[ http://issues.apache.org/jira/browse/VELOCITY-193?page=all ]
Nathan Bubna resolved VELOCITY-193:
-----------------------------------
Resolution: Fixed
This bug has been fixed in the 1.5-dev version, just like it says. Do not
reopen this unless you are using 1.5 and still have the problem.
> Memory/logger leak with multiple VelocityEngine instances
> ---------------------------------------------------------
>
> Key: VELOCITY-193
> URL: http://issues.apache.org/jira/browse/VELOCITY-193
> Project: Velocity
> Type: Bug
> Components: Source
> Versions: 1.3.1
> Environment: Operating System: All
> Platform: Macintosh
> Reporter: Ian Beatty
> Priority: Critical
> Fix For: 1.5
> Attachments: VelocityBugIsolator.tgz
>
> When creating and then releasing to garbage collection multiple
> VelocityEngine instances, the
> instances are apparently not closing out or otherwise letting go of their
> logger instances. As a
> result, code that needs to create and destroy several VelocityEngine
> instances will eventually choke
> and die. This happens with either Avalon Logkit or Log4j, although the exact
> nature of the choking
> differs. This test program isolates the problem:
> import org.apache.velocity.app.VelocityEngine;
> public class IsolateVelocityBug {
> static public void main( String[] args ) {
> int repCount = Integer.parseInt( args[0] );
> for( int i = 0; i < repCount; i++ ) {
> System.out.println( "Test repetition " + i + "..." );
> try {
> final VelocityEngine velocityEngine = new
> VelocityEngine();
> velocityEngine.init();
> } catch( Exception e ) {
> throw new Error( e );
> }
> }
> }
> }
> Run the program with an integer command-line argument specifying the number
> of times to cycle
> through the loop, and make sure velocity-1.3.1.jar, commons-collections.jar,
> and either an Avalon
> Logkit or Log4j JAR are on your classpath. (I tested with logkit-1.0.1.jar
> and log4j-1.1.3.jar.) What
> *should* happen is that the program completes its specified number of loops,
> doing nothing but
> writing "Test repetition" over and over with an incrementing number. What
> *does* happen, at least
> on my machine, depends on which logging package is provided for Velocity.
> Using Avalon Logkit 1.0.1, the program runs fine for 252 iterations; on the
> 253nd, it aborts with
> the following message:
> "PANIC : Error configuring AvalonLogSystem :
> java.io.FileNotFoundException: /Users/ibeatty/
> Development/javaDev/VelocityBugIsolator/velocity.log (Too many open files)"
> Using Log4j 1.1.3, the program runs fine for only one iteration; on the
> second and any subsequent
> iterations, it continues but prints out a whole mess of
> "log4j:ERROR Attempted to append to closed appender named [null].
> log4j:WARN Not allowed to write to a closed appender."
> That happens for as long as I care to let it run (95 iterations, with
> something over 800 lines of
> such errors per iteration by the end).
> To me, it sure looks like Velocity is leaving dangling loggers behind as
> VelocityEngine instances
> are created and discarded, and that the two logging systems respond
> differently to this but both
> have problems.
> Why, might you ask, should anyone care about making many VelocityEngine
> instances? I ran into it
> when developing a major web app using JUnit to build comprehensive test
> suites. To run
> independently, every test has to start from scratch, which means getting its
> own VelocityEngine.
> Many tests means many instances, and the logging problem kicks in. Running
> JUnit test suites
> within Intellij IDEA and using Log4j, the ERROR/WARN messages were more than
> a nuicanse;
> eventually, I'd start getting out-of-memory errors, too. These went away when
> I changed the tests
> to use a shared VelocityEngine instance (which caused its own set of
> problems).
> Using binary download of Velocity 1.3.1, which claims to have been created on
> 2003-04-01.
> I find it hard to believe nobody else has tripped over this before, so maybe
> it's sensitive to the OS
> or something. It happened whether I compiled the test code with Javac or
> Jikes. Using Java
> 1.4.1_01.
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