL,myaddr);
            if (retval != REDIS_OK) return;
            ri->pending_commands++;
        }
    }
}

/* =========================== SENTINEL command ============================= */

const char *sentinelFailoverStateStr(int state) {
    switch(state) {
    case SENTINEL_FAILOVER_STATE_NONE: return "none";
    case SENTINEL_FAILOVER_STATE_WAIT_START: return "wait_start";
    case SENTINEL_FAILOVER_STATE_SELECT_SLAVE: return "select_slave";
    case SENTINEL_FAILOVER_STATE_SEND_SLAVEOF_NOONE: return "send_slaveof_noone";
    case SENTINEL_FAILOVER_STATE_WAIT_PROMOTION: return "wait_promotion";
    case SENTINEL_FAILOVER_STATE_RECONF_SLAVES: return "reconf_slaves";
    case SENTINEL_FAILOVER_STATE_ALERT_CLIENTS: return "alert_clients";
    case SENTINEL_FAILOVER_STATE_DETECT_END: return "detect_end";
    case SENTINEL_FAILOVER_STATE_UPDATE_CONFIG: return "update_config";
    default: return "unknown";
    }
}

/* Redis instance to Redis protocol representation. */
void addReplySentinelRedisInstance(redisClient *c, sentinelRedisInstance *ri) {
    char *flags = sdsempty();
    void *mbl;
    int fields = 0;

    mbl = addDeferredMultiBulkLength(c);

    addReplyBulkCString(c,"name");
    addReplyBulkCString(c,ri->name);
    fields++;

    addReplyBulkCString(c,"ip");
    addReplyBulkCString(c,ri->addr->ip);
    fields++;

    addReplyBulkCString(c,"port");
    addReplyBulkLongLong(c,ri->addr->port);
    fields++;

    addReplyBulkCString(c,"runid");
    addReplyBulkCString(c,ri->runid ? ri->runid : "");
    fields++;

    addReplyBulkCString(c,"flags");
    if (ri->flags & SRI_S_DOWN) flags = sdscat(flags,"s_down,");
    if (ri->flags & SRI_O_DOWN) flags = sdscat(flags,"o_down,");
    if (ri->flags & SRI_MASTER) flags = sdscat(flags,"master,");
    if (ri->flags & SRI_SLAVE) flags = sdscat(flags,"slave,");
    if (ri->flags & SRI_SENTINEL) flags = sdscat(flags,"sentinel,");
    if (ri->flags & SRI_DISCONNECTED) flags = sdscat(flags,"disconnected,");
    if (ri->flags & SRI_MASTER_DOWN) flags = sdscat(flags,"master_down,");
    if (ri->flags & SRI_FAILOVER_IN_PROGRESS)
        flags = sdscat(flags,"failover_in_progress,");
    if (ri->flags & SRI_I_AM_THE_LEADER)
        flags = sdscat(flags,"i_am_the_leader,");
    if (ri->flags & SRI_PROMOTED) flags = sdscat(flags,"promoted,");
    if (ri->flags & SRI_RECONF_SENT) flags = sdscat(flags,"reconf_sent,");
    if (ri->flags & SRI_RECONF_INPROG) flags = sdscat(flags,"reconf_inprog,");
    if (ri->flags & SRI_RECONF_DONE) flags = sdscat(flags,"reconf_done,");

    if (sdslen(flags) != 0) flags = sdsrange(flags,0,-2); /* remove last "," */
    addReplyBulkCString(c,flags);
    sdsfree(flags);
    fields++;

    addReplyBulkCString(c,"pending-commands");
    addReplyBulkLongLong(c,ri->pending_commands);
    fields++;

    if (ri->flags & SRI_FAILOVER_IN_PROGRESS) {
        addReplyBulkCString(c,"failover-state");
        addReplyBulkCString(c,(char*)sentinelFailoverStateStr(ri->failover_state));
        fields++;
    }

    addReplyBulkCString(c,"last-ok-ping-reply");
    addReplyBulkLongLong(c,mstime() - ri->last_avail_time);
    fields++;

    addReplyBulkCString(c,"last-ping-reply");
    addReplyBulkLongLong(c,mstime() - ri->last_pong_time);
    fields++;

    if (ri->flags & SRI_S_DOWN) {
        addReplyBulkCString(c,"s-down-time");
        addReplyBulkLongLong(c,mstime()-ri->s_down_since_time);
        fields++;
    }

    if (ri->flags & SRI_O_DOWN) {
        addReplyBulkCString(c,"o-down-time");
        addReplyBulkLongLong(c,mstime()-ri->o_down_since_time);
        fields++;
    }

    /* Masters and Slaves */
    if (ri->flags & (SRI_MASTER|SRI_SLAVE)) {
        addReplyBulkCString(c,"info-refresh");
        addReplyBulkLongLong(c,mstime() - ri->info_refresh);
        fields++;
    }

    /* Only masters */
    if (ri->flags & SRI_MASTER) {
        addReplyBulkCString(c,"num-slaves");
        addReplyBulkLongLong(c,dictSize(ri->slaves));
        fields++;

        addReplyBulkCString(c,"num-other-sentinels");
        addReplyBulkLongLong(c,dictSize(ri->sentinels));
        fields++;

        addReplyBulkCString(c,"quorum");
        addReplyBulkLongLong(c,ri->quorum);
        fields++;
    }

    /* Only slaves */
    if (ri->flags & SRI_SLAVE) {
        addReplyBulkCString(c,"master-link-down-time");
        addReplyBulkLongLong(c,ri->master_link_down_time);
        fields++;

        addReplyBulkCString(c,"master-link-status");
        addReplyBulkCString(c,
            (ri->slave_master_link_status == SENTINEL_MASTER_LINK_STATUS_UP) ?
            "ok" : "err");
        fields++;

        addReplyBulkCString(c,"master-host");
        addReplyBulkCString(c,
            ri->slave_master_host ? ri->slave_master_host : "?");
        fields++;

        addReplyBulkCString(c,"master-port");
        addReplyBulkLongLong(c,ri->slave_master_port);
        fields++;

        addReplyBulkCString(c,"slave-priority");
        addReplyBulkLongLong(c,ri->slave_priority);
        fields++;
    }

