HBASE-23615 Use a dedicated thread for executing WorkerMonitor in Pro… (#961)

Signed-off-by: stack <stack@apache.org>
Signed-off-by: Duo Zhang <zhangduo@apache.org>
Signed-off-by: virajjasani <34790606+virajjasani@users.noreply.github.com>

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/ProcedureExecutor.java

@@ -217,6 +217,15 @@ public class ProcedureExecutor<TEnvironment> {
    */
   private TimeoutExecutorThread<TEnvironment> timeoutExecutor;
 
+  /**
+   * WorkerMonitor check for stuck workers and new worker thread when necessary, for example if
+   * there is no worker to assign meta, it will new worker thread for it, so it is very important.
+   * TimeoutExecutor execute many tasks like DeadServerMetricRegionChore RegionInTransitionChore
+   * and so on, some tasks may execute for a long time so will block other tasks like
+   * WorkerMonitor, so use a dedicated thread for executing WorkerMonitor.
+   */
+  private TimeoutExecutorThread<TEnvironment> workerMonitorExecutor;
+
   private int corePoolSize;
   private int maxPoolSize;
 
@@ -560,7 +569,8 @@ public class ProcedureExecutor<TEnvironment> {
         corePoolSize, maxPoolSize);
 
     this.threadGroup = new ThreadGroup("PEWorkerGroup");
-    this.timeoutExecutor = new TimeoutExecutorThread<>(this, threadGroup);
+    this.timeoutExecutor = new TimeoutExecutorThread<>(this, threadGroup, "ProcExecTimeout");
+    this.workerMonitorExecutor = new TimeoutExecutorThread<>(this, threadGroup, "WorkerMonitor");
 
     // Create the workers
     workerId.set(0);
@@ -604,12 +614,13 @@ public class ProcedureExecutor<TEnvironment> {
     // Start the executors. Here we must have the lastProcId set.
     LOG.trace("Start workers {}", workerThreads.size());
     timeoutExecutor.start();
+    workerMonitorExecutor.start();
     for (WorkerThread worker: workerThreads) {
       worker.start();
     }
 
     // Internal chores
-    timeoutExecutor.add(new WorkerMonitor());
+    workerMonitorExecutor.add(new WorkerMonitor());
 
     // Add completed cleaner chore
     addChore(new CompletedProcedureCleaner<>(conf, store, procExecutionLock, completed,
@@ -624,6 +635,7 @@ public class ProcedureExecutor<TEnvironment> {
     LOG.info("Stopping");
     scheduler.stop();
     timeoutExecutor.sendStopSignal();
+    workerMonitorExecutor.sendStopSignal();
   }
 
   @VisibleForTesting
@@ -632,6 +644,8 @@ public class ProcedureExecutor<TEnvironment> {
 
     // stop the timeout executor
     timeoutExecutor.awaitTermination();
+    // stop the work monitor executor
+    workerMonitorExecutor.awaitTermination();
 
     // stop the worker threads
     for (WorkerThread worker: workerThreads) {

hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/TimeoutExecutorThread.java

@@ -37,8 +37,9 @@ class TimeoutExecutorThread<TEnvironment> extends StoppableThread {
 
   private final DelayQueue<DelayedWithTimeout> queue = new DelayQueue<>();
 
-  public TimeoutExecutorThread(ProcedureExecutor<TEnvironment> executor, ThreadGroup group) {
-    super(group, "ProcExecTimeout");
+  public TimeoutExecutorThread(ProcedureExecutor<TEnvironment> executor, ThreadGroup group,
+    String name) {
+    super(group, name);
     setDaemon(true);
     this.executor = executor;
   }

hbase-server/src/test/java/org/apache/hadoop/hbase/master/procedure/TestProcedureAdmin.java

@@ -57,7 +57,6 @@ public class TestProcedureAdmin {
 
   protected static final HBaseTestingUtility UTIL = new HBaseTestingUtility();
 
-
   private static void setupConf(Configuration conf) {
     conf.setInt(MasterProcedureConstants.MASTER_PROCEDURE_THREADS, 1);
   }