Failing build during Maven MultiModule Parallel build due to absence of Reactor Project Output directory.

[pschhikara88]

Maven Module Setup

• RootModule
  • ReactorModule1
    • Module11
    • Module12
    • Module13
    • Module14
  • Module2

Run Command

mvn -T 1C clean install
mvn -T 1C -P scoverage scoverage:test

Error

Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-cli of goal org.scoverage:scoverage-maven-plugin:2.1.0:test failed.
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:133)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2 (MojoExecutor.java:328)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:316)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:174)
    at org.apache.maven.lifecycle.internal.MojoExecutor.access$000 (MojoExecutor.java:75)
    at org.apache.maven.lifecycle.internal.MojoExecutor$1.run (MojoExecutor.java:162)
    at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute (DefaultMojosExecutionStrategy.java:39)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:159)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:105)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:193)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:180)
    at java.util.concurrent.FutureTask.run (FutureTask.java:264)
    at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:539)
    at java.util.concurrent.FutureTask.run (FutureTask.java:264)
    at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1136)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:635)
    at java.lang.Thread.run (Thread.java:833)
Caused by: java.lang.NullPointerException
    at java.util.concurrent.ConcurrentHashMap.putVal (ConcurrentHashMap.java:1011)
    at java.util.concurrent.ConcurrentHashMap.put (ConcurrentHashMap.java:1006)
    at java.util.Properties.put (Properties.java:1301)
    at org.scoverage.plugin.SCoverageForkedLifecycleConfigurator.afterForkedLifecycleExit (SCoverageForkedLifecycleConfigurator.java:143)
    at org.scoverage.plugin.SCoverageIntegrationTestMojo.execute (SCoverageIntegrationTestMojo.java:87)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:126)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2 (MojoExecutor.java:328)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:316)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:174)
    at org.apache.maven.lifecycle.internal.MojoExecutor.access$000 (MojoExecutor.java:75)
    at org.apache.maven.lifecycle.internal.MojoExecutor$1.run (MojoExecutor.java:162)
    at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute (DefaultMojosExecutionStrategy.java:39)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:159)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:105)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:193)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:180)

Temporary Solution

**I got this error because my reactor project pom.xml is like this

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.ebay.mad.pl</groupId>
        <artifactId>RootModule</artifactId>
        <version>8.1</version>
    </parent>

    <artifactId>ReactorModule1</artifactId>
    <packaging>pom</packaging>
    <modules>
        <module>Module11</module>
        <module>Module12</module>
        <module>Module13</module>
        <module>Module14</module>
    </modules>
</project>

If you see here, we are not having any src folder in reactor project and not having maven-jar-plugin or any plugin which can create output directory. thats why it is giving NPE at SCoverageForkedLifecycleConfigurator.afterForkedLifecycleExit (SCoverageForkedLifecycleConfigurator.java:143)
https://github.com/scoverage/scoverage-maven-plugin/blob/main/src/main/java/org/scoverage/plugin/SCoverageForkedLifecycleConfigurator.java#L143

String originalOutputDirectory = (String) reactorProject.getProperties().remove( PROP_ORIG_OUTPUT_DIRECTORY );
forkedOutputDirectory = reactorProject.getBuild().getOutputDirectory();
  
reactorProject.getProperties().put( PROP_FORKED_OUTPUT_DIRECTORY, forkedOutputDirectory );
reactorProject.getBuild().setOutputDirectory( originalOutputDirectory );

**Solution
Add this in your ReactorModule1

<build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>test-jar</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

Permanent Solution

As reactor project output directory could be empty depends on its POM.
We are getting null as forkedOutputDirectory = reactorProject.getBuild().getOutputDirectory(); and when we are putting null in concurrentHashMap, it is giving NPE
reactorProject.getProperties().put( PROP_FORKED_OUTPUT_DIRECTORY, forkedOutputDirectory );

we could resolved it by putting it only when forkedOutputDirectory is not null.

if(forkedOutputDirectory!=null)
   reactorProject.getProperties().put( PROP_FORKED_OUTPUT_DIRECTORY, forkedOutputDirectory )

[jozic]

Hey, thanks for reporting. Our README mentions that multi threading is not supported

The plugin is not thread-safe, so it should not be used in multi-threaded builds.

But please feel free to send a PR with the fix and an integration test.

[pschhikara88]

@jozic thanks for reply. Yes in readme file, it is mentioned that this plugin is not thread safe. But when i was going through this link, it is mentioned that scoverage:test goal is thread safe and supports parallel build.
reference link : https://scoverage.github.io/scoverage-maven-plugin/2.1.0/test-mojo.html

Please let me know if my understanding is not correct. I am trying to use scoverage:test goal in parallel mode.

[jozic]

It could be that this doc is obsolete, I need to check the history and probably fix the doc until the main issue is fixed. But overall I believe it's not thread-safe.