    /* Only sentinels */
    if (ri->flags & SRI_SENTINEL) {
        addReplyBulkCString(c,"last-hello-message");
        addReplyBulkLongLong(c,mstime() - ri->last_hello_time);
        fields++;

        addReplyBulkCString(c,"can-failover-its-master");
        addReplyBulkLongLong(c,(ri->flags & SRI_CAN_FAILOVER) != 0);
        fields++;

        if (ri->flags & SRI_MASTER_DOWN) {
            addReplyBulkCString(c,"subjective-leader");
            addReplyBulkCString(c,ri->leader ? ri->leader : "?");
            fields++;
        }
    }

    setDeferredMultiBulkLength(c,mbl,fields*2);
}

/* Output a number of instances contanined inside a dictionary as
 * Redis protocol. */
void addReplyDictOfRedisInstances(redisClient *c, dict *instances) {
    dictIterator *di;
    dictEntry *de;

    di = dictGetIterator(instances);
    addReplyMultiBulkLen(c,dictSize(instances));
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);

        addReplySentinelRedisInstance(c,ri);
    }
    dictReleaseIterator(di);
}

/* Lookup the named master into sentinel.masters.
 * If the master is not found reply to the client with an error and returns
 * NULL. */
sentinelRedisInstance *sentinelGetMasterByNameOrReplyError(redisClient *c,
                        robj *name)
{
    sentinelRedisInstance *ri;

    ri = dictFetchValue(sentinel.masters,c->argv[2]->ptr);
    if (!ri) {
        addReplyError(c,"No such master with that name");
        return NULL;
    }
    return ri;
}

void sentinelCommand(redisClient *c) {
    if (!strcasecmp(c->argv[1]->ptr,"masters")) {
        /* SENTINEL MASTERS */
        if (c->argc != 2) goto numargserr;

        addReplyDictOfRedisInstances(c,sentinel.masters);
    } else if (!strcasecmp(c->argv[1]->ptr,"slaves")) {
        /* SENTINEL SLAVES <master-name> */
        sentinelRedisInstance *ri;

        if (c->argc != 3) goto numargserr;
        if ((ri = sentinelGetMasterByNameOrReplyError(c,c->argv[2])) == NULL)
            return;
        addReplyDictOfRedisInstances(c,ri->slaves);
    } else if (!strcasecmp(c->argv[1]->ptr,"sentinels")) {
        /* SENTINEL SENTINELS <master-name> */
        sentinelRedisInstance *ri;

        if (c->argc != 3) goto numargserr;
        if ((ri = sentinelGetMasterByNameOrReplyError(c,c->argv[2])) == NULL)
            return;
        addReplyDictOfRedisInstances(c,ri->sentinels);
    } else if (!strcasecmp(c->argv[1]->ptr,"is-master-down-by-addr")) {
        /* SENTINEL IS-MASTER-DOWN-BY-ADDR <ip> <port> */
        sentinelRedisInstance *ri;
        char *leader = NULL;
        long port;
        int isdown = 0;

        if (c->argc != 4) goto numargserr;
        if (getLongFromObjectOrReply(c,c->argv[3],&port,NULL) != REDIS_OK)
            return;
        ri = getSentinelRedisInstanceByAddrAndRunID(sentinel.masters,
            c->argv[2]->ptr,port,NULL);

        /* It exists? Is actually a master? Is subjectively down? It's down.
         * Note: if we are in tilt mode we always reply with "0". */
        if (!sentinel.tilt && ri && (ri->flags & SRI_S_DOWN) &&
                                    (ri->flags & SRI_MASTER))
            isdown = 1;
        if (ri) leader = sentinelGetSubjectiveLeader(ri);

        /* Reply with a two-elements multi-bulk reply: down state, leader. */
        addReplyMultiBulkLen(c,2);
        addReply(c, isdown ? shared.cone : shared.czero);
        addReplyBulkCString(c, leader ? leader : "?");
        if (leader) sdsfree(leader);
    } else if (!strcasecmp(c->argv[1]->ptr,"reset")) {
        /* SENTINEL RESET <pattern> */
        if (c->argc != 3) goto numargserr;
        addReplyLongLong(c,sentinelResetMastersByPattern(c->argv[2]->ptr,SENTINEL_GENERATE_EVENT));
    } else if (!strcasecmp(c->argv[1]->ptr,"get-master-addr-by-name")) {
        /* SENTINEL GET-MASTER-ADDR-BY-NAME <master-name> */
        sentinelRedisInstance *ri;

        if (c->argc != 3) goto numargserr;
        ri = sentinelGetMasterByName(c->argv[2]->ptr);
        if (ri == NULL) {
            addReply(c,shared.nullmultibulk);
        } else if (ri->info_refresh == 0) {
            addReplySds(c,sdsnew("-IDONTKNOW I have not enough information to reply. Please ask another Sentinel.\r\n"));
        } else {
            sentinelAddr *addr = ri->addr;

            if ((ri->flags & SRI_FAILOVER_IN_PROGRESS) && ri->promoted_slave)
                addr = ri->promoted_slave->addr;
            addReplyMultiBulkLen(c,2);
            addReplyBulkCString(c,addr->ip);
            addReplyBulkLongLong(c,addr->port);
        }
    } else if (!strcasecmp(c->argv[1]->ptr,"failover")) {
        /* SENTINEL FAILOVER <master-name> */
        sentinelRedisInstance *ri;

        if (c->argc != 3) goto numargserr;
        if ((ri = sentinelGetMasterByNameOrReplyError(c,c->argv[2])) == NULL)
            return;
        if (ri->flags & SRI_FAILOVER_IN_PROGRESS) {
            addReplySds(c,sdsnew("-INPROG Failover already in progress\r\n"));
            return;
        }
        if (sentinelSelectSlave(ri) == NULL) {
            addReplySds(c,sdsnew("-NOGOODSLAVE No suitable slave to promote\r\n"));
            return;
        }
        sentinelStartFailover(ri,SENTINEL_FAILOVER_STATE_WAIT_START);
        ri->flags |= SRI_FORCE_FAILOVER;
        addReply(c,shared.ok);
    } else if (!strcasecmp(c->argv[1]->ptr,"pending-scripts")) {
        /* SENTINEL PENDING-SCRIPTS */

        if (c->argc != 2) goto numargserr;
        sentinelPendingScriptsCommand(c);
    } else {
        addReplyErrorFormat(c,"Unknown sentinel subcommand '%s'",
                               (char*)c->argv[1]->ptr);
    }
    return;

numargserr:
    addReplyErrorFormat(c,"Wrong number of commands for 'sentinel %s'",
                          (char*)c->argv[1]->ptr);
}

void sentinelInfoCommand(redisClient *c) {
    char *section = c->argc == 2 ? c->argv[1]->ptr : "default";
    sds info = sdsempty();
    int defsections = !strcasecmp(section,"default");
    int sections = 0;

