Merge -c 1391671 from trunk to branch-2.0.2-alpha to fix MAPREDUCE-4691. Historyserver can report 'Unknown job' after RM says job has completed. Contributed by Robert Evans.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.0.2-alpha@1391933 13f79535-47bb-0310-9956-ffa450edef68

hadoop-mapreduce-project/CHANGES.txt

@@ -396,6 +396,9 @@ Release 0.23.4 - UNRELEASED
     MAPREDUCE-4647. We should only unjar jobjar if there is a lib directory 
     in it. (Robert Evans via tgraves)
 
+    MAPREDUCE-4691. Historyserver can report "Unknown job" after RM says job
+    has completed (Robert Joseph Evans via jlowe)
+
 Release 0.23.3 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-hs/src/main/java/org/apache/hadoop/mapreduce/v2/hs/HistoryFileManager.java

@@ -23,14 +23,14 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.TreeMap;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadFactory;
@@ -77,7 +77,7 @@ public class HistoryFileManager extends AbstractService {
   private static enum HistoryInfoState {
     IN_INTERMEDIATE, IN_DONE, DELETED, MOVE_FAILED
   };
-
+  
   private static String DONE_BEFORE_SERIAL_TAIL = JobHistoryUtils
       .doneSubdirsBeforeSerialTail();
 
@@ -199,6 +199,29 @@ public class HistoryFileManager extends AbstractService {
     }
   }
 
+  /**
+   * This class represents a user dir in the intermediate done directory.  This
+   * is mostly for locking purposes. 
+   */
+  private class UserLogDir {
+    long modTime = 0;
+    
+    public synchronized void scanIfNeeded(FileStatus fs) {
+      long newModTime = fs.getModificationTime();
+      if (modTime != newModTime) {
+        Path p = fs.getPath();
+        try {
+          scanIntermediateDirectory(p);
+          //If scanning fails, we will scan again.  We assume the failure is
+          // temporary.
+          modTime = newModTime;
+        } catch (IOException e) {
+          LOG.error("Error while trying to scan the directory " + p, e);
+        }
+      }
+    }
+  }
+  
   public class HistoryFileInfo {
     private Path historyFile;
     private Path confFile;
@@ -352,7 +375,8 @@ public class HistoryFileManager extends AbstractService {
    * Maintains a mapping between intermediate user directories and the last
    * known modification time.
    */
-  private Map<String, Long> userDirModificationTimeMap = new HashMap<String, Long>();
+  private ConcurrentMap<String, UserLogDir> userDirModificationTimeMap = 
+    new ConcurrentHashMap<String, UserLogDir>();
 
   private JobACLsManager aclsMgr;
 
@@ -584,23 +608,15 @@ public class HistoryFileManager extends AbstractService {
 
     for (FileStatus userDir : userDirList) {
       String name = userDir.getPath().getName();
-      long newModificationTime = userDir.getModificationTime();
-      boolean shouldScan = false;
-      synchronized (userDirModificationTimeMap) {
-        if (!userDirModificationTimeMap.containsKey(name)
-            || newModificationTime > userDirModificationTimeMap.get(name)) {
-          shouldScan = true;
-          userDirModificationTimeMap.put(name, newModificationTime);
-        }
-      }
-      if (shouldScan) {
-        try {
-          scanIntermediateDirectory(userDir.getPath());
-        } catch (IOException e) {
-          LOG.error("Error while trying to scan the directory " 
-              + userDir.getPath(), e);
+      UserLogDir dir = userDirModificationTimeMap.get(name);
+      if(dir == null) {
+        dir = new UserLogDir();
+        UserLogDir old = userDirModificationTimeMap.putIfAbsent(name, dir);
+        if(old != null) {
+          dir = old;
         }
       }
+      dir.scanIfNeeded(userDir);
     }
   }