Re: [monit] Resetting Checksums

[Martin Pala]

On Aug 28, 2008, at 4:43 AM, Art Age Software wrote:

> Hi,
>
> A couple monit questions:
>
> 1. Let's say I have monit monitoring the checksum of a file. I then
> make a change to the file which invalidates the checksum. What is the
> recommended way to tell monit to regenerate the checksum so that it
> does not alert and unmonitor the file, but causing the least impact.
> So far, the only thing that has worked for me has been to kill and
> restart monit itself.

This is simple - just use the "if changed checksum" statement:

--8<--
check file myfile with path /tmp/aaa
    if changed checksum then alert
--8<--

The "if changed checksum" reset the checksum and it check with the new  
value next cycle already.


> 2. When I restart monit, any "mode manual" services that were
> monitored become unmonitored after restart. Is there any way to
> restart monit and have it resume monitoring all the services it had
> been monitoring prior to restarting, including "mode manual" services?


The manual mode was planned for cluster - if the node is stopped, the  
services will be started on the other node (by heartbeat for example).  
Then if the original node is booted again, it's not good to start the  
same services on the same node, since they will be running twice (for  
example trying to get the cluster active/passive shared filesystem).

Monit stores the services state however for the unlikely event that  
monit will crash. If monit is started after such accident, it recovers  
to the state before the crash (including monitoring state of manual  
mode services). As workaround - if you are sure that you want to  
restart monit and keep the services state - you can kill monit using  
SIGKILL (pkill -9 monit). This way monit will be terminated uncleanly  
and will use the state self-healing on start - recover the original  
state.

We could also change the manual mode behavior to be persistent across  
restarts - it may make sense, i.e. if it was monitored before monit  
stop, enable monitoring after monit start again). The cluster  
framework should thus unmonitor the manual mode services if it is  
going to stop monit (or whole node) due to service failover.

Martin