    if (c->argc > 2) {
        addReply(c,shared.syntaxerr);
        return;
    }

    if (!strcasecmp(section,"server") || defsections) {
        if (sections++) info = sdscat(info,"\r\n");
        sds serversection = genRedisInfoString("server");
        info = sdscatlen(info,serversection,sdslen(serversection));
        sdsfree(serversection);
    }

    if (!strcasecmp(section,"sentinel") || defsections) {
        dictIterator *di;
        dictEntry *de;
        int master_id = 0;

        if (sections++) info = sdscat(info,"\r\n");
        info = sdscatprintf(info,
            "# Sentinel\r\n"
            "sentinel_masters:%lu\r\n"
            "sentinel_tilt:%d\r\n"
            "sentinel_running_scripts:%d\r\n"
            "sentinel_scripts_queue_length:%ld\r\n",
            dictSize(sentinel.masters),
            sentinel.tilt,
            sentinel.running_scripts,
            listLength(sentinel.scripts_queue));

        di = dictGetIterator(sentinel.masters);
        while((de = dictNext(di)) != NULL) {
            sentinelRedisInstance *ri = dictGetVal(de);
            char *status = "ok";

            if (ri->flags & SRI_O_DOWN) status = "odown";
            else if (ri->flags & SRI_S_DOWN) status = "sdown";
            info = sdscatprintf(info,
                "master%d:name=%s,status=%s,address=%s:%d,"
                "slaves=%lu,sentinels=%lu\r\n",
                master_id++, ri->name, status,
                ri->addr->ip, ri->addr->port,
                dictSize(ri->slaves),
                dictSize(ri->sentinels)+1);
        }
        dictReleaseIterator(di);
    }

    addReplySds(c,sdscatprintf(sdsempty(),"$%lu\r\n",
        (unsigned long)sdslen(info)));
    addReplySds(c,info);
    addReply(c,shared.crlf);
}

/* ===================== SENTINEL availability checks ======================= */

/* Is this instance down from our point of view? */
void sentinelCheckSubjectivelyDown(sentinelRedisInstance *ri) {
    mstime_t elapsed = mstime() - ri->last_avail_time;

    /* Check if we are in need for a reconnection of one of the 
     * links, because we are detecting low activity.
     *
     * 1) Check if the command link seems connected, was connected not less
     *    than SENTINEL_MIN_LINK_RECONNECT_PERIOD, but still we have an
     *    idle time that is greater than down_after_period / 2 seconds. */
    if (ri->cc &&
        (mstime() - ri->cc_conn_time) > SENTINEL_MIN_LINK_RECONNECT_PERIOD &&
        (mstime() - ri->last_pong_time) > (ri->down_after_period/2))
    {
        sentinelKillLink(ri,ri->cc);
    }

    /* 2) Check if the pubsub link seems connected, was connected not less
     *    than SENTINEL_MIN_LINK_RECONNECT_PERIOD, but still we have no
     *    activity in the Pub/Sub channel for more than
     *    SENTINEL_PUBLISH_PERIOD * 3.
     */
    if (ri->pc &&
        (mstime() - ri->pc_conn_time) > SENTINEL_MIN_LINK_RECONNECT_PERIOD &&
        (mstime() - ri->pc_last_activity) > (SENTINEL_PUBLISH_PERIOD*3))
    {
        sentinelKillLink(ri,ri->pc);
    }

    /* Update the subjectively down flag. */
    if (elapsed > ri->down_after_period) {
        /* Is subjectively down */
        if ((ri->flags & SRI_S_DOWN) == 0) {
            sentinelEvent(REDIS_WARNING,"+sdown",ri,"%@");
            ri->s_down_since_time = mstime();
            ri->flags |= SRI_S_DOWN;
        }
    } else {
        /* Is subjectively up */
        if (ri->flags & SRI_S_DOWN) {
            sentinelEvent(REDIS_WARNING,"-sdown",ri,"%@");
            ri->flags &= ~(SRI_S_DOWN|SRI_SCRIPT_KILL_SENT);
        }
    }
}

/* Is this instance down accordingly to the configured quorum? */
void sentinelCheckObjectivelyDown(sentinelRedisInstance *master) {
    dictIterator *di;
    dictEntry *de;
    int quorum = 0, odown = 0;

    if (master->flags & SRI_S_DOWN) {
        /* Is down for enough sentinels? */
        quorum = 1; /* the current sentinel. */
        /* Count all the other sentinels. */
        di = dictGetIterator(master->sentinels);
        while((de = dictNext(di)) != NULL) {
            sentinelRedisInstance *ri = dictGetVal(de);

            if (ri->flags & SRI_MASTER_DOWN) quorum++;
        }
        dictReleaseIterator(di);
        if (quorum >= master->quorum) odown = 1;
    }

    /* Set the flag accordingly to the outcome. */
    if (odown) {
        if ((master->flags & SRI_O_DOWN) == 0) {
            sentinelEvent(REDIS_WARNING,"+odown",master,"%@ #quorum %d/%d",
                quorum, master->quorum);
            master->flags |= SRI_O_DOWN;
            master->o_down_since_time = mstime();
        }
    } else {
        if (master->flags & SRI_O_DOWN) {
            sentinelEvent(REDIS_WARNING,"-odown",master,"%@");
            master->flags &= ~SRI_O_DOWN;
        }
    }
}

/* Receive the SENTINEL is-master-down-by-addr reply, see the
 * sentinelAskMasterStateToOtherSentinels() function for more information. */
void sentinelReceiveIsMasterDownReply(redisAsyncContext *c, void *reply, void *privdata) {
    sentinelRedisInstance *ri = c->data;
    redisReply *r;

    if (ri) ri->pending_commands--;
    if (!reply || !ri) return;
    r = reply;

    /* Ignore every error or unexpected reply.
     * Note that if the command returns an error for any reason we'll
     * end clearing the SRI_MASTER_DOWN flag for timeout anyway. */
    if (r->type == REDIS_REPLY_ARRAY && r->elements == 2 &&
        r->element[0]->type == REDIS_REPLY_INTEGER &&
        r->element[1]->type == REDIS_REPLY_STRING)
    {
        ri->last_master_down_reply_time = mstime();
        if (r->element[0]->integer == 1) {
            ri->flags |= SRI_MASTER_DOWN;
        } else {
            ri->flags &= ~SRI_MASTER_DOWN;
        }
        sdsfree(ri->leader);
        ri->leader = sdsnew(r->element[1]->str);
    }
}

