execute Error while generating diff
Asked by CM Team:

I keep seeing this showing up in my log...

2013-06-28 00:39:26,557 WARN \[http-8090-10\] \[confluence.pages.actions.AbstractDiffPagesAction\] execute Error while generating diff: (page: DEVINT7 Deployment

s v.73 (13893866) vs page: DEVINT7 Deployments v.74 (13893890))

-- url: /pages/diffpagesbyversion.action \| page: 10846216 \| userName: anonymous \| action: diffpagesbyversion

Ill see that about 3 times in a row several different times through the night....almost never during the day when our instance is under load. Almost everytime after i see this error i see this...

2013-06-28 00:42:58,224 WARN \[Timer-0\] \[mchange.v2.async.ThreadPoolAsynchronousRunner\] run com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector

@65dd7810 -- APPARENT DEADLOCK!!! Complete Status:

Managed Threads: 3

Active Threads: 3

Active Tasks:

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@74afeb0e (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@49711ffb (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@21eabd68 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)

Pending Tasks:

com.mchange.v2.resourcepool.BasicResourcePool$1RefurbishCheckinResourceTask@3a39083d

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@764bfaa7  
Anyone have any ideas about this? We keep running out of heap space over night and its causing all kinds of headaches here. Thanks


Answers:
author: CM Team
body: We figured it out...Google appliance was continually hitting our Confluence server trying to crawl through it. We added in a robots.txt file to stop it and that fixed this error.


author: CM Team
body: We figured it out...Google appliance was continually hitting our Confluence server trying to crawl through it. We added in a robots.txt file to stop it and that fixed this error.


author: JohnA
body: Hi Seth,

From the look of the error I think your Confluence is actually running out of resources because this is usually what that deadlocking error suggests. However, as you say it is at night and the server ins't under load at the time I suspect it's the scheduled XML backup running and failing that you are seeing, (it's a very resource hungry process!). So, what I would suggest is ensuring the daily "Backup Confluence" job is disabled, (instructions [here](https://confluence.atlassian.com/display/DOC/Scheduled+Jobs)), and then ensure that you are implementing a proper production backup strategy by following these instructions: <https://confluence.atlassian.com/display/DOC/Production+Backup+Strategy>

All the best,  
John


author: hsuhailah
body: This can be hard to diagnose because the message does not necessarily mean there is a deadlock. The code will output an apparent deadlock message when it attempts to grab a new database connection and there is none available. It can also happen if your instance is running out of memory and generating page difference is quite a memory expensive task.

Perhaps you can try to [increase the available memory](https://confluence.atlassian.com/display/CONFKB/How+to+Fix+Out+of+Memory+Errors+by+Increasing+Available+Memory) and see if that would help.


Tags: confluence-administration