YARN-4365. FileSystemNodeLabelStore should check for root dir existence on startup. Contributed by Kuhu Shukla

(cherry picked from commit f5acf94ecafb301a0cc8e8f91f19c8bcbc8da701)

Conflicts:

	hadoop-yarn-project/CHANGES.txt
	hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/nodelabels/TestFileSystemNodeLabelsStore.java

hadoop-yarn-project/CHANGES.txt

@@ -36,6 +36,9 @@ Release 2.6.3 - UNRELEASED
     YARN-3878. AsyncDispatcher can hang while stopping if it is configured for 
     draining events on stop. (Varun Saxena via kasha)
 
+    YARN-4365. FileSystemNodeLabelStore should check for root dir existence on
+    startup (Kuhu Shukla via jlowe)
+
 Release 2.6.2 - 2015-10-28
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/nodelabels/FileSystemNodeLabelsStore.java

@@ -84,7 +84,9 @@ public class FileSystemNodeLabelsStore extends NodeLabelsStore {
     setFileSystem(conf);
 
     // mkdir of root dir path
-    fs.mkdirs(fsWorkingPath);
+    if (!fs.exists(fsWorkingPath)) {
+      fs.mkdirs(fsWorkingPath);
+    }
   }
 
   @Override
@@ -97,7 +99,7 @@ public class FileSystemNodeLabelsStore extends NodeLabelsStore {
     }
   }
 
-  private void setFileSystem(Configuration conf) throws IOException {
+  void setFileSystem(Configuration conf) throws IOException {
     Configuration confCopy = new Configuration(conf);
     confCopy.setBoolean("dfs.client.retry.policy.enabled", true);
     String retryPolicy =

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/nodelabels/TestFileSystemNodeLabelsStore.java

@@ -24,6 +24,8 @@ import java.util.Arrays;
 import java.util.Map;
 
 import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.yarn.conf.YarnConfiguration;
 import org.apache.hadoop.yarn.event.InlineDispatcher;
 import org.junit.After;
@@ -32,6 +34,7 @@ import org.junit.Before;
 import org.junit.Test;
 
 import com.google.common.collect.ImmutableMap;
+import org.mockito.Mockito;
 
 public class TestFileSystemNodeLabelsStore extends NodeLabelTestBase {
   MockNodeLabelManager mgr = null;
@@ -249,4 +252,30 @@ public class TestFileSystemNodeLabelsStore extends NodeLabelTestBase {
         Arrays.asList("p2", "p4", "p6", "p7", "p8", "p9")));
     mgr.stop();
   }
+
+  @Test
+  public void testRootMkdirOnInitStore() throws Exception {
+    final FileSystem mockFs = Mockito.mock(FileSystem.class);
+    FileSystemNodeLabelsStore mockStore = new FileSystemNodeLabelsStore(mgr) {
+      void setFileSystem(Configuration conf) throws IOException {
+        fs = mockFs;
+      }
+    };
+    mockStore.fs = mockFs;
+    verifyMkdirsCount(mockStore, true, 0);
+    verifyMkdirsCount(mockStore, false, 1);
+    verifyMkdirsCount(mockStore, true, 1);
+    verifyMkdirsCount(mockStore, false, 2);
+  }
+
+  private void verifyMkdirsCount(FileSystemNodeLabelsStore store,
+                                 boolean existsRetVal, int expectedNumOfCalls)
+      throws Exception {
+    Mockito.when(store.fs.exists(Mockito.any(
+        Path.class))).thenReturn(existsRetVal);
+    store.init(conf);
+    Mockito.verify(store.fs,Mockito.times(
+        expectedNumOfCalls)).mkdirs(Mockito.any(Path
+        .class));
+  }
 }