/* If we think (subjectively) the master is down, we start sending
 * SENTINEL IS-MASTER-DOWN-BY-ADDR requests to other sentinels
 * in order to get the replies that allow to reach the quorum and
 * possibly also mark the master as objectively down. */
void sentinelAskMasterStateToOtherSentinels(sentinelRedisInstance *master) {
    dictIterator *di;
    dictEntry *de;

    di = dictGetIterator(master->sentinels);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);
        mstime_t elapsed = mstime() - ri->last_master_down_reply_time;
        char port[32];
        int retval;

        /* If the master state from other sentinel is too old, we clear it. */
        if (elapsed > SENTINEL_INFO_VALIDITY_TIME) {
            ri->flags &= ~SRI_MASTER_DOWN;
            sdsfree(ri->leader);
            ri->leader = NULL;
        }

        /* Only ask if master is down to other sentinels if:
         *
         * 1) We believe it is down, or there is a failover in progress.
         * 2) Sentinel is connected.
         * 3) We did not received the info within SENTINEL_ASK_PERIOD ms. */
        if ((master->flags & (SRI_S_DOWN|SRI_FAILOVER_IN_PROGRESS)) == 0)
            continue;
        if (ri->flags & SRI_DISCONNECTED) continue;
        if (mstime() - ri->last_master_down_reply_time < SENTINEL_ASK_PERIOD)
            continue;

        /* Ask */
        ll2string(port,sizeof(port),master->addr->port);
        retval = redisAsyncCommand(ri->cc,
                    sentinelReceiveIsMasterDownReply, NULL,
                    "SENTINEL is-master-down-by-addr %s %s",
                    master->addr->ip, port);
        if (retval == REDIS_OK) ri->pending_commands++;
    }
    dictReleaseIterator(di);
}

/* =============================== FAILOVER ================================= */

/* Given a master get the "subjective leader", that is, among all the sentinels
 * with given characteristics, the one with the lexicographically smaller
 * runid. The characteristics required are:
 *
 * 1) Has SRI_CAN_FAILOVER flag.
 * 2) Is not disconnected.
 * 3) Recently answered to our ping (no longer than
 *    SENTINEL_INFO_VALIDITY_TIME milliseconds ago).
 *
 * The function returns a pointer to an sds string representing the runid of the
 * leader sentinel instance (from our point of view). Otherwise NULL is
 * returned if there are no suitable sentinels.
 */

int compareRunID(const void *a, const void *b) {
    char **aptrptr = (char**)a, **bptrptr = (char**)b;
    return strcasecmp(*aptrptr, *bptrptr);
}

char *sentinelGetSubjectiveLeader(sentinelRedisInstance *master) {
    dictIterator *di;
    dictEntry *de;
    char **instance =
        zmalloc(sizeof(char*)*(dictSize(master->sentinels)+1));
    int instances = 0;
    char *leader = NULL;

    if (master->flags & SRI_CAN_FAILOVER) {
        /* Add myself if I'm a Sentinel that can failover this master. */
        instance[instances++] = server.runid;
    }

    di = dictGetIterator(master->sentinels);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);
        mstime_t lag = mstime() - ri->last_avail_time;

        if (lag > SENTINEL_INFO_VALIDITY_TIME ||
            !(ri->flags & SRI_CAN_FAILOVER) ||
            (ri->flags & SRI_DISCONNECTED) ||
            ri->runid == NULL)
            continue;
        instance[instances++] = ri->runid;
    }
    dictReleaseIterator(di);

    /* If we have at least one instance passing our checks, order the array
     * by runid. */
    if (instances) {
        qsort(instance,instances,sizeof(char*),compareRunID);
        leader = sdsnew(instance[0]);
    }
    zfree(instance);
    return leader;
}

struct sentinelLeader {
    char *runid;
    unsigned long votes;
};

/* Helper function for sentinelGetObjectiveLeader, increment the counter
 * relative to the specified runid. */
void sentinelObjectiveLeaderIncr(dict *counters, char *runid) {
    dictEntry *de = dictFind(counters,runid);
    uint64_t oldval;

    if (de) {
        oldval = dictGetUnsignedIntegerVal(de);
        dictSetUnsignedIntegerVal(de,oldval+1);
    } else {
        de = dictAddRaw(counters,runid);
        redisAssert(de != NULL);
        dictSetUnsignedIntegerVal(de,1);
    }
}

/* Scan all the Sentinels attached to this master to check what is the
 * most voted leader among Sentinels. */
char *sentinelGetObjectiveLeader(sentinelRedisInstance *master) {
    dict *counters;
    dictIterator *di;
    dictEntry *de;
    unsigned int voters = 0, voters_quorum;
    char *myvote;
    char *winner = NULL;

    redisAssert(master->flags & (SRI_O_DOWN|SRI_FAILOVER_IN_PROGRESS));
    counters = dictCreate(&leaderVotesDictType,NULL);

    /* Count my vote. */
    myvote = sentinelGetSubjectiveLeader(master);
    if (myvote) {
        sentinelObjectiveLeaderIncr(counters,myvote);
        voters++;
    }

    /* Count other sentinels votes */
    di = dictGetIterator(master->sentinels);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);
        if (ri->leader == NULL) continue;
        /* If the failover is not already in progress we are only interested
         * in Sentinels that believe the master is down. Otherwise the leader
         * selection is useful for the "failover-takedown" when the original
         * leader fails. In that case we consider all the voters. */
        if (!(master->flags & SRI_FAILOVER_IN_PROGRESS) &&
            !(ri->flags & SRI_MASTER_DOWN)) continue;
        sentinelObjectiveLeaderIncr(counters,ri->leader);
        voters++;
    }
    dictReleaseIterator(di);
    voters_quorum = voters/2+1;

    /* Check what's the winner. For the winner to win, it needs two conditions:
     * 1) Absolute majority between voters (50% + 1).
     * 2) And anyway at least master->quorum votes. */
    {
        uint64_t max_votes = 0; /* Max votes so far. */

        di = dictGetIterator(counters);
        while((de = dictNext(di)) != NULL) {
            uint64_t votes = dictGetUnsignedIntegerVal(de);

            if (max_votes < votes) {
                max_votes = votes;
                winner = dictGetKey(de);
            }
        }
        dictReleaseIterator(di);
        if (winner && (max_votes < voters_quorum || max_votes < master->quorum))
            winner = NULL;
    }
    winner = winner ? sdsnew(winner) : NULL;
    sdsfree(myvote);
    dictRelease(counters);
    return winner;
}

