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Date: Fri, 23 Sep 2011 19:51:28 +0000 (UTC)
From: "Mamta A. Satoor (JIRA)" <jira@apache.org>
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Subject: [jira] [Reopened] (DERBY-5426) Improve the error raised by too much
 contention on a sequence/identity.
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     [ https://issues.apache.org/jira/browse/DERBY-5426?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mamta A. Satoor reopened DERBY-5426:
------------------------------------


I just wanted to see if we could have a standalone program to reproduce the sequence contention error. If that program works then may be we can add it to our junit suite. 

I am trying to work on a repo but what I wrote does not run into sequence contention.  I was hoping I could get some tips on how I could tune the program to make it run into problem(I understand it may not reproduce everytime). I will attach the program soon with instruction on how to run it and what parameters I have tried. Thanks

> Improve the error raised by too much contention on a sequence/identity.
> -----------------------------------------------------------------------
>
>                 Key: DERBY-5426
>                 URL: https://issues.apache.org/jira/browse/DERBY-5426
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.8.2.1, 10.9.0.0
>            Reporter: Rick Hillegas
>            Assignee: Rick Hillegas
>             Fix For: 10.8.2.2, 10.9.0.0
>
>         Attachments: derby-5426-01-aa-improveError.diff
>
>
> Currently, when there is too much contention on a sequence/identity, Derby raises an error saying so. There are two properties which the user can adjust in order to reduce the risk of this error:
> derby.locks.waitTimeout
> derby.language.sequence.preallocator
> It would be good to point the user at these knobs. The following change would improve this error reporting:
> 1) Raise a lock timeout SQLException
> 2) Chain a "too much contention" SQLException (X0Y84) to the lock timeout.
> 3) Make the "too much contention" exception suggest that the user adjust the properties mentioned above.
> To make the code easier to understand, the exception raising could replace the loop exit inside the following "if" block in SequenceUpdater.getCurrentValueAndAdvance():
>             if (
>                 (_lockTimeoutInMillis >= 0L) &&
>                 ( (System.currentTimeMillis() - startTime.longValue()) > _lockTimeoutInMillis )
>                 )
>             {
>                 break;
>             }
> This approach was recommended by the discussion on DERBY-5423.

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