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Re: rogue process maxing cpu and unresponsive to signals

From: Decibel! <decibel(at)decibel(dot)org>
To: Jon Jensen <jon(at)jenseng(dot)com>
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: rogue process maxing cpu and unresponsive to signals
Date: 2007-08-16 05:03:21
Message-ID: (view raw or whole thread)
Lists: pgsql-novice
On Aug 15, 2007, at 9:27 PM, Jon Jensen wrote:
> I've got a simple select query that runs every 10 minutes in order  
> to update data in some external rrds (it lets us make pretty graphs  
> and so forth). This has been working fine for months on end, when  
> suddenly yesterday the badness happen. For some reason, this same  
> query that normally takes a couple seconds has now been stuck  
> running for over 24 hours, maxing the CPU and generally slowing  
> other queries down.
> The external script that initiates the query has been restarted,  
> and netstat no longer shows that connection. All subsequent calls  
> of the same query are quick as usual, but the renegade process  
> lingers on, unresponsive to signals. Some of the things I've tried  
> so far (unsuccessfully):
> 1. I've tried killing the process using kill from the command-line  
> (INT, TERM and HUP), as well as using pg_cancel_backend() via psql.
> 2. I've tried attaching gdb to the renegade process to see what  
> it's doing, but that hangs, forcing me to kill gdb (no problems  
> attaching to other postgres processes however).
> Any other ideas? I'd like to avoid doing a kill -9 if at all  
> possible. The machine is debian (sarge) running postgres 8.1.

There's a lot of parts of the code that don't check for signals,  
because normally they don't run for any real length of time... until  
they do. :) The factorial calculation is an example that was recently  
fixed. So it's possible that something in your query is in that same  
condition. You may be stuck with a kill -9, but it would be good to  
identify what part of the code is hung up so we can determine if it  
makes sense to add signal handling.
Decibel!, aka Jim Nasby                        decibel(at)decibel(dot)org
EnterpriseDB      512.569.9461 (cell)

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