HDFS-11711. DN should not delete the block On "Too many open files" Exception. Contributed by Brahma Reddy Battula.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockSender.java

@@ -302,6 +302,7 @@ class BlockSender implements java.io.Closeable {
         LengthInputStream metaIn = null;
         boolean keepMetaInOpen = false;
         try {
+          DataNodeFaultInjector.get().throwTooManyOpenFiles();
           metaIn = datanode.data.getMetaDataInputStream(block);
           if (!corruptChecksumOk || metaIn != null) {
             if (metaIn == null) {
@@ -331,10 +332,14 @@ class BlockSender implements java.io.Closeable {
             LOG.warn("Could not find metadata file for " + block);
           }
         } catch (FileNotFoundException e) {
+          if ((e.getMessage() != null) && !(e.getMessage()
+              .contains("Too many open files"))) {
             // The replica is on its volume map but not on disk
-          datanode.notifyNamenodeDeletedBlock(block, replica.getStorageUuid());
+            datanode
+                .notifyNamenodeDeletedBlock(block, replica.getStorageUuid());
             datanode.data.invalidate(block.getBlockPoolId(),
-              new Block[]{block.getLocalBlock()});
+                new Block[] {block.getLocalBlock()});
+          }
           throw e;
         } finally {
           if (!keepMetaInOpen) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNodeFaultInjector.java

@@ -21,6 +21,7 @@
 
 import org.apache.hadoop.classification.InterfaceAudience;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 
 /**
@@ -85,4 +86,7 @@ public void failPipeline(ReplicaInPipeline replicaInfo,
   public void startOfferService() throws Exception {}
 
   public void endOfferService() throws Exception {}
+
+  public void throwTooManyOpenFiles() throws FileNotFoundException {
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeMetrics.java

@@ -24,8 +24,10 @@
 import static org.junit.Assert.*;
 
 import java.io.Closeable;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.lang.management.ManagementFactory;
+import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.List;
 
@@ -45,8 +47,10 @@
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.StartupOption;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.metrics2.MetricsRecordBuilder;
@@ -365,4 +369,62 @@ public void testDatanodeActiveXceiversCount() throws Exception {
       }
     }
   }
+
+  @Test
+  public void testDNShouldNotDeleteBlockONTooManyOpenFiles()
+      throws Exception {
+    Configuration conf = new HdfsConfiguration();
+    conf.setLong(DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY, 1L);
+    conf.setLong(HdfsClientConfigKeys.Retry.WINDOW_BASE_KEY, 1);
+    DataNodeFaultInjector oldInjector = DataNodeFaultInjector.get();
+    MiniDFSCluster cluster =
+        new MiniDFSCluster.Builder(conf).numDataNodes(1).build();
+    final DataNodeFaultInjector injector =
+        Mockito.mock(DataNodeFaultInjector.class);
+    try {
+      // wait until the cluster is up
+      cluster.waitActive();
+      DistributedFileSystem fs = cluster.getFileSystem();
+      Path p = new Path("/testShouldThrowTMP");
+      DFSTestUtil.writeFile(fs, p, new String("testdata"));
+      //Before DN throws too many open files
+      verifyBlockLocations(fs, p, 1);
+      Mockito.doThrow(new FileNotFoundException("Too many open files")).
+          when(injector).
+          throwTooManyOpenFiles();
+      DataNodeFaultInjector.set(injector);
+      ExtendedBlock b =
+          fs.getClient().getLocatedBlocks(p.toString(), 0).get(0).getBlock();
+      try {
+        new BlockSender(b, 0, -1, false, true, true,
+                cluster.getDataNodes().get(0), null,
+                CachingStrategy.newDefaultStrategy());
+        fail("Must throw FileNotFoundException");
+      } catch (FileNotFoundException fe) {
+        assertTrue("Should throw too many open files",
+                fe.getMessage().contains("Too many open files"));
+      }
+      cluster.triggerHeartbeats(); // IBR delete ack
+      //After DN throws too many open files
+      assertTrue(cluster.getDataNodes().get(0).getFSDataset().isValidBlock(b));
+      verifyBlockLocations(fs, p, 1);
+    } finally {
+      if (cluster != null) {
+        cluster.shutdown();
+      }
+      DataNodeFaultInjector.set(oldInjector);
+    }
+  }
+
+  private void verifyBlockLocations(DistributedFileSystem fs, Path p,
+      int expected) throws IOException, TimeoutException, InterruptedException {
+    final LocatedBlock lb =
+        fs.getClient().getLocatedBlocks(p.toString(), 0).get(0);
+    GenericTestUtils.waitFor(new Supplier<Boolean>() {
+      @Override
+      public Boolean get() {
+        return lb.getLocations().length == expected;
+      }
+    }, 1000, 6000);
+  }
 }