Re: Unable to exec external script

[Martin Pala]

Thanks for the input :)

The problem is in the "if changed pid ..." statement usage. It comes 
true only if the monitored process PID changed without monit control - 
during the sleep between the monitoring cycles. If then monit wakes up 
and detects that the PID of the process is different since the last 
cycle, then it evaluates the "if changed pid ..." action.

In your case the process failed at all (didn't exist), thus monit 
performed the restart action. The PID will change of course, but this 
change is expected by monit, because monit drives the restart.

The "if changed pid ..." statement description (excerpt from monit manual):

--8<--
This test is useful to detect possible process restarts which has 
occurred in the timeframe between two monit testing cycles. In the case 
that the restart was fast and the process provides expected service 
(i.e. all tests passed) you will be notified that the process was replaced.

For example sshd daemon can restart very quickly, thus if someone 
changes its configuration and do sshd restart outside of monit control, 
you will be notified that the process was replaced by new instance (or 
you can optionaly do some other action such as preventively stop sshd).

Another example is MySQL Cluster which has its own watchdog with process 
restart ability. You can use monit for redundant monitoring. Monit will 
just send alert in the case that the MySQL cluster restarted the node 
quickly.
--8<--

Martin


Dragan Zubac wrote:
> Hello
>
> Sure thing,here's the whole test setup:
>
> a. application to be monitored is called program.sh (basically every 
> second echo date command output to some /tmp/program.out file),the 
> program itself does not set up it's own pid
>
> b. start up script is called start.sh with start/stop switch,and it's 
> also a wrapper around application handling pid's and stuff like that
>
> In attachment is also :
>
> a. monit.log file,during a couple of cycles where I changed exec action 
> directive in monitrc command to explicitly use bash shell - filename 
> monit.log
> b. first monitrc file (before modification) - filename monitrc~
> c. second monitrc file (after modification) - filename monitrc
> d. script to be execute on event (changed pid in this case) which can 
> accept optional parameter
>     - filename test.sh
> e. monit -vI output file - filename monit.out
>
> During test I monitored /tmp/helo.out which is a file where goes output 
> of external script to be execured each time a pid is changed of 
> monitored application (program.sh),and there was nothing indicating that 
> monit even tried to execute test.sh script on changed pid event.
> I even tried to strace monit's child process after monit startup,but in 
> logs there was no presence of test.sh.
> The system I'm using is SuSE v9.3,default installation.
>
> Am I missing something or some other mistake I make ?
>
> Sincerely
>
> Dragan
>
>
>
>
>
> On 12/6/06, *Martin Pala* <address@hidden 
> <mailto:address@hidden>> wrote:
>
>     Hello,
>
>     can you describe the configuration and situation where you expect the
>     exec to happen in more detail? Also the log output from monit verbose
>     mode (-v option) could be useful.
>
>     Thanks,
>     Martin
>
>     Dragan Zubac wrote:
>      > Hello
>      >
>      > I'm trying to configure monit software ver. 4.8.1,and was unable to
>      > configure moinit to exec some external script on certain events.Tried
>      > the following scenarios:
>      >
>      > a. exec "/path/to/script"
>      > b. exec "/bin/bash -c '/path/to/script' "
>      >
>      > also tried to strace monit while active,and turning on the debuging
>      > while active,but couldn't find any attempt to start this script ?
>      >
>      > Any clue ?
>      >
>      > Sincerely
>      >
>      > Dragan