[Backgroundrb-devel] trouble stopping backgroundrb

John O'Shea joshea at nooked.com
Wed Sep 17 12:35:37 EDT 2008

    Glad you raised this, I've been spending some time trying to 
diagnose this exact same problem. 
    The exception handling code in the "when 'stop'" block (in 
script/backgroundrb) could definitely could be improved somewhat
- check that the process with 'pid' exists before trying to kill it
- rescue permission exceptions (Errno::EPERM)
- only delete the pid file if the process pid does not still exist (in 
ensure block)
- be a little more verbose to stdout/stderr

While we are on the subject of shutdown, - when the backgroundrb process 
gets a HUP signal does it wait for existing workers to complete any work 
methods that are executing or is the 'Process.kill('-TERM', pgid)' call 
intended to make the OS handle this? 

We use capistrano to deploy our application (stopping and restarting 
backgroundrb after the rails app has been updated).  It would be great 
if we could have more predictability regarding shutting down 
backgroundrb (i.e. have the backgroundrb disable the reactor loop in 
idle workers and wait for all active workers to finish methods, then 


Jonathan Wallace wrote:
> Hi Ryan,
> I recently ran into the same issue where the backgroundrb process
> would not respond to ./script/backgroundrb stop command.  The pid file
> was being deleted but the actual process was not being killed.  I'm
> running packet 0.1.12 on gentoo.
> I'm not exactly sure what conditions put backgroundrb into such a
> state but I've decided to modify the script/backgroundrb to behave a
> little differently.
> My hypothesis is that if one of the Process.kill method calls in
> script/backgroundrb raises an exception, the pid file is deleted even
> though the kill signal is never sent.  At this point, running starting
> and stopping backgroundrb never affects the original still running
> backgroundrb process.
> There are a couple of reasons that I believe an exception could be
> raised.  Either the Process.getpgid(pid), Process.kill('TERM', pid) or
> the PRocess.kill('-TERM', pgid) raise an exception or the effective
> uid of the user running script/backgroundrb stop does not have
> permission to kill those processes.
> To fix this, we've removed the Process.getpgid and the two
> Process.kill's that are sending the TERM signal.  Since we've
> architected our backgroundrb jobs to be persistent and idempotent (a
> db backed queue written before the feature appeared in bdrb), we'll
> just use the KILL signal.
> Thoughts?
> Thanks,
>  Jonathan
> On Tue, Sep 16, 2008 at 12:11 PM, Ryan Case <mrryancase at gmail.com> wrote:
>> Hi folks -
>> I'm having trouble getting backgroundrb to stop after one of the
>> packet_worker_r processes dies.
>> If backgroundrb is running properly,
>> "/path/to/application/script/backgroundrb stop" works fine, but often
>> one of the packet_worker_r processes dies, and the stop command no
>> longer works after that (it runs, but it does not stop the processes,
>> and so then start doesn't work).
>> The only thing that seems to work at that point is to manually kill
>> the processes that are still running, and then the start works, but
>> that is going to make restarting via monit a lot less clean.
>> Any ideas would be much appreciated!
>> I'm using github version of backgroundrb, and packet 0.1.13 running on ubuntu.
>> Thanks!
>> Ryan
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John O'Shea, CTO at Nooked
www: http://www.nooked.com/
cell: +353 87 992 9959
skype: joshea

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