Re: [monit] Re: File check with execution of a script

[Martin Pala]

Hi,

when the service is to be restarted and depends on some other service,  
monit tries to make sure that the parent service is running. The  
problem is, that monit doesn't use it's own parent service check  
result, but tries to verify that the parent service is OK directly  
during the restart ... and this "real-time" check is very limited:

1.) if the parent service is process, it checks that the process is  
running (independent of process service check result) ... if it's not  
running, monit tries to start it before the child service is started  
and then starts the child service. If the parent process is running  
already, monit just tries to start he child service directly.

2.) if the parent service is any other type (file, directory,  
filesystem, ...) then monit doesn't verify whether it is running or  
not and just calls the start method of the parent service (which may  
cascade if the dependency chain is longer as in your case).


In your case there is dependency chain of three file services defined  
as MNT -> MNTDEP -> MNTDEPDEP, whereas MNTDEPDEP+MNTDEP (grandparent +  
parent) exists, MNT (child) doesn't exist.

The monit verbose mode (-v option) shows the actions sequence:

--8<--
bash# monit -vIc ../monit_files validate
...
'MNTDEPDEP' file existence check succeeded
'MNTDEPDEP' is a regular file
'MNTDEP' file existence check succeeded
'MNTDEP' is a regular file
'MNT' file doesn't exist
'MNT' trying to restart
Monitoring disabled -- service MNT
'MNT' stop: /etc/monit/monit.sh
'MNTDEPDEP' start: /etc/monit/monit_dep_dep.sh
'MNTDEP' start: /etc/monit/monit_dep.sh
'MNT' start: /etc/monit/monit.sh
Monitoring enabled -- service MNT
--8<--


=> the behavior is given by current monit limitation. We plan to  
improve the dependency behavior and use the result of the full service  
check in the action chain, which will solve your problem.

The workaround could be to modify your scripts this way ... for  
example monit_dep.sh:
--8<--
#!/bin/bash

#
# WORKAROUND FOR MONIT DEPENDENCY ACTION CHAIN
#
if test -f /etc/monit/monit_dep.txt; then exit 0; fi

case $1 in
    start)
            touch /etc/monit/monit_dep.txt
            echo "asdfasdfasdfasdf" > /etc/monit/monit_dep.txt
            echo "monit start" >> /etc/monit/hier.txt
            ;;
    stop)
            echo "monit stop" >> /etc/monit/hier.txt
            ;;
esac
--8<--



Thanks,
Martin



On Sep 25, 2008, at 4:00 PM, Julian Thomé wrote:

> Sorry, i made an error in the last email
>
> the files monit_dep_dep.txt and monit_dep.txt exist and the file  
> monit.txt doesnt exist.
>
> Julian Thomé
>
>
>                 
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