[MNG-4738] DefaultArtifactResolver forks non-daemon threads

Submitted by: Benjamin Hanzelmann

git-svn-id: https://svn.apache.org/repos/asf/maven/maven-3/trunk@979028 13f79535-47bb-0310-9956-ffa450edef68

maven-compat/src/main/java/org/apache/maven/artifact/resolver/DefaultArtifactResolver.java

@@ -32,8 +32,10 @@ import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
 
 import org.apache.maven.artifact.Artifact;
 import org.apache.maven.artifact.factory.ArtifactFactory;
@@ -125,7 +127,7 @@ public class DefaultArtifactResolver
         else
         {
             executor =
-                new ThreadPoolExecutor( threads, threads, 3, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>() );
+                new ThreadPoolExecutor( threads, threads, 3, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(), new DaemonThreadCreator());
         }
     }
 
@@ -687,6 +689,26 @@ public class DefaultArtifactResolver
         resolve( artifact, remoteRepositories, localRepository, null );
     }
 
+    /**
+     * ThreadCreator for creating daemon threads with fixed ThreadGroup-name.
+     */
+    final static class DaemonThreadCreator
+        implements ThreadFactory
+    {
+        static final String THREADGROUP_NAME = "org.apache.maven.artifact.resolver.DefaultArtifactResolver";
+
+        final static ThreadGroup group = new ThreadGroup( THREADGROUP_NAME );
+
+        final static AtomicInteger threadNumber = new AtomicInteger( 1 );
+
+        public Thread newThread( Runnable r )
+        {
+            Thread newThread = new Thread( group, r, "resolver-" + threadNumber.getAndIncrement() );
+            newThread.setDaemon( true );
+            return newThread;
+        }
+    }
+
     private class ResolveTask
         implements Runnable
     {

maven-compat/src/test/java/org/apache/maven/artifact/resolver/DefaultArtifactResolverTest.java

@@ -1,10 +1,88 @@
 package org.apache.maven.artifact.resolver;
 
-import org.codehaus.plexus.PlexusTestCase;
+import java.util.Collections;
+
+import org.apache.maven.artifact.AbstractArtifactComponentTestCase;
+import org.apache.maven.artifact.Artifact;
+import org.apache.maven.artifact.resolver.DefaultArtifactResolver.DaemonThreadCreator;
 
 public class DefaultArtifactResolverTest
-    extends PlexusTestCase
+    extends AbstractArtifactComponentTestCase
 {
+    private DefaultArtifactResolver artifactResolver;
+
+    private Artifact projectArtifact;
+
+    @Override
+    protected void setUp()
+        throws Exception
+    {
+        super.setUp();
+
+        artifactResolver = (DefaultArtifactResolver) lookup( ArtifactResolver.class );
+
+        projectArtifact = createLocalArtifact( "project", "3.0" );
+    }
+
+    @Override
+    protected void tearDown()
+        throws Exception
+    {
+        artifactFactory = null;
+        projectArtifact = null;
+        super.tearDown();
+    }
+
+    @Override
+    protected String component()
+    {
+        return "resolver";
+    }
+
+    public void testMNG4738()
+        throws Exception
+    {
+        Artifact g = createLocalArtifact( "g", "1.0" );
+        createLocalArtifact( "h", "1.0" );
+        artifactResolver.resolveTransitively( Collections.singleton( g ), projectArtifact, remoteRepositories(),
+                                              localRepository(), null );
+
+        // we want to see all top-level thread groups
+        ThreadGroup tg = Thread.currentThread().getThreadGroup();
+        while ( !( tg.getParent() != null ) )
+        {
+            tg = tg.getParent();
+        }
+
+        ThreadGroup[] tgList = new ThreadGroup[tg.activeGroupCount()];
+        tg.enumerate( tgList );
+
+        boolean seen = false;
+
+        for ( int i = 0; i < tgList.length; i++ )
+        {
+            if ( !tgList[i].getName().equals( DaemonThreadCreator.THREADGROUP_NAME ) )
+            {
+                continue;
+            }
+
+            seen = true;
+
+            tg = tgList[i];
+            Thread[] ts = new Thread[tg.activeCount()];
+            tg.enumerate( ts );
+
+            for ( Thread active : ts )
+            {
+                String name = active.getName();
+                boolean daemon = active.isDaemon();
+                assertTrue( name + " is no daemon Thread.", daemon );
+            }
+
+        }
+
+        assertTrue( "Could not find ThreadGroup: " + DaemonThreadCreator.THREADGROUP_NAME, seen );
+    }
 
     public void testLookup()
         throws Exception