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

Greg Thomas (JIRA) noreply-jira at qos.ch
Wed Sep 7 18:17:16 CEST 2011

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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