/* Setup the master state to start a failover as a leader.
 *
 * State can be either:
 *
 * SENTINEL_FAILOVER_STATE_WAIT_START: starts a failover from scratch.
 * SENTINEL_FAILOVER_STATE_RECONF_SLAVES: takedown a failed failover.
 */
void sentinelStartFailover(sentinelRedisInstance *master, int state) {
    redisAssert(master->flags & SRI_MASTER);
    redisAssert(state == SENTINEL_FAILOVER_STATE_WAIT_START ||
                state == SENTINEL_FAILOVER_STATE_RECONF_SLAVES);

    master->failover_state = state;
    master->flags |= SRI_FAILOVER_IN_PROGRESS|SRI_I_AM_THE_LEADER;
    sentinelEvent(REDIS_WARNING,"+failover-triggered",master,"%@");

    /* Pick a random delay if it's a fresh failover (WAIT_START), and not
     * a recovery of a failover started by another sentinel. */
    if (master->failover_state == SENTINEL_FAILOVER_STATE_WAIT_START) {
        master->failover_start_time = mstime() +
            SENTINEL_FAILOVER_FIXED_DELAY +
            (rand() % SENTINEL_FAILOVER_MAX_RANDOM_DELAY);
        sentinelEvent(REDIS_WARNING,"+failover-state-wait-start",master,
            "%@ #starting in %lld milliseconds",
            master->failover_start_time-mstime());
    }
    master->failover_state_change_time = mstime();
}

/* This function checks if there are the conditions to start the failover,
 * that is:
 *
 * 1) Enough time has passed since O_DOWN.
 * 2) The master is marked as SRI_CAN_FAILOVER, so we can failover it.
 * 3) We are the objectively leader for this master.
 *
 * If the conditions are met we flag the master as SRI_FAILOVER_IN_PROGRESS
 * and SRI_I_AM_THE_LEADER.
 */
void sentinelStartFailoverIfNeeded(sentinelRedisInstance *master) {
    char *leader;
    int isleader;

    /* We can't failover if the master is not in O_DOWN state or if
     * there is not already a failover in progress (to perform the
     * takedown if the leader died) or if this Sentinel is not allowed
     * to start a failover. */
    if (!(master->flags & SRI_CAN_FAILOVER) ||
        !(master->flags & (SRI_O_DOWN|SRI_FAILOVER_IN_PROGRESS))) return;

    leader = sentinelGetObjectiveLeader(master);
    isleader = leader && strcasecmp(leader,server.runid) == 0;
    sdsfree(leader);

    /* If I'm not the leader, I can't failover for sure. */
    if (!isleader) return;

    /* If the failover is already in progress there are two options... */
    if (master->flags & SRI_FAILOVER_IN_PROGRESS) {
        if (master->flags & SRI_I_AM_THE_LEADER) {
            /* 1) I'm flagged as leader so I already started the failover.
             *    Just return. */
            return;
        } else {
            mstime_t elapsed = mstime() - master->failover_state_change_time;

            /* 2) I'm the new leader, but I'm not flagged as leader in the
             *    master: I did not started the failover, but the original
             *    leader has no longer the leadership.
             *
             *    In this case if the failover appears to be lagging
             *    for at least 25% of the configured failover timeout,
             *    I can assume I can take control. Otherwise
             *    it's better to return and wait more. */
            if (elapsed < (master->failover_timeout/4)) return;
            sentinelEvent(REDIS_WARNING,"+failover-takedown",master,"%@");
            /* We have already an elected slave if we are in
             * FAILOVER_IN_PROGRESS state, that is, the slave that we
             * observed turning into a master. */
            sentinelStartFailover(master,SENTINEL_FAILOVER_STATE_RECONF_SLAVES);
            /* As an observer we flagged all the slaves as RECONF_SENT but
             * now we are in charge of actually sending the reconfiguration
             * command so let's clear this flag for all the instances. */
            sentinelDelFlagsToDictOfRedisInstances(master->slaves,
                SRI_RECONF_SENT);
        }
    } else {
        /* Brand new failover as SRI_FAILOVER_IN_PROGRESS was not set.
         *
         * Do we have a slave to promote? Otherwise don't start a failover
         * at all. */
        if (sentinelSelectSlave(master) == NULL) return;
        sentinelStartFailover(master,SENTINEL_FAILOVER_STATE_WAIT_START);
    }
}

/* Select a suitable slave to promote. The current algorithm only uses
 * the following parameters:
 *
 * 1) None of the following conditions: S_DOWN, O_DOWN, DISCONNECTED.
 * 2) last_avail_time more recent than SENTINEL_INFO_VALIDITY_TIME.
 * 3) info_refresh more recent than SENTINEL_INFO_VALIDITY_TIME.
 * 4) master_link_down_time no more than:
 *     (now - master->s_down_since_time) + (master->down_after_period * 10).
 * 5) Slave priority can't be zero, otherwise the slave is discareded.
 *
 * Among all the slaves matching the above conditions we select the slave
 * with lower slave_priority. If priority is the same we select the slave
 * with lexicographically smaller runid.
 *
 * The function returns the pointer to the selected slave, otherwise
 * NULL if no suitable slave was found.
 */

int compareSlavesForPromotion(const void *a, const void *b) {
    sentinelRedisInstance **sa = (sentinelRedisInstance **)a,
                          **sb = (sentinelRedisInstance **)b;
    char *sa_runid, *sb_runid;

    if ((*sa)->slave_priority != (*sb)->slave_priority)
        return (*sa)->slave_priority - (*sb)->slave_priority;

    /* If priority is the same, select the slave with that has the
     * lexicographically smaller runid. Note that we try to handle runid
     * == NULL as there are old Redis versions that don't publish runid in
     * INFO. A NULL runid is considered bigger than any other runid. */
    sa_runid = (*sa)->runid;
    sb_runid = (*sb)->runid;
    if (sa_runid == NULL && sb_runid == NULL) return 0;
    else if (sa_runid == NULL) return 1;  /* a > b */
    else if (sb_runid == NULL) return -1; /* a < b */
    return strcasecmp(sa_runid, sb_runid);
}

sentinelRedisInstance *sentinelSelectSlave(sentinelRedisInstance *master) {
    sentinelRedisInstance **instance =
        zmalloc(sizeof(instance[0])*dictSize(master->slaves));
    sentinelRedisInstance *selected = NULL;
    int instances = 0;
    dictIterator *di;
    dictEntry *de;
    mstime_t max_master_down_time = 0;

    if (master->flags & SRI_S_DOWN)
        max_master_down_time += mstime() - master->s_down_since_time;
    max_master_down_time += master->down_after_period * 10;

    di = dictGetIterator(master->slaves);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *slave = dictGetVal(de);
        mstime_t info_validity_time = mstime()-SENTINEL_INFO_VALIDITY_TIME;

        if (slave->flags & (SRI_S_DOWN|SRI_O_DOWN|SRI_DISCONNECTED)) continue;
        if (slave->last_avail_time < info_validity_time) continue;
        if (slave->slave_priority == 0) continue;

