Cannot translate 'localhost' to IP address -- Success

[Former user]

environment：

Linux 192-168-0-174 3.10.0-327.59.59.46.h38.x86_64 #1 SMP Mon Dec 11 19:34:45 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

monit configuration:

set daemon 40
set logfile /var/paas/monit/monit.log
set httpd unixsocket /var/paas/monit/monit.sock and
    allow localhost

include /var/paas/monit/job/*.monitrc

description：

when do the test(deplete the open files in the host, then recover), monit can not work normally when the config file is as follows:

check process kubelet matching "/usr/local/bin/kubelet"
    group kubelet
    start program = "/var/paas/monit/jobs/bin/kubelet_ctl start"
    stop program = "/var/paas/monit/jobs/bin/kubelet_ctl stop"
    if does not exist then restart
    **if failed port 10248 protocol HTTP**
         request /healthz
        with timeout 30 seconds
        for 4 times within 5 cycles
        then restart

errors:

[CST Apr 10 14:36:45] error    : Cannot translate 'localhost' to IP address -- Success
[CST Apr 10 14:36:45] error    : 'kubelet' failed protocol test [HTTP] at    [localhost]:10248/healthz [TCP/IP] -- Cannot resolve [localhost]:10248

[Tildeslash]

Please can you provide output of the following command?:

host localhost

When you don't specify the hostname in the connection test, monit adds a default value ("localhost"). It seems that in your case it doesn't resolve (which is strange, but possible). You can most probably fix the problem by setting the host explicitly using the "host <name | ipaddress>" option, example:

if failed host myhost.com port 10248 protocol HTTP ...

[wangbo]

tildeslash, thanks for your reply.

host localhost output is: -bash: host: command not found

and yes, i know if added the specific host it will work, but i just want to know the root case, any other suggestion? maybe this is a bug of monit.

[Tildeslash]

as mentioned, it seems that your system isn't able to resolve "localhost" ... it depends on your resolver configuration, not monit

[wangbo]

but if i call 'curl localhost:10248' in the host, it can work.

[Tildeslash]

Please check your name resolver configuration and make sure it resolves "localhost". Monit uses just standard system API to resolve the hostname.

[Massimo Sala]

wangbo, I suggest youto run these two command and upload here their outputs:

strace -f -e trace=network ping localhost

strace -f -e trace=network curl localhost:10248

They execute a ping and a curl on your localhost, logging al the operations. So we can see how localhost is resolved.