Concurrency issue while using <xsl:key> Element with shared template object
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Key: XALANJ-2522
URL: https://issues.apache.org/jira/browse/XALANJ-2522
Project: XalanJ2
Issue Type: Bug
Security Level: No security risk; visible to anyone (Ordinary problems in
Xalan projects. Anybody can view the issue.)
Components: Xalan
Affects Versions: 2.7.1
Reporter: Michal Majcherski
There is concurrency problem while using <xsl:key> Element with shared template
object.
org.apache.xalan.templates.StylesheetRoot.m_keyDecls field which is shared for
all transformations of the same compiled XSL (held in impl. of
javax.xml.transform.Templates object) is implemented as java.util.Vector (which
is synchronized) what results in large synchronization times.
This has large impact on concurrent XSL transformation process with shared
compiled XSLs.
I run through lots of own tests of this issue and I saw that:
- transformation times were greatly increased, f.ex. from ~168ms even to
57684ms (!)
- threads that run long spent most of the time in Monitor state
(synchronization locks)
- CPU and memory were NOT greatly consumed (this is very important condition to
run mentioned tests)
I made an attempt to fix this issue by cloning m_keyDecls object on
getKeysComposed() method:
org.apache.xalan.templates.StylesheetRoot.java
public Vector getKeysComposed()
{
- return m_keyDecls;
+ return (Vector) m_keyDecls.clone();
}
I'm not very familiar with Xalan code so I'm not sure if this was the best
place to make a change, but this modification resulted in huge performance hit
- see attached full results.
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