        /* If the master is in SDOWN state we get INFO for slaves every second.
         * Otherwise we get it with the usual period so we need to account for
         * a larger delay. */
        if ((master->flags & SRI_S_DOWN) == 0)
            info_validity_time -= SENTINEL_INFO_PERIOD;
        if (slave->info_refresh < info_validity_time) continue;
        if (slave->master_link_down_time > max_master_down_time) continue;
        instance[instances++] = slave;
    }
    dictReleaseIterator(di);
    if (instances) {
        qsort(instance,instances,sizeof(sentinelRedisInstance*),
            compareSlavesForPromotion);
        selected = instance[0];
    }
    zfree(instance);
    return selected;
}

/* ---------------- Failover state machine implementation ------------------- */
void sentinelFailoverWaitStart(sentinelRedisInstance *ri) {
    /* If we in "wait start" but the master is no longer in ODOWN nor in
     * SDOWN condition we abort the failover. This is important as it
     * prevents a useless failover in a a notable case of netsplit, where
     * the senitnels are split from the redis instances. In this case
     * the failover will not start while there is the split because no
     * good slave can be reached. However when the split is resolved, we
     * can go to waitstart if the slave is back rechable a few milliseconds
     * before the master is. In that case when the master is back online
     * we cancel the failover. */
    if ((ri->flags & (SRI_S_DOWN|SRI_O_DOWN|SRI_FORCE_FAILOVER)) == 0) {
        sentinelEvent(REDIS_WARNING,"-failover-abort-master-is-back",
            ri,"%@");
        sentinelAbortFailover(ri);
        return;
    }

    /* Start the failover going to the next state if enough time has
     * elapsed. */
    if (mstime() >= ri->failover_start_time) {
        ri->failover_state = SENTINEL_FAILOVER_STATE_SELECT_SLAVE;
        ri->failover_state_change_time = mstime();
        sentinelEvent(REDIS_WARNING,"+failover-state-select-slave",ri,"%@");
    }
}

void sentinelFailoverSelectSlave(sentinelRedisInstance *ri) {
    sentinelRedisInstance *slave = sentinelSelectSlave(ri);

    if (slave == NULL) {
        sentinelEvent(REDIS_WARNING,"-failover-abort-no-good-slave",ri,"%@");
        sentinelAbortFailover(ri);
    } else {
        sentinelEvent(REDIS_WARNING,"+selected-slave",slave,"%@");
        slave->flags |= SRI_PROMOTED;
        ri->promoted_slave = slave;
        ri->failover_state = SENTINEL_FAILOVER_STATE_SEND_SLAVEOF_NOONE;
        ri->failover_state_change_time = mstime();
        sentinelEvent(REDIS_NOTICE,"+failover-state-send-slaveof-noone",
            slave, "%@");
    }
}

void sentinelFailoverSendSlaveOfNoOne(sentinelRedisInstance *ri) {
    int retval;

    if (ri->promoted_slave->flags & SRI_DISCONNECTED) return;

    /* Send SLAVEOF NO ONE command to turn the slave into a master.
     * We actually register a generic callback for this command as we don't
     * really care about the reply. We check if it worked indirectly observing
     * if INFO returns a different role (master instead of slave). */
    retval = redisAsyncCommand(ri->promoted_slave->cc,
        sentinelDiscardReplyCallback, NULL, "SLAVEOF NO ONE");
    if (retval != REDIS_OK) return;
    ri->promoted_slave->pending_commands++;
    sentinelEvent(REDIS_NOTICE, "+failover-state-wait-promotion",
        ri->promoted_slave,"%@");
    ri->failover_state = SENTINEL_FAILOVER_STATE_WAIT_PROMOTION;
    ri->failover_state_change_time = mstime();
}

/* We actually wait for promotion indirectly checking with INFO when the
 * slave turns into a master. */
void sentinelFailoverWaitPromotion(sentinelRedisInstance *ri) {
    mstime_t elapsed = mstime() - ri->failover_state_change_time;

    if (elapsed >= SENTINEL_PROMOTION_RETRY_PERIOD) {
        sentinelEvent(REDIS_WARNING,"-promotion-timeout",ri->promoted_slave,
            "%@");
        sentinelEvent(REDIS_WARNING,"+failover-state-select-slave",ri,"%@");
        ri->failover_state = SENTINEL_FAILOVER_STATE_SELECT_SLAVE;
        ri->failover_state_change_time = mstime();
        ri->promoted_slave->flags &= ~SRI_PROMOTED;
        ri->promoted_slave = NULL;
    }
}

void sentinelFailoverDetectEnd(sentinelRedisInstance *master) {
    int not_reconfigured = 0, timeout = 0;
    dictIterator *di;
    dictEntry *de;
    mstime_t elapsed = mstime() - master->failover_state_change_time;

    /* We can't consider failover finished if the promoted slave is
     * not reachable. */
    if (master->promoted_slave == NULL ||
        master->promoted_slave->flags & SRI_S_DOWN) return;

    /* The failover terminates once all the reachable slaves are properly
     * configured. */
    di = dictGetIterator(master->slaves);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *slave = dictGetVal(de);

        if (slave->flags & (SRI_PROMOTED|SRI_RECONF_DONE)) continue;
        if (slave->flags & SRI_S_DOWN) continue;
        not_reconfigured++;
    }
    dictReleaseIterator(di);

    /* Force end of failover on timeout. */
    if (elapsed > master->failover_timeout) {
        not_reconfigured = 0;
        timeout = 1;
        sentinelEvent(REDIS_WARNING,"+failover-end-for-timeout",master,"%@");
    }

    if (not_reconfigured == 0) {
        int role = (master->flags & SRI_I_AM_THE_LEADER) ? SENTINEL_LEADER :
                                                           SENTINEL_OBSERVER;

        sentinelEvent(REDIS_WARNING,"+failover-end",master,"%@");
        master->failover_state = SENTINEL_FAILOVER_STATE_UPDATE_CONFIG;
        master->failover_state_change_time = mstime();
        sentinelCallClientReconfScript(master,role,"end",master->addr,
            master->promoted_slave->addr);
    }

