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-1@1382413 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -228,6 +228,9 @@ Release 1.2.0 - unreleased
     HADOOP-8745. Incorrect version numbers in hadoop-core POM.
     (Matthias Friedrich via eli)
 
+    HDFS-2757. Cannot read a local block that's being written to when
+    using the local read short circuit. (Jean-Daniel Cryans via eli)
+
 Release 1.1.0 - unreleased
 
   INCOMPATIBLE CHANGES

src/hdfs/org/apache/hadoop/hdfs/DFSClient.java

@@ -2019,6 +2019,10 @@ public class DFSClient implements FSConstants, java.io.Closeable {
       return (locatedBlocks == null) ? 0 : locatedBlocks.getFileLength();
     }
 
+    private synchronized boolean blockUnderConstruction() {
+      return locatedBlocks.isUnderConstruction();
+    }
+
     /**
      * Returns the datanode from which the stream is currently reading.
      */
@@ -2130,10 +2134,9 @@ public class DFSClient implements FSConstants, java.io.Closeable {
 
     private boolean shouldTryShortCircuitRead(InetSocketAddress targetAddr)
         throws IOException {
-      if (shortCircuitLocalReads && isLocalAddress(targetAddr)) {
-        return true;
-      }
-      return false;
+      // Can't local read a block under construction, see HDFS-2757
+      return shortCircuitLocalReads && !blockUnderConstruction()
+        && isLocalAddress(targetAddr);
     }
     
     /**