HDFS-8300. Fix unit test failures and findbugs warning caused by HDFS-8283. Contributed by Jing Zhao.

(cherry picked from commit 98a6176628)

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

@@ -268,6 +268,9 @@ Release 2.8.0 - UNRELEASED
 
     HDFS-8214. Secondary NN Web UI shows wrong date for Last Checkpoint. (clamb via wang)
 
+    HDFS-8300. Fix unit test failures and findbugs warning caused by HDFS-8283.
+    (jing9)
+
 Release 2.7.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -767,7 +767,7 @@ public class DFSOutputStream extends FSOutputSummer
 
   protected synchronized void closeImpl() throws IOException {
     if (isClosed()) {
-      streamer.getLastException().check();
+      streamer.getLastException().check(true);
       return;
     }
 

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

@@ -174,13 +174,13 @@ class DataStreamer extends Daemon {
     packets.clear();
   }
   
-  static class LastException {
-    private Throwable thrown;
+  static class LastExceptionInStreamer {
+    private IOException thrown;
 
     synchronized void set(Throwable t) {
-      Preconditions.checkNotNull(t);
-      Preconditions.checkState(thrown == null);
-      this.thrown = t;
+      assert t != null;
+      this.thrown = t instanceof IOException ?
+          (IOException) t : new IOException(t);
     }
 
     synchronized void clear() {
@@ -188,17 +188,23 @@ class DataStreamer extends Daemon {
     }
 
     /** Check if there already is an exception. */
-    synchronized void check() throws IOException {
+    synchronized void check(boolean resetToNull) throws IOException {
       if (thrown != null) {
-        throw new IOException(thrown);
+        if (LOG.isTraceEnabled()) {
+          // wrap and print the exception to know when the check is called
+          LOG.trace("Got Exception while checking", new Throwable(thrown));
+        }
+        final IOException e = thrown;
+        if (resetToNull) {
+          thrown = null;
+        }
+        throw e;
       }
     }
 
     synchronized void throwException4Close() throws IOException {
-      check();
-      final IOException ioe = new ClosedChannelException();
-      thrown = ioe;
-      throw ioe;
+      check(false);
+      throw new ClosedChannelException();
     }
   }
 
@@ -234,7 +240,7 @@ class DataStreamer extends Daemon {
   private long lastQueuedSeqno = -1;
   private long lastAckedSeqno = -1;
   private long bytesCurBlock = 0; // bytes written in current block
-  private final LastException lastException = new LastException();
+  private final LastExceptionInStreamer lastException = new LastExceptionInStreamer();
   private Socket s;
 
   private final DFSClient dfsClient;
@@ -1741,7 +1747,7 @@ class DataStreamer extends Daemon {
   /**
    * @return the last exception
    */
-  LastException getLastException(){
+  LastExceptionInStreamer getLastException(){
     return lastException;
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestDFSOutputStream.java

@@ -28,6 +28,7 @@ import java.util.concurrent.atomic.AtomicReference;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hdfs.DataStreamer.LastExceptionInStreamer;
 import org.apache.hadoop.hdfs.client.impl.DfsClientConf;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
@@ -65,9 +66,10 @@ public class TestDFSOutputStream {
     DataStreamer streamer = (DataStreamer) Whitebox
         .getInternalState(dos, "streamer");
     @SuppressWarnings("unchecked")
-    AtomicReference<IOException> ex = (AtomicReference<IOException>) Whitebox
+    LastExceptionInStreamer ex = (LastExceptionInStreamer) Whitebox
         .getInternalState(streamer, "lastException");
-    Assert.assertEquals(null, ex.get());
+    Throwable thrown = (Throwable) Whitebox.getInternalState(ex, "thrown");
+    Assert.assertNull(thrown);
 
     dos.close();
 
@@ -78,7 +80,8 @@ public class TestDFSOutputStream {
     } catch (IOException e) {
       Assert.assertEquals(e, dummy);
     }
-    Assert.assertEquals(null, ex.get());
+    thrown = (Throwable) Whitebox.getInternalState(ex, "thrown");
+    Assert.assertNull(thrown);
     dos.close();
   }