    /* If I'm the leader it is a good idea to send a best effort SLAVEOF
     * command to all the slaves still not reconfigured to replicate with
     * the new master. */
    if (timeout && (master->flags & SRI_I_AM_THE_LEADER)) {
        dictIterator *di;
        dictEntry *de;
        char master_port[32];

        ll2string(master_port,sizeof(master_port),
            master->promoted_slave->addr->port);

        di = dictGetIterator(master->slaves);
        while((de = dictNext(di)) != NULL) {
            sentinelRedisInstance *slave = dictGetVal(de);
            int retval;

            if (slave->flags &
                (SRI_RECONF_DONE|SRI_RECONF_SENT|SRI_DISCONNECTED)) continue;

            retval = redisAsyncCommand(slave->cc,
                sentinelDiscardReplyCallback, NULL, "SLAVEOF %s %s",
                    master->promoted_slave->addr->ip,
                    master_port);
            if (retval == REDIS_OK) {
                sentinelEvent(REDIS_NOTICE,"+slave-reconf-sent-be",slave,"%@");
                slave->flags |= SRI_RECONF_SENT;
            }
        }
        dictReleaseIterator(di);
    }
}

/* Send SLAVE OF <new master address> to all the remaining slaves that
 * still don't appear to have the configuration updated. */
void sentinelFailoverReconfNextSlave(sentinelRedisInstance *master) {
    dictIterator *di;
    dictEntry *de;
    int in_progress = 0;

    di = dictGetIterator(master->slaves);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *slave = dictGetVal(de);

        if (slave->flags & (SRI_RECONF_SENT|SRI_RECONF_INPROG))
            in_progress++;
    }
    dictReleaseIterator(di);

    di = dictGetIterator(master->slaves);
    while(in_progress < master->parallel_syncs &&
          (de = dictNext(di)) != NULL)
    {
        sentinelRedisInstance *slave = dictGetVal(de);
        int retval;
        char master_port[32];

        /* Skip the promoted slave, and already configured slaves. */
        if (slave->flags & (SRI_PROMOTED|SRI_RECONF_DONE)) continue;

        /* Clear the SRI_RECONF_SENT flag if too much time elapsed without
         * the slave moving forward to the next state. */
        if ((slave->flags & SRI_RECONF_SENT) &&
            (mstime() - slave->slave_reconf_sent_time) >
            SENTINEL_SLAVE_RECONF_RETRY_PERIOD)
        {
            sentinelEvent(REDIS_NOTICE,"-slave-reconf-sent-timeout",slave,"%@");
            slave->flags &= ~SRI_RECONF_SENT;
        }

        /* Nothing to do for instances that are disconnected or already
         * in RECONF_SENT state. */
        if (slave->flags & (SRI_DISCONNECTED|SRI_RECONF_SENT|SRI_RECONF_INPROG))
            continue;

        /* Send SLAVEOF <new master>. */
        ll2string(master_port,sizeof(master_port),
            master->promoted_slave->addr->port);
        retval = redisAsyncCommand(slave->cc,
            sentinelDiscardReplyCallback, NULL, "SLAVEOF %s %s",
                master->promoted_slave->addr->ip,
                master_port);
        if (retval == REDIS_OK) {
            slave->flags |= SRI_RECONF_SENT;
            slave->pending_commands++;
            slave->slave_reconf_sent_time = mstime();
            sentinelEvent(REDIS_NOTICE,"+slave-reconf-sent",slave,"%@");
            in_progress++;
        }
    }
    dictReleaseIterator(di);
    sentinelFailoverDetectEnd(master);
}

/* This function is called when the slave is in
 * SENTINEL_FAILOVER_STATE_UPDATE_CONFIG state. In this state we need
 * to remove it from the master table and add the promoted slave instead.
 *
 * If there are no promoted slaves as this instance is unique, we remove
 * and re-add it with the same address to trigger a complete state
 * refresh. */
void sentinelFailoverSwitchToPromotedSlave(sentinelRedisInstance *master) {
    sentinelRedisInstance *ref = master->promoted_slave ?
                                 master->promoted_slave : master;

    sentinelEvent(REDIS_WARNING,"+switch-master",master,"%s %s %d %s %d",
        master->name, master->addr->ip, master->addr->port,
        ref->addr->ip, ref->addr->port);

    sentinelResetMasterAndChangeAddress(master,ref->addr->ip,ref->addr->port);
}

void sentinelFailoverStateMachine(sentinelRedisInstance *ri) {
    redisAssert(ri->flags & SRI_MASTER);

    if (!(ri->flags & SRI_FAILOVER_IN_PROGRESS)) return;

    switch(ri->failover_state) {
        case SENTINEL_FAILOVER_STATE_WAIT_START:
            sentinelFailoverWaitStart(ri);
            break;
        case SENTINEL_FAILOVER_STATE_SELECT_SLAVE:
            sentinelFailoverSelectSlave(ri);
            break;
        case SENTINEL_FAILOVER_STATE_SEND_SLAVEOF_NOONE:
            sentinelFailoverSendSlaveOfNoOne(ri);
            break;
        case SENTINEL_FAILOVER_STATE_WAIT_PROMOTION:
            sentinelFailoverWaitPromotion(ri);
            break;
        case SENTINEL_FAILOVER_STATE_RECONF_SLAVES:
            sentinelFailoverReconfNextSlave(ri);
            break;
        case SENTINEL_FAILOVER_STATE_DETECT_END:
            sentinelFailoverDetectEnd(ri);
            break;
    }
}

/* Abort a failover in progress with the following steps:
 * 1) If this instance is the leaer send a SLAVEOF command to all the already
 *    reconfigured slaves if any to configure them to replicate with the
 *    original master.
 * 2) For both leaders and observers: clear the failover flags and state in
 *    the master instance.
 * 3) If there is already a promoted slave and we are the leader, and this
 *    slave is not DISCONNECTED, try to reconfigure it to replicate
 *    back to the master as well, sending a best effort SLAVEOF command.
 */
void sentinelAbortFailover(sentinelRedisInstance *ri) {
    char master_port[32];
    dictIterator *di;
    dictEntry *de;
    int sentinel_role;

    redisAssert(ri->flags & SRI_FAILOVER_IN_PROGRESS);
    ll2string(master_port,sizeof(master_port),ri->addr->port);

