commit 19318a94048818d0981efc6827a158e2263d8b69

Author: Hairong Kuang <hairong@ucdev21.inktomisearch.com>
Date:   Wed May 5 23:38:06 2010 +0000

    HADOOP:6640 from https://issues.apache.org/jira/secure/attachment/12443759/getFS_yahoo20s.patch
    
    +++ b/YAHOO-CHANGES.txt
    +    HADOOP-6640. FileSystem.get() does RPC retires within a static
    +    synchronized block. (hairong)
    +


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.20-security-patches@1077444 13f79535-47bb-0310-9956-ffa450edef68

src/core/org/apache/hadoop/fs/FileSystem.java

@@ -1399,18 +1399,32 @@ public abstract class FileSystem extends Configured implements Closeable {
   static class Cache {
     private final Map<Key, FileSystem> map = new HashMap<Key, FileSystem>();
 
-    synchronized FileSystem get(URI uri, Configuration conf) throws IOException{
+    FileSystem get(URI uri, Configuration conf) throws IOException{
       Key key = new Key(uri, conf);
-      FileSystem fs = map.get(key);
-      if (fs == null) {
-        fs = createFileSystem(uri, conf);
+      FileSystem fs = null;
+      synchronized (this) {
+        fs = map.get(key);
+      }
+      if (fs != null) {
+        return fs;
+      }
+      
+      fs = createFileSystem(uri, conf);
+      synchronized (this) {  // refetch the lock again
+        FileSystem oldfs = map.get(key);
+        if (oldfs != null) { // a file system is created while lock is releasing
+          fs.close(); // close the new file system
+          return oldfs;  // return the old file system
+        }
+
+        // now insert the new file system into the map
         if (map.isEmpty() && !clientFinalizer.isAlive()) {
           Runtime.getRuntime().addShutdownHook(clientFinalizer);
         }
         fs.key = key;
         map.put(key, fs);
+        return fs;
       }
-      return fs;
     }
 
     synchronized void remove(Key key, FileSystem fs) {

src/test/org/apache/hadoop/fs/TestFileSystemCaching.java

@@ -0,0 +1,71 @@
+/**
+ * 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.fs;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+
+import org.apache.hadoop.conf.Configuration;
+import java.util.concurrent.Semaphore;
+
+import junit.framework.TestCase;
+
+public class TestFileSystemCaching extends TestCase {
+
+  public static class InitializeForeverFileSystem extends LocalFileSystem {
+    final static Semaphore sem = new Semaphore(0);
+    public void initialize(URI uri, Configuration conf) throws IOException {
+      // notify that InitializeForeverFileSystem started initialization
+      sem.release();
+      try {
+        while (true) {
+          Thread.sleep(1000);
+        }
+      } catch (InterruptedException e) {
+        return;
+      }
+    }
+  }
+  
+  public void testCacheEnabledWithInitializeForeverFS() throws Exception {
+    final Configuration conf = new Configuration();
+    Thread t = new Thread() {
+      public void run() {
+        conf.set("fs.localfs1.impl", "org.apache.hadoop.fs." +
+         "TestFileSystemCaching$InitializeForeverFileSystem");
+        try {
+          FileSystem.get(new URI("localfs1://a"), conf);
+        } catch (IOException e) {
+          e.printStackTrace();
+        } catch (URISyntaxException e) {
+          e.printStackTrace();
+        }
+      }
+    };
+    t.start();
+    // wait for InitializeForeverFileSystem to start initialization
+    InitializeForeverFileSystem.sem.acquire();
+    
+    conf.set("fs.cachedfile.impl", conf.get("fs.file.impl"));
+    FileSystem.get(new URI("cachedfile://a"), conf);
+    t.interrupt();
+    t.join();
+  }
+}