Daemonizing Logic Error

[Andreas Ericsson]

Devin Bayer wrote:
> Hello:
> 
> We faced an issue when nagios silently failed to fork.  Since it's  
> part of  our startup scripts, this delayed the rest of the daemons  
> until nagios exited.

While it's bad that Nagios fails to daemonize OR die properly, your
startup-script parser really shouldn't hang indefinitely when it
encounters a start-script that doesn't return. I believe this should
be bug-reported to your distribution-vendor separately.

>  For this reason nagios should take care, that if  
> it doesn't daemonize correctly, it should die.  We are using nagios  
> 3.0.5, but I see the bug still exists in the trunk.  Here is our  
> nagios.log showing the problem:
> 
> [1242115575] Nagios 3.0.5 starting... (PID=773)
> [1242115575] Local time is Tue May 12 11:06:15 EEST 2009
> [1242115575] LOG VERSION: 2.0
> [1242115575] Finished daemonizing... (New PID=773)
> 

Right. This is indeed odd.

> Notice the "New PID" equals the old PID. I think this is the problem  
> code, from base/utils.c:
> 
> 2036 : 	   /* check for SIGHUP */
> 2037 : 	   if(val==1 && (pid=(pid_t)pidno)==getpid()){
> 2038 : 	    	close(lockfile);
> 2039 : 	   	return OK;
> 2040 : 	    	}
> 
> If nagios is started at boot time, it's somewhat likely it will have  
> about the same PID on the next boot.  So if the lockfile isn't cleaned  
> for some reason, then nagios will start, read the lockfile, and not  
> fork.
>     	
> 2042 : 	   /* exit on errors... */
> 2043 : 	   if((pid=fork())<0)
> 2044 : 	    	return(ERROR);
> 
> This looks like another bug.  If fork fails, we return ERROR, but the  
> return code is just silently ignored.
> 

Hmm. I'll look into this and see what may be done. Thanks for the report.

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

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