HADOOP-13428. Fixed hadoop-common build files to generate jdiff by working around a jdiff-bug. Contributed by Wangda Tan.

hadoop-common-project/hadoop-common/dev-support/jdiff-workaround.patch

@@ -0,0 +1,98 @@
+diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/MetricsSystem.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/MetricsSystem.java
+index a277abd..ed7c709 100644
+--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/MetricsSystem.java
++++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/MetricsSystem.java
+@@ -43,18 +43,6 @@
+   public abstract MetricsSystem init(String prefix);
+
+   /**
+-   * Register a metrics source
+-   * @param <T>   the actual type of the source object
+-   * @param source object to register
+-   * @param name  of the source. Must be unique or null (then extracted from
+-   *              the annotations of the source object.)
+-   * @param desc  the description of the source (or null. See above.)
+-   * @return the source object
+-   * @exception MetricsException
+-   */
+-  public abstract <T> T register(String name, String desc, T source);
+-
+-  /**
+    * Unregister a metrics source
+    * @param name of the source. This is the name you use to call register()
+    */
+@@ -77,18 +65,19 @@
+    */
+   @InterfaceAudience.Private
+   public abstract MetricsSource getSource(String name);
++
+
+   /**
+-   * Register a metrics sink
+-   * @param <T>   the type of the sink
+-   * @param sink  to register
+-   * @param name  of the sink. Must be unique.
+-   * @param desc  the description of the sink
+-   * @return the sink
++   * Register a metrics source
++   * @param <T>   the actual type of the source object
++   * @param source object to register
++   * @param name  of the source. Must be unique or null (then extracted from
++   *              the annotations of the source object.)
++   * @param desc  the description of the source (or null. See above.)
++   * @return the source object
+    * @exception MetricsException
+    */
+-  public abstract <T extends MetricsSink>
+-  T register(String name, String desc, T sink);
++  public abstract <T> T register(String name, String desc, T source);
+
+   /**
+    * Register a callback interface for JMX events
+diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSystemImpl.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSystemImpl.java
+index 6986edb..eeea81f 100644
+--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSystemImpl.java
++++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/impl/MetricsSystemImpl.java
+@@ -270,27 +270,6 @@ void registerSource(String name, String desc, MetricsSource source) {
+     LOG.debug("Registered source "+ name);
+   }
+
+-  @Override public synchronized <T extends MetricsSink>
+-  T register(final String name, final String description, final T sink) {
+-    LOG.debug(name +", "+ description);
+-    if (allSinks.containsKey(name)) {
+-      LOG.warn("Sink "+ name +" already exists!");
+-      return sink;
+-    }
+-    allSinks.put(name, sink);
+-    if (config != null) {
+-      registerSink(name, description, sink);
+-    }
+-    // We want to re-register the sink to pick up new config
+-    // when the metrics system restarts.
+-    register(name, new AbstractCallback() {
+-      @Override public void postStart() {
+-        register(name, description, sink);
+-      }
+-    });
+-    return sink;
+-  }
+-
+   synchronized void registerSink(String name, String desc, MetricsSink sink) {
+     checkNotNull(config, "config");
+     MetricsConfig conf = sinkConfigs.get(name);
+diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestGangliaMetrics.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestGangliaMetrics.java
+index c19d238..f8412f1 100644
+--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestGangliaMetrics.java
++++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestGangliaMetrics.java
+@@ -130,8 +130,8 @@ public void testTagsForPrefix() throws Exception {
+     GangliaMetricsTestHelper.setDatagramSocket(gsink31, mockds31);
+
+     // register the sinks
+-    ms.register("gsink30", "gsink30 desc", gsink30);
+-    ms.register("gsink31", "gsink31 desc", gsink31);
++    //ms.register("gsink30", "gsink30 desc", gsink30);
++    //ms.register("gsink31", "gsink31 desc", gsink31);
+     ms.publishMetricsNow(); // publish the metrics
+
+     ms.stop();

hadoop-common-project/hadoop-common/pom.xml

@@ -34,6 +34,7 @@
     <kdc.resource.dir>src/test/resources/kdc</kdc.resource.dir>
     <hadoop.component>common</hadoop.component>
     <is.hadoop.component>true</is.hadoop.component>
+    <is.hadoop.common.component>true</is.hadoop.common.component>
     <wsce.config.dir>../etc/hadoop</wsce.config.dir>
     <wsce.config.file>wsce-site.xml</wsce.config.file>
   </properties>
@@ -512,6 +513,7 @@
             <exclude>src/test/resources/test.har/_masterindex</exclude>
             <exclude>src/test/resources/test.har/part-0</exclude>
             <exclude>src/test/resources/javakeystoreprovider.password</exclude>
+            <exclude>dev-support/jdiff-workaround.patch</exclude>
           </excludes>
         </configuration>
       </plugin>

hadoop-project-dist/pom.xml

@@ -160,7 +160,7 @@
         <activeByDefault>false</activeByDefault>
       </activation>
       <properties>
-        <jdiff.stable.api>2.6.0</jdiff.stable.api>
+        <jdiff.stable.api>2.7.2</jdiff.stable.api>
         <jdiff.stability>-unstable</jdiff.stability>
         <!-- Commented out for HADOOP-11776 -->
         <!-- Uncomment param name="${jdiff.compatibility}" in javadoc doclet if compatibility is not empty -->
@@ -241,6 +241,26 @@
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-antrun-plugin</artifactId>
             <executions>
+
+              <!-- Pre site -->
+              <execution>
+                <id>pre-site</id>
+                <phase>prepare-package</phase>
+                <goals>
+                  <goal>run</goal>
+                </goals>
+                <configuration>
+                  <target if="is.hadoop.common.component">
+                    <!-- HADOOP-13428: This is for workaround issues of JDiff
+                         - https://sourceforge.net/p/javadiff/bugs/19/ -->
+                    <exec executable="patch" input="dev-support/jdiff-workaround.patch" dir="${basedir}">
+                        <arg value="-p3"/>
+                    </exec>
+                  </target>
+                </configuration>
+              </execution>
+
+
               <execution>
                 <id>site</id>
                 <phase>prepare-package</phase>
@@ -249,7 +269,6 @@
                 </goals>
                 <configuration>
                   <target if="is.hadoop.component">
-
                     <mkdir dir="${project.build.directory}/docs-src"/>
 
                     <!-- Docs -->
@@ -302,6 +321,25 @@
                   </target>
                 </configuration>
               </execution>
+
+              <!-- post site phase -->
+              <execution>
+                <id>post-site</id>
+                <phase>prepare-package</phase>
+                <goals>
+                  <goal>run</goal>
+                </goals>
+                <configuration>
+                  <target if="is.hadoop.common.component">
+                    <!-- HADOOP-13428: Revert temporary patch-->
+                    <exec executable="patch" input="dev-support/jdiff-workaround.patch" dir="${basedir}">
+                        <arg value="-p3"/>
+                        <arg value="-R"/>
+                    </exec>
+                  </target>
+                </configuration>
+              </execution>
+
             </executions>
           </plugin>
         </plugins>