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From Dr James Smith <...@sanger.ac.uk>
Subject Re: Random segmentation fault
Date Sun, 06 Sep 2015 08:48:00 GMT
John,

Sometimes it's difficult to see what the error is because you can't see 
the request (doesn't get logged)

To get round this - add:

  * a transhandler which writes a tag (e.g. ST), the request and the PID
    to the error log
  * a cleanuphandler which does the same... with a different tag (e.g. FI)

you can then get a better idea of what is causing the error as the 
request that causes the seg-fault will have a ST just before the seg 
fault but no FI... you will also have a history of all the request 
handled by that PID (in case it is cumulative)

Sometime (about 12 years) ago we were having errors with apparently 
random requests (including static images) - doing this we discovered the 
request which died was the request after a request which talked to a 
particular Oracle database.

On the live site we just killed the child at the end of these 
requests... and then went back to diagnose the error...

James

On 03/09/2015 22:21, John Dunlap wrote:
> Ever since upgrading from Debian 7 - which shipped with Apache 2.2 - 
> to Debian 8 - which shipped with Apache 2.4 - my user base has been 
> reporting that their browsers randomly tell them "No data received". 
> To date, they have not been able to identify any kind of pattern which 
> triggers it. I've been sifting through the server logs looking for 
> problems and I'm seeing a lot of errors similar to the following:
> [Thu Sep 03 21:12:52.382357 2015] [core:notice] [pid 13199:tid 
> 140364918835072] AH00052: child pid 2088 exit signal Segmentation 
> fault (11)
> [Thu Sep 03 21:13:03.406215 2015] [core:notice] [pid 13199:tid 
> 140364918835072] AH00052: child pid 2121 exit signal Segmentation 
> fault (11)
> [Thu Sep 03 21:13:05.417909 2015] [core:notice] [pid 13199:tid 
> 140364918835072] AH00052: child pid 2165 exit signal Segmentation 
> fault (11)
> [Thu Sep 03 21:13:08.433829 2015] [core:notice] [pid 13199:tid 
> 140364918835072] AH00052: child pid 2232 exit signal Segmentation 
> fault (11)
> [Thu Sep 03 21:15:53.614351 2015] [core:notice] [pid 13199:tid 
> 140364918835072] AH00052: child pid 2264 exit signal Segmentation 
> fault (11)
> [Thu Sep 03 21:16:03.637236 2015] [core:notice] [pid 13199:tid 
> 140364918835072] AH00052: child pid 2539 exit signal Segmentation 
> fault (11)
>
>
> Can someone give me some tips on how to proceed with troubleshooting 
> this and, possibly, fixing it?
>
> -- 
> John Dunlap
> /CTO | Lariat/
> /
> /
> /*Direct:*/
> /john@lariat.co <mailto:john@lariat.co>/
> /
> *Customer Service:*/
> 877.268.6667
> support@lariat.co <mailto:support@lariat.co>




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