[MNG-6105] properties.internal.SystemProperties.addSystemProperties() is not really thread-safe

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.3.9
• Fix Version/s: 3.5.0-alpha-1, 3.5.0
• Component/s: Core

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"

• Assignee: Guillaume Boué
• Reporter: Falko Modler
• Created: 13/Oct/16 16:42
• Updated: 28/Mar/20 15:00
• Resolved: 28/Jan/17 13:16

Description

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:

[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

There seems to be concurrent system property removal while properties.internal.SystemProperties is iterating over the previously calculated property keys:

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 ) );
        }
}

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())

Issue Links

• is related to: MNG-5670 ConcurrentModificationException during DefaultMaven.newRepositorySession
• supercedes: MNG-6053 Unsafe System Properties copy in MavenRepositorySystemUtils, causing NPEs
• mentioned in: Page Loading...