diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index a115e68d774..c35953568c8 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -1697,6 +1697,9 @@ Release 0.23.0 - Unreleased
     MAPREDUCE-3252. Fix map tasks to not rewrite data an extra time when
     map output fits in spill buffer. (todd)
 
+    MAPREDUCE-3159. Ensure DefaultContainerExecutor doesn't delete application
+    directories during app-init. (todd via acmurthy)
+
 Release 0.22.0 - Unreleased
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DefaultContainerExecutor.java b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DefaultContainerExecutor.java
index 40ef62a18c1..9a0de4efb24 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DefaultContainerExecutor.java
+++ b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/DefaultContainerExecutor.java
@@ -340,12 +340,6 @@ public class DefaultContainerExecutor extends ContainerExecutor {
     FsPermission appperms = new FsPermission(APPDIR_PERM);
     for (Path localDir : localDirs) {
       Path fullAppDir = getApplicationDir(localDir, user, appId);
-      if (lfs.util().exists(fullAppDir)) {
-        // this will happen on a partial execution of localizeJob. Sometimes
-        // copying job.xml to the local disk succeeds but copying job.jar might
-        // throw out an exception. We should clean up and then try again.
-        lfs.delete(fullAppDir, true);
-      }
       // create $local.dir/usercache/$user/appcache/$appId
       try {
         lfs.mkdir(fullAppDir, appperms, true);
diff --git a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/LocalizedResource.java b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/LocalizedResource.java
index 1e02fe68980..883b4bcf559 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/LocalizedResource.java
+++ b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/LocalizedResource.java
@@ -205,6 +205,11 @@ public class LocalizedResource implements EventHandler<ResourceEvent> {
     // typedef
   }
 
+  /**
+   * Transition from INIT to DOWNLOADING.
+   * Sends a {@link LocalizerResourceRequestEvent} to the
+   * {@link ResourceLocalizationService}.
+   */
   @SuppressWarnings("unchecked") // dispatcher not typed
   private static class FetchResourceTransition extends ResourceTransition {
     @Override
diff --git a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java
index d5b50c8347b..22c2d3d9358 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java
+++ b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/ResourceLocalizationService.java
@@ -71,7 +71,6 @@ import org.apache.hadoop.fs.LocalDirAllocator;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.permission.FsPermission;
 import org.apache.hadoop.net.NetUtils;
-import org.apache.hadoop.security.SecurityInfo;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.yarn.YarnException;
 import org.apache.hadoop.yarn.event.Dispatcher;
@@ -320,6 +319,11 @@ public class ResourceLocalizationService extends CompositeService
           app.getAppId()));
   }
   
+  /**
+   * For each of the requested resources for a container, determines the
+   * appropriate {@link LocalResourcesTracker} and forwards a 
+   * {@link LocalResourceRequest} to that tracker.
+   */
   private void handleInitContainerResources(
       ContainerLocalizationRequestEvent rsrcReqs) {
     Container c = rsrcReqs.getContainer();
@@ -833,26 +837,7 @@ public class ResourceLocalizationService extends CompositeService
 
         // 0) init queue, etc.
         // 1) write credentials to private dir
-        DataOutputStream tokenOut = null;
-        try {
-          Credentials credentials = context.getCredentials();
-          FileContext lfs = getLocalFileContext(getConfig());
-          tokenOut =
-              lfs.create(nmPrivateCTokensPath, EnumSet.of(CREATE, OVERWRITE));
-          LOG.info("Writing credentials to the nmPrivate file "
-              + nmPrivateCTokensPath.toString() + ". Credentials list: ");
-          if (LOG.isDebugEnabled()) {
-            for (Token<? extends TokenIdentifier> tk : credentials
-                .getAllTokens()) {
-              LOG.debug(tk.getService() + " : " + tk.encodeToUrlString());
-            }
-          }
-          credentials.writeTokenStorageToStream(tokenOut);
-        } finally {
-          if (tokenOut != null) {
-            tokenOut.close();
-          }
-        }
+        writeCredentials(nmPrivateCTokensPath);
         // 2) exec initApplication and wait
         exec.startLocalizer(nmPrivateCTokensPath, localizationServerAddress,
             context.getUser(),
@@ -876,6 +861,30 @@ public class ResourceLocalizationService extends CompositeService
       }
     }
 
