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https://issues.apache.org/jira/browse/MNG-6105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15578189#comment-15578189
]
Guillaume Boué commented on MNG-6105:
-------------------------------------
So the issue is about copying one Properties to another. Why would
synchronizing on the source property instance not be enough? I.e, following
code:
{code:java}
public static Properties copyProperties( Properties properties )
{
final Properties copyProperties = new Properties();
synchronized ( properties )
{
copyProperties.putAll( properties );
}
return copyProperties;
}
{code}
I ran all core-its with this (both on Windows 10 and Ubuntu 16.04) and didn't
have any issues. I also ran a build of {{maven-plugins-aggregator}} with {{-T
5}}. Since it synchronizes on the given properties, it makes sure no other
thread can remove a key or set a different value to a key during the iteration
in {{putAll}}. I also noticed this is what some [Oracle internal code
does|http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/8u40-b25/sun/management/Agent.java/#175]
([relevant
mail|http://mail.openjdk.java.net/pipermail/core-libs-dev/2012-April/009795.html]).
> properties.internal.SystemProperties.addSystemProperties() is not really
> thread-safe
> ------------------------------------------------------------------------------------
>
> Key: MNG-6105
> URL: https://issues.apache.org/jira/browse/MNG-6105
> Project: Maven
> Issue Type: Bug
> Components: core
> Affects Versions: 3.3.9
> Environment: Apache Maven 3.3.9
> (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-10T17:41:47+01:00)
> Maven home: /usr/maven/default
> Java version: 1.8.0_102, vendor: Oracle Corporation
> Java home: /usr/java/jdk1.8.0_102/jre
> Default locale: en_US, platform encoding: UTF-8
> OS name: "linux", version: "2.6.32-431.29.2.el6.x86_64", arch: "amd64",
> family: "unix"
> Reporter: Falko Modler
> Assignee: Guillaume Boué
>
> We got a rather large Maven project with a couble of modules that execute
> {{maven-assembly-plugin}}. Our build runs in parallel mode via {{-Tx}}.
> From time to time we are seeing following exception causing the respective
> build to fail:
> {noformat}
> [ERROR] Failed to execute goal
> org.apache.maven.plugins:maven-assembly-plugin:2.6:single (assembly-zip) on
> project some-module: Execution assembly-zip of goal
> org.apache.maven.plugins:maven-assembly-plugin:2.6:single failed.
> NullPointerException -> [Help 1]
> org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute
> goal org.apache.maven.plugins:maven-assembly-plugin:2.6:single (assembly-zip)
> on project some-module: Execution assembly-zip of goal
> org.apache.maven.plugins:maven-assembly-plugin:2.6:single failed.
> at
> org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
> at
> org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
> at
> org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
> at
> org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
> at
> org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call(MultiThreadedBuilder.java:185)
> at
> org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call(MultiThreadedBuilder.java:181)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266)
> at
> java.util.concurrent.Executors$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)
> Caused by: org.apache.maven.plugin.PluginExecutionException: Execution
> assembly-zip of goal
> org.apache.maven.plugins:maven-assembly-plugin:2.6:single failed.
> at
> org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145)
> at
> org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
> ... 11 more
> Caused by: java.lang.NullPointerException
> at java.util.Hashtable.put(Hashtable.java:459)
> at
> org.apache.maven.properties.internal.SystemProperties.addSystemProperties(SystemProperties.java:38)
> at
> org.apache.maven.project.artifact.MavenMetadataSource.getSystemProperties(MavenMetadataSource.java:756)
> at
> org.apache.maven.project.artifact.MavenMetadataSource.retrieveRelocatedProject(MavenMetadataSource.java:574)
> at
> org.apache.maven.project.artifact.MavenMetadataSource.retrieve(MavenMetadataSource.java:190)
> at
> org.apache.maven.repository.legacy.resolver.DefaultLegacyArtifactCollector.recurse(DefaultLegacyArtifactCollector.java:532)
> at
> org.apache.maven.repository.legacy.resolver.DefaultLegacyArtifactCollector.recurse(DefaultLegacyArtifactCollector.java:584)
> at
> org.apache.maven.repository.legacy.resolver.DefaultLegacyArtifactCollector.collect(DefaultLegacyArtifactCollector.java:144)
> at
> org.apache.maven.artifact.resolver.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:493)
> at
> org.apache.maven.artifact.resolver.DefaultArtifactResolver.resolveWithExceptions(DefaultArtifactResolver.java:348)
> at
> org.apache.maven.artifact.resolver.DefaultArtifactResolver.resolveTransitively(DefaultArtifactResolver.java:342)
> at
> org.apache.maven.artifact.resolver.DefaultArtifactResolver.resolveTransitively(DefaultArtifactResolver.java:321)
> at
> org.apache.maven.artifact.resolver.DefaultArtifactResolver.resolveTransitively(DefaultArtifactResolver.java:286)
> at
> org.apache.maven.plugin.assembly.artifact.DefaultDependencyResolver.resolveTransitively(DefaultDependencyResolver.java:253)
> at
> org.apache.maven.plugin.assembly.artifact.DefaultDependencyResolver.resolveDependencySets(DefaultDependencyResolver.java:169)
> at
> org.apache.maven.plugin.assembly.archive.phase.DependencySetAssemblyPhase.execute(DependencySetAssemblyPhase.java:94)
> at
> org.apache.maven.plugin.assembly.archive.DefaultAssemblyArchiver.createArchive(DefaultAssemblyArchiver.java:178)
> at
> org.apache.maven.plugin.assembly.mojos.AbstractAssemblyMojo.execute(AbstractAssemblyMojo.java:484)
> at
> org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
> ... 12 more
> [ERROR]
> [ERROR] Re-run Maven using the -X switch to enable full debug logging.
> [ERROR]
> [ERROR] For more information about the errors and possible solutions, please
> read the following articles:
> [ERROR] [Help 1]
> http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException
> {noformat}
> There seems to be concurrent system property removal while
> {{properties.internal.SystemProperties}} is iterating over the previously
> calculated property keys:
> {code:java|title=https://github.com/apache/maven/blob/maven-3.3.9/maven-core/src/main/java/org/apache/maven/properties/internal/SystemProperties.java}
> /**
> * Thread-safe System.properties copy implementation.
> *
> * @see "https://issues.apache.org/jira/browse/MNG-5670";
> */
> public static void addSystemProperties( Properties props )
> {
> for ( String key : System.getProperties().stringPropertyNames() )
> {
> props.put( key, System.getProperty( key ) );
> }
> }
> {code}
> {{System.getProperty( key )}} possibly yields a {{null}} value which
> {{Hashtable/Properties}} does not accept.
> *Possible solutions*:
> - refrain from adding {{null}} by explicitly checking for it
> - replace {{for}}-loop with {{props.addAll(System.getProperties().clone())}}
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