HDFS-10271. Extra bytes are getting released from reservedSpace for append (Contributed by Brahma Reddy Battula)

(cherry picked from commit a9a607f8fc0d996af3fb37f7efa7591d6655900d)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java

@@ -1164,7 +1164,8 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     // construct a RBW replica with the new GS
     File blkfile = replicaInfo.getBlockFile();
     FsVolumeImpl v = (FsVolumeImpl)replicaInfo.getVolume();
-    if (v.getAvailable() < estimateBlockLen - replicaInfo.getNumBytes()) {
+    long bytesReserved = estimateBlockLen - replicaInfo.getNumBytes();
+    if (v.getAvailable() < bytesReserved) {
       throw new DiskOutOfSpaceException("Insufficient space for appending to "
           + replicaInfo);
     }
@@ -1172,7 +1173,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     File oldmeta = replicaInfo.getMetaFile();
     ReplicaBeingWritten newReplicaInfo = new ReplicaBeingWritten(
         replicaInfo.getBlockId(), replicaInfo.getNumBytes(), newGS,
-        v, newBlkFile.getParentFile(), Thread.currentThread(), estimateBlockLen);
+        v, newBlkFile.getParentFile(), Thread.currentThread(), bytesReserved);
     File newmeta = newReplicaInfo.getMetaFile();
 
     // rename meta file to rbw directory
@@ -1208,7 +1209,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     
     // Replace finalized replica by a RBW replica in replicas map
     volumeMap.add(bpid, newReplicaInfo);
-    v.reserveSpaceForReplica(estimateBlockLen - replicaInfo.getNumBytes());
+    v.reserveSpaceForReplica(bytesReserved);
     return newReplicaInfo;
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestSpaceReservation.java

@@ -572,4 +572,64 @@ public class TestSpaceReservation {
       return numFailures;
     }
   }
+
+  @Test(timeout = 30000)
+  public void testReservedSpaceForAppend() throws Exception {
+    final short replication = 3;
+    startCluster(BLOCK_SIZE, replication, -1);
+    final String methodName = GenericTestUtils.getMethodName();
+    final Path file = new Path("/" + methodName + ".01.dat");
+
+    // Write 1 byte to the file and kill the writer.
+    FSDataOutputStream os = fs.create(file, replication);
+    os.write(new byte[1024]);
+    os.close();
+
+    final Path file2 = new Path("/" + methodName + ".02.dat");
+
+    // Write 1 byte to the file and keep it open.
+    FSDataOutputStream os2 = fs.create(file2, replication);
+    os2.write(new byte[1]);
+    os2.hflush();
+    int expectedFile2Reserved = BLOCK_SIZE - 1;
+    checkReservedSpace(expectedFile2Reserved);
+
+    // append one byte and verify reservedspace before and after closing
+    os = fs.append(file);
+    os.write(new byte[1]);
+    os.hflush();
+    int expectedFile1Reserved = BLOCK_SIZE - 1025;
+    checkReservedSpace(expectedFile2Reserved + expectedFile1Reserved);
+    os.close();
+    checkReservedSpace(expectedFile2Reserved);
+
+    // append one byte and verify reservedspace before and after abort
+    os = fs.append(file);
+    os.write(new byte[1]);
+    os.hflush();
+    expectedFile1Reserved--;
+    checkReservedSpace(expectedFile2Reserved + expectedFile1Reserved);
+    DFSTestUtil.abortStream(((DFSOutputStream) os.getWrappedStream()));
+    checkReservedSpace(expectedFile2Reserved);
+  }
+
+  private void checkReservedSpace(final long expectedReserved) throws TimeoutException,
+      InterruptedException, IOException {
+    for (final DataNode dn : cluster.getDataNodes()) {
+      try (FsDatasetSpi.FsVolumeReferences volumes = dn.getFSDataset()
+          .getFsVolumeReferences()) {
+        final FsVolumeImpl volume = (FsVolumeImpl) volumes.get(0);
+        GenericTestUtils.waitFor(new Supplier<Boolean>() {
+          @Override
+          public Boolean get() {
+            LOG.info(
+                "dn " + dn.getDisplayName() + " space : " + volume
+                    .getReservedForReplicas() + ", Expected ReservedSpace :"
+                    + expectedReserved);
+            return (volume.getReservedForReplicas() == expectedReserved);
+          }
+        }, 100, 3000);
+      }
+    }
+  }
 }