Re: Working with daemontools

[Martin Pala]

Paul Diaconescu wrote:

> Hi, 
>
> I'm using daemontools to supervise qmail, fetchmail, spamassassin, proftpd,
> etc. I'd like to have some kind of function tests on these programs
> (daemontools just restarts processes). An example:
>
> * proftpd is running but doesn't answer to requests. Monit should restart it
> with svc 3 times, give up and send me an alert. 
>
> * If the process isn't running monit should not try to start it since supervise
> is already trying that. 
>  
I recommend to use monit for both tasks instead of deamontools (i see no 
advantage of such combination).

To meet your requirements monit must test whether the process *is 
running* AND *is not responding* => it is possible to use "check process 
... " statement to suite the first condition. You can then mangle your 
startup script to ignore the start+stop action in the case that monit's 
environment variable MONIT_EVENT which is handed over to service startup 
script doesn't contain event of your choice (in your case "connection" 
event) => restart will be skipped.

This way it will behave as you want to, but there will be allways race 
condition possibility. To make 100% reliability of such symbiosis 
interprocess communication (for example locking file) must be used to 
take care for the critical section. This will involve modifications of 
daemontools and monit - i think it is not good way and it is better to 
choose one of them as mentioned above.

> More complex: To test that the mail system is working - send a mail to a
> testaddress. Check that the mail arrived, delete it and send again. If it
> hasn't arrived restart the maildaemons.
>  
Such sort of test is useful, but it is not (yet) implemented in monit.

Cheers,
Martin