HDFS-16535. SlotReleaser should reuse the domain socket based on socket paths

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/shortcircuit/ShortCircuitCache.java

@@ -189,16 +189,18 @@ public void run() {
       final DfsClientShm shm = (DfsClientShm)slot.getShm();
       final DomainSocket shmSock = shm.getPeer().getDomainSocket();
       final String path = shmSock.getPath();
+      DomainSocket domainSocket = pathToDomainSocket.get(path);
       DataOutputStream out = null;
       boolean success = false;
       int retries = 2;
       try {
         while (retries > 0) {
           try {
             if (domainSocket == null || !domainSocket.isOpen()) {
-              // we are running in single thread mode, no protection needed for
-              // domainSocket
               domainSocket = DomainSocket.connect(path);
+              // we are running in single thread mode, no protection needed for
+              // pathToDomainSocket
+              pathToDomainSocket.put(path, domainSocket);
             }
 
             out = new DataOutputStream(
@@ -221,8 +223,11 @@ public void run() {
           } catch (SocketException se) {
             // the domain socket on datanode may be timed out, we retry once
             retries--;
-            domainSocket.close();
-            domainSocket = null;
+            if (domainSocket != null) {
+              domainSocket.close();
+              domainSocket = null;
+              pathToDomainSocket.remove(path);
+            }
             if (retries == 0) {
               throw new SocketException("Create domain socket failed");
             }
@@ -240,7 +245,7 @@ public void run() {
         } else {
           shm.getEndpointShmManager().shutdown(shm);
           IOUtilsClient.cleanupWithLogger(LOG, domainSocket, out);
-          domainSocket = null;
+          pathToDomainSocket.remove(path);
         }
       }
     }
@@ -354,7 +359,11 @@ public interface ShortCircuitReplicaCreator {
    */
   private final DfsClientShmManager shmManager;
 
-  private DomainSocket domainSocket = null;
+  /**
+   * A map contains all DomainSockets used in SlotReleaser. Keys are the domain socket
+   * paths of short-circuit shared memory segments.
+   */
+  private Map<String, DomainSocket> pathToDomainSocket = new HashMap<>();
 
   public static ShortCircuitCache fromConf(ShortCircuitConf conf) {
     return new ShortCircuitCache(

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/shortcircuit/TestShortCircuitCache.java

@@ -63,6 +63,7 @@
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader;
+import org.apache.hadoop.hdfs.server.datanode.DataNode;
 import org.apache.hadoop.hdfs.server.datanode.DataNodeFaultInjector;
 import org.apache.hadoop.hdfs.server.datanode.ShortCircuitRegistry;
 import org.apache.hadoop.hdfs.server.datanode.ShortCircuitRegistry.RegisteredShm;
@@ -957,6 +958,83 @@ public void testDomainSocketClosedByDN() throws Exception {
     }
   }
 
+  // Regression test for HDFS-16473
+  @Test(timeout = 60000)
+  public void testDomainSocketClosedByMultipleDNs() throws Exception {
+    TemporarySocketDirectory sockDir = new TemporarySocketDirectory();
+    String testName = "testDomainSocketClosedByMultipleDNs";
+    Configuration conf = createShortCircuitConf(testName, sockDir);
+    conf.set(DFS_DOMAIN_SOCKET_PATH_KEY, new File(sockDir.getDir(),
+        testName + "._PORT").getAbsolutePath());
+    MiniDFSCluster cluster =
+        new MiniDFSCluster.Builder(conf).numDataNodes(2).build();
+
+    try {
+      cluster.waitActive();
+      DistributedFileSystem fs = cluster.getFileSystem();
+      final ShortCircuitCache cache =
+          fs.getClient().getClientContext().getShortCircuitCache();
+
+      ExtendedBlockId blockId0 = new ExtendedBlockId(123, "xyz");
+      ExtendedBlockId blockId1 = new ExtendedBlockId(456, "xyz");
+
+      DataNode dn0 = cluster.getDataNodes().get(0);
+      DataNode dn1 = cluster.getDataNodes().get(1);
+
+      DomainPeer peer0 = new DomainPeer(DomainSocket.connect(new File(
+          sockDir.getDir(), testName + "." + dn0.getXferPort()).getAbsolutePath()));
+      DomainPeer peer1 = new DomainPeer(DomainSocket.connect(new File(
+          sockDir.getDir(), testName + "." + dn1.getXferPort()).getAbsolutePath()));
+
+      final DatanodeInfo dnInfo0 = new DatanodeInfo.DatanodeInfoBuilder()
+          .setNodeID(dn0.getDatanodeId()).build();
+      final DatanodeInfo dnInfo1 = new DatanodeInfo.DatanodeInfoBuilder()
+          .setNodeID(dn1.getDatanodeId()).build();
+
+      // Allocate 2 shm slots from DataNode-0
+      MutableBoolean usedPeer = new MutableBoolean(false);
+      Slot slot1 = cache.allocShmSlot(dnInfo0, peer0, usedPeer, blockId0,
+          "testDomainSocketClosedByMultipleDNs_client");
+      dn0.getShortCircuitRegistry()
+          .registerSlot(blockId0, slot1.getSlotId(), false);
+
+      Slot slot2 = cache.allocShmSlot(dnInfo0, peer0, usedPeer, blockId0,
+          "testDomainSocketClosedByMultipleDNs_client");
+      dn0.getShortCircuitRegistry()
+          .registerSlot(blockId0, slot2.getSlotId(), false);
+
+      // Allocate 1 shm slot from DataNode-1
+      Slot slot3 = cache.allocShmSlot(dnInfo1, peer1, usedPeer, blockId1,
+          "testDomainSocketClosedByMultipleDNs_client");
+      dn1.getShortCircuitRegistry()
+          .registerSlot(blockId1, slot3.getSlotId(), false);
+
+      Assert.assertEquals(2, cache.getDfsClientShmManager().getShmNum());
+      Assert.assertEquals(1, dn0.getShortCircuitRegistry().getShmNum());
+      Assert.assertEquals(1, dn1.getShortCircuitRegistry().getShmNum());
+
+      // Release the slot of DataNode-1 first.
+      cache.scheduleSlotReleaser(slot3);
+      Thread.sleep(2000);
+      Assert.assertEquals(1, cache.getDfsClientShmManager().getShmNum());
+
+      // Release the slots of DataNode-0.
+      cache.scheduleSlotReleaser(slot1);
+      Thread.sleep(2000);
+      Assert.assertEquals("0 ShmNum means the shm of DataNode-0 is shutdown" +
+              " due to slot release failures.",
+          1, cache.getDfsClientShmManager().getShmNum());
+      cache.scheduleSlotReleaser(slot2);
+      Thread.sleep(2000);
+
+      Assert.assertEquals(0, dn0.getShortCircuitRegistry().getShmNum());
+      Assert.assertEquals(0, dn1.getShortCircuitRegistry().getShmNum());
+      Assert.assertEquals(0, cache.getDfsClientShmManager().getShmNum());
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
   @Test(timeout = 60000)
   public void testDNRestart() throws Exception {
     TemporarySocketDirectory sockDir = new TemporarySocketDirectory();