YARN-6627. Addendum patch for branch-2. (Sunil G via asuresh)

(cherry picked from commit 5cd92ed555cadf4897e4ab378fcc6691bfbd6bbe)

hadoop-assemblies/src/main/resources/assemblies/hadoop-yarn-dist.xml

@@ -195,7 +195,7 @@
     </fileSet>
     <fileSet>
       <directory>hadoop-yarn/hadoop-yarn-ui/target/hadoop-yarn-ui-${project.version}</directory>
-      <outputDirectory>/share/hadoop/${hadoop.component}/webapps/rm</outputDirectory>
+      <outputDirectory>/share/hadoop/${hadoop.component}/webapps/ui2</outputDirectory>
       <includes>
         <include>**/*</include>
       </includes>
@@ -207,6 +207,9 @@
         <include>org.apache.hadoop:hadoop-yarn-server-timelineservice</include>
         <include>org.apache.hadoop:hadoop-yarn-server-timelineservice-hbase</include>
       </includes>
+      <excludes>
+        <exclude>org.apache.hadoop:hadoop-yarn-ui</exclude>
+      </excludes>
       <binaries>
         <outputDirectory>share/hadoop/${hadoop.component}/timelineservice</outputDirectory>
         <includeDependencies>false</includeDependencies>

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/ResourceManager.java

@@ -1082,33 +1082,48 @@ public class ResourceManager extends CompositeService implements Recoverable {
     WebAppContext uiWebAppContext = null;
     if (getConfig().getBoolean(YarnConfiguration.YARN_WEBAPP_UI2_ENABLE,
         YarnConfiguration.DEFAULT_YARN_WEBAPP_UI2_ENABLE)) {
-      String webPath = UI2_WEBAPP_NAME;
       String onDiskPath = getConfig()
           .get(YarnConfiguration.YARN_WEBAPP_UI2_WARFILE_PATH);
 
+      uiWebAppContext = new WebAppContext();
+      uiWebAppContext.setContextPath(UI2_WEBAPP_NAME);
+
       if (null == onDiskPath) {
         String war = "hadoop-yarn-ui-" + VersionInfo.getVersion() + ".war";
         URLClassLoader cl = (URLClassLoader) ClassLoader.getSystemClassLoader();
         URL url = cl.findResource(war);
 
         if (null == url) {
-          onDiskPath = "";
+          onDiskPath = getWebAppsPath("ui2");
         } else {
           onDiskPath = url.getFile();
         }
-
-        LOG.info(
-            "New web UI war file name:" + war + ", and path:" + onDiskPath);
       }
 
-      uiWebAppContext = new WebAppContext();
-      uiWebAppContext.setContextPath(webPath);
-      uiWebAppContext.setWar(onDiskPath);
+      if (onDiskPath == null || onDiskPath.isEmpty()) {
+          LOG.error("No war file or webapps found for ui2 !");
+      } else {
+        if (onDiskPath.endsWith(".war")) {
+          uiWebAppContext.setWar(onDiskPath);
+          LOG.info("Using war file at: " + onDiskPath);
+        } else {
+          uiWebAppContext.setResourceBase(onDiskPath);
+          LOG.info("Using webapps at: " + onDiskPath);
+        }
+      }
     }
 
     webApp = builder.start(new RMWebApp(this), uiWebAppContext);
   }
 
+  private String getWebAppsPath(String appName) {
+    URL url = getClass().getClassLoader().getResource("webapps/" + appName);
+    if (url == null) {
+      return "";
+    }
+    return url.toString();
+  }
+
   /**
    * Helper method to create and init {@link #activeServices}. This creates an
    * instance of {@link RMActiveServices} and initializes it.