HADOOP-5285. Adding a file that I missed in my earlier commit.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/core/trunk@746903 13f79535-47bb-0310-9956-ffa450edef68

src/mapred/org/apache/hadoop/mapred/CleanupQueue.java

@@ -0,0 +1,101 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hadoop.mapred;
+
+import java.io.IOException;
+import java.util.concurrent.LinkedBlockingQueue;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+
+class CleanupQueue {
+
+  public static final Log LOG =
+    LogFactory.getLog(CleanupQueue.class);
+
+  private static PathCleanupThread cleanupThread;
+
+  /**
+   * Create a singleton path-clean-up queue. It can be used to delete
+   * paths(directories/files) in a separate thread. This constructor creates a
+   * clean-up thread and also starts it as a daemon. Callers can instantiate one
+   * CleanupQueue per JVM and can use it for deleting paths. Use
+   * {@link CleanupQueue#addToQueue(JobConf, Path...)} to add paths for
+   * deletion.
+   */
+  public CleanupQueue() {
+    synchronized (PathCleanupThread.class) {
+      if (cleanupThread == null) {
+        cleanupThread = new PathCleanupThread();
+      }
+    }
+  }
+  
+  public void addToQueue(JobConf conf, Path...paths) {
+    cleanupThread.addToQueue(conf,paths);
+  }
+
+  private static class PathCleanupThread extends Thread {
+
+    static class PathAndConf {
+      JobConf conf;
+      Path path;
+      PathAndConf(JobConf conf, Path path) {
+        this.conf = conf;
+        this.path = path;
+      }
+    }
+    // cleanup queue which deletes files/directories of the paths queued up.
+    private LinkedBlockingQueue<PathAndConf> queue = new LinkedBlockingQueue<PathAndConf>();
+
+    public PathCleanupThread() {
+      setName("Directory/File cleanup thread");
+      setDaemon(true);
+      start();
+    }
+
+    public void addToQueue(JobConf conf,Path... paths) {
+      for (Path p : paths) {
+        try {
+          queue.put(new PathAndConf(conf,p));
+        } catch (InterruptedException ie) {}
+      }
+    }
+
+    public void run() {
+      LOG.debug(getName() + " started.");
+      PathAndConf pathAndConf = null;
+      while (true) {
+        try {
+          pathAndConf = queue.take();
+          // delete the path.
+          FileSystem fs = pathAndConf.path.getFileSystem(pathAndConf.conf);
+          fs.delete(pathAndConf.path, true);
+          LOG.debug("DELETED " + pathAndConf.path);
+        } catch (IOException e) {
+          LOG.warn("Error deleting path" + pathAndConf.path);
+        } catch (InterruptedException t) {
+        }
+      }
+    }
+  }
+}