HDFS-2757. Cannot read a local block that's being written to when using the local read short circuit. Contributed by Jean-Daniel Cryans

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1382410 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -577,6 +577,9 @@ Release 2.0.2-alpha - 2012-09-07
     (Andy Isaacson via eli)
 
     HDFS-3895. hadoop-client must include commons-cli (tucu)
+
+    HDFS-2757. Cannot read a local block that's being written to when
+    using the local read short circuit. (Jean-Daniel Cryans via eli)
     
   BREAKDOWN OF HDFS-3042 SUBTASKS
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -2112,10 +2112,7 @@ public class DFSClient implements java.io.Closeable {
   }
   
   boolean shouldTryShortCircuitRead(InetSocketAddress targetAddr) {
-    if (shortCircuitLocalReads && isLocalAddress(targetAddr)) {
-      return true;
-    }
-    return false;
+    return shortCircuitLocalReads && isLocalAddress(targetAddr);
   }
 
   void reportChecksumFailure(String file, ExtendedBlock blk, DatanodeInfo dn) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java

@@ -243,6 +243,10 @@ public class DFSInputStream extends FSInputStream implements ByteBufferReadable
         locatedBlocks.getFileLength() + lastBlockBeingWrittenLength;
   }
 
+  private synchronized boolean blockUnderConstruction() {
+    return locatedBlocks.isUnderConstruction();
+  }
+
   /**
    * Returns the datanode from which the stream is currently reading.
    */
@@ -878,7 +882,9 @@ public class DFSInputStream extends FSInputStream implements ByteBufferReadable
                                        String clientName)
       throws IOException {
     
-    if (dfsClient.shouldTryShortCircuitRead(dnAddr)) {
+    // Can't local read a block under construction, see HDFS-2757
+    if (dfsClient.shouldTryShortCircuitRead(dnAddr) &&
+        !blockUnderConstruction()) {
       return DFSClient.getLocalBlockReader(dfsClient.conf, src, block,
           blockToken, chosenNode, dfsClient.hdfsTimeout, startOffset,
           dfsClient.connectToDnViaHostname());