HDDS-11856. Set DN state machine thread priority higher than command handler thread.

hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/statemachine/DatanodeStateMachine.java

@@ -555,6 +555,7 @@ public void startDaemon() {
           ExitUtils.terminate(1, message, ex, LOG);
         })
         .build().newThread(startStateMachineTask);
+    stateMachineThread.setPriority(Thread.MAX_PRIORITY);
     stateMachineThread.start();
   }
 
@@ -678,6 +679,7 @@ private void initCommandHandlerThread(ConfigurationSource config) {
 
     // We will have only one thread for command processing in a datanode.
     cmdProcessThread = getCommandHandlerThread(processCommandQueue);
+    cmdProcessThread.setPriority(Thread.NORM_PRIORITY);
     cmdProcessThread.start();
   }
 
@@ -745,4 +747,15 @@ public DatanodeQueueMetrics getQueueMetrics() {
   public ReconfigurationHandler getReconfigurationHandler() {
     return reconfigurationHandler;
   }
+
+  @VisibleForTesting
+  public Thread getStateMachineThread() {
+    return stateMachineThread;
+  }
+
+  @VisibleForTesting
+  public Thread getCmdProcessThread() {
+    return cmdProcessThread;
+  }
+
 }

hadoop-hdds/container-service/src/test/java/org/apache/hadoop/ozone/container/common/TestDatanodeStateMachine.java

@@ -404,6 +404,26 @@ public void testDatanodeStateMachineWithInvalidConfiguration()
     });
   }
 
+  @Test
+  public void testStateMachineThreadPriority() throws Exception {
+    DatanodeDetails datanodeDetails = getNewDatanodeDetails();
+    DatanodeDetails.Port port = DatanodeDetails.newStandalonePort(
+        OzoneConfigKeys.HDDS_CONTAINER_IPC_PORT_DEFAULT);
+    datanodeDetails.setPort(port);
+    try (DatanodeStateMachine stateMachine =
+             new DatanodeStateMachine(datanodeDetails, conf)) {
+      stateMachine.startDaemon();
+
+      // Wait for CmdProcessThread to initialize
+      GenericTestUtils.waitFor(()
+          ->  stateMachine.getCmdProcessThread() != null, 100, 3000);
+      Thread stateMachineThread = stateMachine.getStateMachineThread();
+      Thread cmdProcessThread = stateMachine.getCmdProcessThread();
+      // stateMachineThread priority is higher than cmdProcessThread
+      assertTrue(stateMachineThread.getPriority() > cmdProcessThread.getPriority());
+    }
+  }
+
   private DatanodeDetails getNewDatanodeDetails() {
     DatanodeDetails.Port containerPort = DatanodeDetails.newStandalonePort(0);
     DatanodeDetails.Port ratisPort = DatanodeDetails.newRatisPort(0);