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Re: Not the way I would hav dependents work


From: Jan-Henrik Haukeland
Subject: Re: Not the way I would hav dependents work
Date: Wed, 16 Feb 2005 13:05:34 +0100


On Feb 16, 2005, at 0:48, Chris Lopeman wrote:

SO I recently discovered that during a restart a dependent process will
restart at the same time as the parent process. Basically speaking the
parent start and in less than a second (I believe before the parent
script even completes), the dependent's start script is run.  If these
are being forked off it is even possible for the dependent script to
actually complete execution before the Parent has really started
execution.  Anyway, seems to me that dependent should mean dependent.
Monit should check or start dependent processes unless what they depend
on is all good (running and responding).  Instead Monit attempts to run
and monitor these processes, basically setting itself for failure and
errors.

You have a point here. Upon restart of a depend tree monit will do as you expect on shutdown, but maybe not on start up. Or rather the startup is debatable.

Assume this depend tree: A->B

Now on restart of A monit will first stop B and *wait* on B to stop *before* it will stop A. However on startup monit will simply fork of and start B and then A, *in sequence* but without waiting for B to actually start before A is started. In other words you _can_ get the behavior you describe above. Maybe we should change the startup sequence in monit to behave as on stop? I.e. that monit waits on B to start before it attempts to start A.

--
Jan-Henrik Haukeland
mobile +47 97141255





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