    /* Clear failover related flags from slaves.
     * Also if we are the leader make sure to send SLAVEOF commands to all the
     * already reconfigured slaves in order to turn them back into slaves of
     * the original master. */
    di = dictGetIterator(ri->slaves);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *slave = dictGetVal(de);
        if ((ri->flags & SRI_I_AM_THE_LEADER) &&
            !(slave->flags & SRI_DISCONNECTED) &&
             (slave->flags & (SRI_PROMOTED|SRI_RECONF_SENT|SRI_RECONF_INPROG|
                              SRI_RECONF_DONE)))
        {
            int retval;

            retval = redisAsyncCommand(slave->cc,
                sentinelDiscardReplyCallback, NULL, "SLAVEOF %s %s",
                    ri->addr->ip,
                    master_port);
            if (retval == REDIS_OK)
                sentinelEvent(REDIS_NOTICE,"-slave-reconf-undo",slave,"%@");
        }
        slave->flags &= ~(SRI_RECONF_SENT|SRI_RECONF_INPROG|SRI_RECONF_DONE);
    }
    dictReleaseIterator(di);

    sentinel_role = (ri->flags & SRI_I_AM_THE_LEADER) ? SENTINEL_LEADER :
                                                        SENTINEL_OBSERVER;
    ri->flags &= ~(SRI_FAILOVER_IN_PROGRESS|SRI_I_AM_THE_LEADER|SRI_FORCE_FAILOVER);
    ri->failover_state = SENTINEL_FAILOVER_STATE_NONE;
    ri->failover_state_change_time = mstime();
    if (ri->promoted_slave) {
        sentinelCallClientReconfScript(ri,sentinel_role,"abort",
            ri->promoted_slave->addr,ri->addr);
        ri->promoted_slave->flags &= ~SRI_PROMOTED;
        ri->promoted_slave = NULL;
    }
}

/* The following is called only for master instances and will abort the
 * failover process if:
 *
 * 1) The failover is in progress.
 * 2) We already promoted a slave.
 * 3) The promoted slave is in extended SDOWN condition.
 */
void sentinelAbortFailoverIfNeeded(sentinelRedisInstance *ri) {
    /* Failover is in progress? Do we have a promoted slave? */
    if (!(ri->flags & SRI_FAILOVER_IN_PROGRESS) || !ri->promoted_slave) return;

    /* Is the promoted slave into an extended SDOWN state? */
    if (!(ri->promoted_slave->flags & SRI_S_DOWN) ||
        (mstime() - ri->promoted_slave->s_down_since_time) <
        (ri->down_after_period * SENTINEL_EXTENDED_SDOWN_MULTIPLIER)) return;

    sentinelEvent(REDIS_WARNING,"-failover-abort-x-sdown",ri->promoted_slave,"%@");
    sentinelAbortFailover(ri);
}

/* ======================== SENTINEL timer handler ==========================
 * This is the "main" our Sentinel, being sentinel completely non blocking
 * in design. The function is called every second.
 * -------------------------------------------------------------------------- */

/* Perform scheduled operations for the specified Redis instance. */
void sentinelHandleRedisInstance(sentinelRedisInstance *ri) {
    /* ========== MONITORING HALF ============ */
    /* Every kind of instance */
    sentinelReconnectInstance(ri);
    sentinelPingInstance(ri);

    /* Masters and slaves */
    if (ri->flags & (SRI_MASTER|SRI_SLAVE)) {
        /* Nothing so far. */
    }

    /* Only masters */
    if (ri->flags & SRI_MASTER) {
        sentinelAskMasterStateToOtherSentinels(ri);
    }

    /* ============== ACTING HALF ============= */
    /* We don't proceed with the acting half if we are in TILT mode.
     * TILT happens when we find something odd with the time, like a
     * sudden change in the clock. */
    if (sentinel.tilt) {
        if (mstime()-sentinel.tilt_start_time < SENTINEL_TILT_PERIOD) return;
        sentinel.tilt = 0;
        sentinelEvent(REDIS_WARNING,"-tilt",NULL,"#tilt mode exited");
    }

    /* Every kind of instance */
    sentinelCheckSubjectivelyDown(ri);

    /* Masters and slaves */
    if (ri->flags & (SRI_MASTER|SRI_SLAVE)) {
        /* Nothing so far. */
    }

    /* Only masters */
    if (ri->flags & SRI_MASTER) {
        sentinelCheckObjectivelyDown(ri);
        sentinelStartFailoverIfNeeded(ri);
        sentinelFailoverStateMachine(ri);
        sentinelAbortFailoverIfNeeded(ri);
    }
}

/* Perform scheduled operations for all the instances in the dictionary.
 * Recursively call the function against dictionaries of slaves. */
void sentinelHandleDictOfRedisInstances(dict *instances) {
    dictIterator *di;
    dictEntry *de;
    sentinelRedisInstance *switch_to_promoted = NULL;

    /* There are a number of things we need to perform against every master. */
    di = dictGetIterator(instances);
    while((de = dictNext(di)) != NULL) {
        sentinelRedisInstance *ri = dictGetVal(de);

        sentinelHandleRedisInstance(ri);
        if (ri->flags & SRI_MASTER) {
            sentinelHandleDictOfRedisInstances(ri->slaves);
            sentinelHandleDictOfRedisInstances(ri->sentinels);
            if (ri->failover_state == SENTINEL_FAILOVER_STATE_UPDATE_CONFIG) {
                switch_to_promoted = ri;
            }
        }
    }
    if (switch_to_promoted)
        sentinelFailoverSwitchToPromotedSlave(switch_to_promoted);
    dictReleaseIterator(di);
}

/* This function checks if we need to enter the TITL mode.
 *
 * The TILT mode is entered if we detect that between two invocations of the
 * timer interrupt, a negative amount of time, or too much time has passed.
 * Note that we expect that more or less just 100 milliseconds will pass
 * if everything is fine. However we'll see a negative number or a
 * difference bigger than SENTINEL_TILT_TRIGGER milliseconds if one of the
 * following conditions happen:
 *
 * 1) The Sentiel process for some time is blocked, for every kind of
 * random reason: the load is huge, the computer was freezed for some time
 * in I/O or alike, the process was stopped by a signal. Everything.
 * 2) The system clock was altered significantly.
 *
 * Under both this conditions we'll see everything as timed out and failing
 * without good reasons. Instead we enter the TILT mode and wait
 * for SENTIENL_TILT_PERIOD to elapse before starting to act again.
 *
 * During TILT time we still collect information, we just do not act. */
void sentinelCheckTiltCondition(void) {
    mstime_t now = mstime();
    mstime_t delta = now - sentinel.previous_time;

    if (delta < 0 || delta > SENTINEL_TILT_TRIGGER) {
        sentinel.tilt = 1;
        sentinel.tilt_start_time = mstime();
        sentinelEvent(REDIS_WARNING,"+tilt",NULL,"#tilt mode entered");
    }
    sentinel.previous_time = mstime();
}

void sentinelTimer(void) {
    sentinelCheckTiltCondition();
    sentinelHandleDictOfRedisInstances(sentinel.masters);
    sentinelRunPendingScripts();
    sentinelCollectTerminatedScripts();
    sentinelKillTimedoutScripts();
}

Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.