[VELOCITY-556] Another concurrency issue with macros

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.5
• Fix Version/s: 1.6
• Component/s: Engine
• Assignee: Unassigned
• Reporter: Dima Tkach
• Created: 20/Jun/07 22:02
• Updated: 24/Aug/07 05:08
• Resolved: 24/Aug/07 05:08

Description

The symptom is similar to
https://issues.apache.org/jira/browse/VELOCITY-514 and
https://issues.apache.org/jira/browse/VELOCITY-24

• the 'Null AST' errors show up in the logs under concurrency.
  The issue is different however. First, unlike those two, this one only happens when the macro caching is ON (at least, I was never able to reproduce it with the cache off), and second, the issue only appears when there is a macro call from inside a macro. Like this:
  #macro A() A #end
  #macro AB() #A()B#end

I have debugged this problem, and came up with this fix. I replaced Velocimacro.class file in velocity-1.5.jar with the one I compiled with my fix, and have been running it in production evironment for a while. It does indeed seem to have fixed the problem.
Please feel free to use this fix if you like it.

— org/apache/velocity/runtime/directive/VelocimacroProxy.orig 2007-06-08 19:21:19.000000000 -0400
+++ org/apache/velocity/runtime/directive/VelocimacroProxy.java 2007-06-08 19:22:10.000000000 -0400
@@ -164,11 +164,14 @@

if (nodeTree != null)
{
+ synchronized (this)
+ {
if ( !init )

{ nodeTree.init( context, rsvc); init = true; }

+ }

/*

• wrap the current context and add the VMProxyArg objects

– Dima