DBAppender.java performance improvement
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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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