+    private void writeCredentials(Path nmPrivateCTokensPath)
+        throws IOException {
+      DataOutputStream tokenOut = null;
+      try {
+        Credentials credentials = context.getCredentials();
+        FileContext lfs = getLocalFileContext(getConfig());
+        tokenOut =
+            lfs.create(nmPrivateCTokensPath, EnumSet.of(CREATE, OVERWRITE));
+        LOG.info("Writing credentials to the nmPrivate file "
+            + nmPrivateCTokensPath.toString() + ". Credentials list: ");
+        if (LOG.isDebugEnabled()) {
+          for (Token<? extends TokenIdentifier> tk : credentials
+              .getAllTokens()) {
+            LOG.debug(tk.getService() + " : " + tk.encodeToUrlString());
+          }
+        }
+        credentials.writeTokenStorageToStream(tokenOut);
+      } finally {
+        if (tokenOut != null) {
+          tokenOut.close();
+        }
+      }
+    }
+
   }
 
   static class CacheCleanup extends Thread {
diff --git a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEvent.java b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEvent.java
index d3cb4afcd90..bf5097a884b 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEvent.java
+++ b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEvent.java
@@ -18,7 +18,11 @@
 package org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.event;
 
 import org.apache.hadoop.yarn.event.AbstractEvent;
+import org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.ResourceLocalizationService;
 
+/**
+ * Events delivered to the {@link ResourceLocalizationService.LocalizerTracker}
+ */
 public class LocalizerEvent extends AbstractEvent<LocalizerEventType> {
 
   private final String localizerId;
diff --git a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEventType.java b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEventType.java
index 09a1ae06607..eb033b9a3f0 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEventType.java
+++ b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerEventType.java
@@ -18,6 +18,7 @@
 package org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.event;
 
 public enum LocalizerEventType {
+  /** See {@link LocalizerResourceRequestEvent} */
   REQUEST_RESOURCE_LOCALIZATION,
   ABORT_LOCALIZATION
 }
diff --git a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerResourceRequestEvent.java b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerResourceRequestEvent.java
index f8a2c899913..4a86d763004 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerResourceRequestEvent.java
+++ b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/LocalizerResourceRequestEvent.java
@@ -20,8 +20,13 @@ package org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.eve
 import org.apache.hadoop.yarn.api.records.LocalResourceVisibility;
 import org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.LocalizedResource;
 import org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.LocalizerContext;
+import org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.ResourceLocalizationService;
 import org.apache.hadoop.yarn.util.ConverterUtils;
 
+/**
+ * Event indicating that the {@link ResourceLocalizationService.LocalizerTracker}
+ * should fetch this resource.
+ */
 public class LocalizerResourceRequestEvent extends LocalizerEvent {
 
   private final LocalizerContext context;
diff --git a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/ResourceEventType.java b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/ResourceEventType.java
index 8e84ac6902b..d68a1b6d391 100644
--- a/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/ResourceEventType.java
+++ b/hadoop-mapreduce-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/localizer/event/ResourceEventType.java
@@ -17,8 +17,17 @@
 */
 package org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.event;
 
+import org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.LocalizedResource;
+
+/**
+ * Events delivered to {@link LocalizedResource}. Each of these
+ * events is a subclass of {@link ResourceEvent}.
+ */
 public enum ResourceEventType {
+  /** See {@link ResourceRequestEvent} */
   REQUEST,
+  /** See {@link ResourceLocalizedEvent} */ 
   LOCALIZED,
+  /** See {@link ResourceReleaseEvent} */
   RELEASE
 }