YARN-5543. ResourceManager SchedulingMonitor could potentially terminate the preemption checker thread. Contributed by Min Shen.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/SchedulingMonitor.java

@@ -17,6 +17,12 @@
  */
 package org.apache.hadoop.yarn.server.resourcemanager.monitor;
 
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.TimeUnit;
+
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.conf.Configuration;
@@ -32,9 +38,10 @@ public class SchedulingMonitor extends AbstractService {
   private final SchedulingEditPolicy scheduleEditPolicy;
   private static final Log LOG = LogFactory.getLog(SchedulingMonitor.class);
 
-  //thread which runs periodically to see the last time since a heartbeat is
-  //received.
-  private Thread checkerThread;
+  // ScheduledExecutorService which schedules the PreemptionChecker to run
+  // periodically.
+  private ScheduledExecutorService ses;
+  private ScheduledFuture<?> handler;
   private volatile boolean stopped;
   private long monitorInterval;
   private RMContext rmContext;
@@ -61,17 +68,25 @@ public class SchedulingMonitor extends AbstractService {
   @Override
   public void serviceStart() throws Exception {
     assert !stopped : "starting when already stopped";
-    checkerThread = new Thread(new PreemptionChecker());
-    checkerThread.setName(getName());
-    checkerThread.start();
+    ses = Executors.newSingleThreadScheduledExecutor(new ThreadFactory() {
+      public Thread newThread(Runnable r) {
+        Thread t = new Thread(r);
+        t.setName(getName());
+        return t;
+      }
+    });
+    handler = ses.scheduleAtFixedRate(new PreemptionChecker(),
+        0, monitorInterval, TimeUnit.MILLISECONDS);
     super.serviceStart();
   }
 
   @Override
   public void serviceStop() throws Exception {
     stopped = true;
-    if (checkerThread != null) {
-      checkerThread.interrupt();
+    if (handler != null) {
+      LOG.info("Stop " + getName());
+      handler.cancel(true);
+      ses.shutdown();
     }
     super.serviceStop();
   }
@@ -84,24 +99,12 @@ public class SchedulingMonitor extends AbstractService {
   private class PreemptionChecker implements Runnable {
     @Override
     public void run() {
-      while (!stopped && !Thread.currentThread().isInterrupted()) {
-        try {
-          //invoke the preemption policy at a regular pace
-          //the policy will generate preemption or kill events
-          //managed by the dispatcher
-          invokePolicy();
-        } catch (YarnRuntimeException e) {
-          LOG.error("YarnRuntimeException raised while executing preemption"
-              + " checker, skip this run..., exception=", e);
-        }
-
-        // Wait before next run
-        try {
-          Thread.sleep(monitorInterval);
-        } catch (InterruptedException e) {
-          LOG.info(getName() + " thread interrupted");
-          break;
-        }
+      try {
+        //invoke the preemption policy
+        invokePolicy();
+      } catch (YarnRuntimeException e) {
+        LOG.error("YarnRuntimeException raised while executing preemption"
+            + " checker, skip this run..., exception=", e);
       }
     }
   }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/test/java/org/apache/hadoop/yarn/server/resourcemanager/monitor/TestSchedulingMonitor.java

@@ -26,6 +26,7 @@ import org.apache.hadoop.yarn.server.resourcemanager.monitor.capacity.Proportion
 import org.junit.Test;
 
 import static org.junit.Assert.fail;
+import static org.mockito.Mockito.*;
 
 public class TestSchedulingMonitor {
 
@@ -43,5 +44,23 @@ public class TestSchedulingMonitor {
       fail("ResourceManager does not start when " +
           YarnConfiguration.RM_SCHEDULER_ENABLE_MONITORS + " is set to true");
     }
+
+    SchedulingEditPolicy mPolicy = mock(SchedulingEditPolicy.class);
+    when(mPolicy.getMonitoringInterval()).thenReturn(1000L);
+    SchedulingMonitor monitor = new SchedulingMonitor(rm.getRMContext(),
+        mPolicy);
+    try {
+      monitor.serviceInit(conf);
+      monitor.serviceStart();
+    } catch (Exception e) {
+      fail("SchedulingMonitor failes to start.");
+    }
+    verify(mPolicy, times(1)).editSchedule();
+    try {
+      monitor.close();
+      rm.close();
+    } catch (Exception e) {
+      fail("Failed to close.");
+    }
   }
 }