multhithreading issue using versions:set

[geirwr]

I am doing a versions:set but see some strange behaviour. Looks like it is a matter of non-threadsafe code. I have been testing on linux and windows, maven 3.3.9 and 3.3.1, same behavior.
Increasing number of parallel threads gives issue.

Workaround is to limit the number of parallel threads.

This issue surfaced using jenkins buildserver, and was easy to reproduce locally.

1. mvn versions:set -DnewVersion=1.0-SNAPSHOT (working)
2. mvn -X versions:set -DnewVersion=1.0-SNAPSHOT (working)
3. mvn -T1 versions:set -DnewVersion=1.0-SNAPSHOT (working)
4. mvn -T1 -e versions:set -DnewVersion=1.0-SNAPSHOT (working)
5. mvn -T1 -X versions:set -DnewVersion=1.0-SNAPSHOT (working on linux, fails on windows)
6. mvn -T2 versions:set -DnewVersion=1.0-SNAPSHOT (working)
7. mvn -T3 versions:set -DnewVersion=1.0-SNAPSHOT (working/fails, 50/50)
8. mvn -T4 versions:set -DnewVersion=1.0-SNAPSHOT (fails 100%)

[ERROR] java.util.concurrent.ExecutionException: java.lang.NullPointerException
java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.NullPointerException
at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder.multiThreadedProjectTaskSegmentBuild(MultiThreadedBuilder.java:174)
at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder.build(MultiThreadedBuilder.java:91)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:862)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder.multiThreadedProjectTaskSegmentBuild(MultiThreadedBuilder.java:166)
... 16 more
Caused by: java.lang.NullPointerException
at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call(MultiThreadedBuilder.java:189)
at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call(MultiThreadedBuilder.java:185)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

[khmarbaise]

At the moment the versions-maven-plugin supports also Maven 2 which does not know anything about -T... furthermore there is some code in there which is not thread safe...so we need to lift up the whole plugin to Maven 3+ only...that might solve the problem...but this is not a simple task...so please be patient.

[geirwr]

We have a workaround, so we have the patience.
looking forward to a version lifted to Maven 3...

[khmarbaise]

So after deeper investigation this is an regression of maven-core. Using Maven 3.0.5 it works without any issue starting with Maven 3.1.1 etc. it will fail with the NPE already created an issue for maven-core and already testing a fix for this....
In other words my previous assumption was wrong.

[khmarbaise]

The promised fix will be part of maven-3.5.0-alpha-2

[khmarbaise]

Sorry the fix is part for maven-3.5.0-beta-1 instead...which has been released...

[khmarbaise]

The issue has been fixed with Maven 3.5.0-beta-1 so I close this issue.

[geirwr]

thanks,
sorry for blaming versions-maven-plugin, as it turned out to be a maven-core issue.
good thing it is fixed!

[khmarbaise]

No problem..I wasn't sure at the beginning if it is versions-maven-plugin issue but later I realized it was a maven-core issue...