[logback-dev] [JIRA] Commented: (LBCORE-220) DBAppender.java performance improvement

[Greg Thomas (JIRA)]

    [ http://jira.qos.ch/browse/LBCORE-220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12238#action_12238 ] 

Greg Thomas commented on LBCORE-220:
------------------------------------

I should have added at the time, I've submitted pull request 29 @ https://github.com/ceki/logback/pull/29 with a fix for this.

> DBAppender.java performance improvement
> ---------------------------------------
>
>                 Key: LBCORE-220
>                 URL: http://jira.qos.ch/browse/LBCORE-220
>             Project: logback-core
>          Issue Type: Bug
>          Components: Other
>    Affects Versions: 0.9.29
>            Reporter: Greg Thomas
>            Assignee: Logback dev list
>
> We're seeing a distinct lack of performance with the DBAppender. 
> Although it works fine in a single threaded environment, in a multi-threaded environment it slows down considerably. We've done some investigation, and narrowed it down to the pair of synchronized calls to subAppend() and selectEventId() (lines 107->110).
> I've had a look at this, and can see no reason for these to be synchronized;
> If using the JDBC3 getGeneratedKeys() method then as this applies to the thread specific statement there is no need to be synchronized.
> All the "Dialect" based calls are also connection specific; in detail;
> H2, HSQLDB and MySQL all call a database function, which is connection specific.
> MsSQL and Sybase both select a connection specific variable.
> Oracle and PostgreSQL both select the currval from a sequence, which again is connection specific.
> Having removed the synchronisation, we're seeing vastly improved logging throughput in our application.
> So to summarise; there is unnecessary synchronisation in the DBAppender that slows down multi-threaded applications; removing that synchronisation will improve performance in multi-threaded applications with no side affects.

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