1. Spiros Ioannou
  2. runcached

Overview

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RunCached

Execute commands while caching their output for subsequent calls. Command output will be cached for <cacheperiod> seconds and "replayed" for any subsequent calls. Original exit status will also be emulated.

Details

After cacheperiod has expired, command will be re-executed and a new result will be cached. Cache data is tied to the command and arguments executed and the path of the runcached executable. Cache results are stored in /tmp

You can use runcached to run resource-expensive commands multiple times, parsing different parts of its output each time. Those commands will be run only once for each cacheperiod.

Implementation is provided in 3 languages, python, C, BASH. Of course the BASH version is not really suggested but it works.

Usage

Python

runcached.py [-c cacheperiod] <command to execute with args>

C

runcached [-c cacheperiod] <command to execute with args>

Bash

runcached.sh <command to execute with args>

Examples

Example 1: Run the date command. Each time it executes prints the same date for 5 seconds.

runcached.py -c 5 date

Example 2: Zabbix userparameter which can be called multiple times , but actually executes only once every 20 seconds.

Query multiple parameters of mysql at the same time, without re-running the query.

UserParameter=mysql.globalstatus[*],/usr/local/bin/runcached.py -c 20 /usr/bin/mysql -ANe \"show global status\"|egrep '$1\b'|awk '{print $ 2}'

And then define some items like so:

Item Name                      Item Key
--------------                  --------------
MySQL DELETES       mysql.globalstatus[Com_delete]
MySQL INSERTS       mysql.globalstatus[Com_insert]
MySQL UPDATES       mysql.globalstatus[Com_update]
MySQL CREATE TABLE  mysql.globalstatus[Com_create_table]
MySQL SELECTS       mysql.globalstatus[Com_select]
MySQL Uptime        mysql.globalstatus[Uptime]
MySQL ALTER TABLE   mysql.globalstatus[Com_alter_table]

E.g. for DELETE: 
Type: Numeric, 
Data Type: Decimal. 
Units: QPS
Store Value: Delta (Speed per second)
Show Value: As Is