Re: Monit Can't Stop Apache

[Chris Lopeman]

Jan-Henrik Haukeland wrote:

> On Mar 1, 2005, at 0:03, Chris Lopeman wrote:
>
> > Actually I am using Apache 2.0.?. 
>
>
> I belive the prefork model is the default for apache 2.x also. Even 
> the threaded models forks of a few child processes which will act as 
> workers with a thread pool. The thing is, (as Martin said) if you do a 
> kill -9 on the main controlling httpd process, i.e. the one referenced 
> in the httpd.pid file monit will have problems managing apache. Before 
> I explain why, I should point out that killing the main apache process 
> with -9 is not smart and imply that you need to read up on how apache 
> works :-) The main apache process controls all of its child processes 
> and is also responsible for gracefully closing them down, which it 
> will do if you send the main process a TERM signal using e.g. kill 
> *without* -9. But if you murder the controller as you do with kill -9 
> it will die immediately and not get a chance to cleanup. The result is 
> that apache child processes will continue to run and answer on port 80 
> (or whatever), and that's the reason monit cannot start apache again 
> because a new apache instance cannot bind to port 80. See? And because 
> there are no controlling process you need to "manually" kill every 
> running child process before apache can start (and bind to port 80) 
> again. You can do this by e.g. using "killall -9 httpd" from the shell 
> to get rid of the stray httpd children.

Based on what you said above, I really think you are missing the point.  
The kill -9 is not something I would normally do.  It was not meant to 
be a clean way of exiting apache.  It is a simulation of something going 
wrong.  Just the type of thing that Monit is there to handle. 

> > However, I would assume the same  holds true.  What you have 
> > suggested is basically to create a custom script to clean up Apache 
> > if parts are still running.  But that seems kind of silly to do since 
> > "httpd restart" already does a great job of this.  You seem to be 
> > implying that there is something wrong with calling "httpd restart".
>
>
> What do you mean by calling "httpd restart"? If httpd is the apache 
> httpd program it does not take no "restart" argument. If it is a 
> script/program and it really does cleanup any stray httpd children 
> before starting apache why don't you simply use this in monit's 
> start-program statement? BTW afaik /etc/init.d/apache at least on my 
> Unix systems (FC2 and Mac OS X) will have problems starting apache 
> again if you kill the controlling process and have httpd children 
> floating around on the system.
>
> > Anyway I think I was too subtle.  My real questions more general.  
> > Should people setting up monit seriously consider using restart on 
> > each process instead of  start? 
>
>
> No
>
> > Or should monit trust the stop scripts more and just run them? 
>
>
> No
>
> > After all should not they be best at detecting if it is still running 
> > and if anything needs to be cleaned up.  Maybe the best of both 
> > worlds is to provided monit with a flag for each stop command that 
> > tells it to force the stop to run or not.
>
>
> IMHO the best would be to know how your daemon works and write or use 
> your start and stop program accordingly.
>
> --
> Jan-Henrik Haukeland
> Mobil +47 97141255
>
>
>
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