HDFS-16139. Update BPServiceActor Scheduler's nextBlockReportTime atomically (#3228). Contributed by Viraj Jasani.

Signed-off-by: He Xiaoqiao <hexiaoqiao@apache.org>

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

@@ -39,6 +39,7 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.ha.HAServiceProtocol.HAServiceState;
@@ -323,10 +324,10 @@ class BPServiceActor implements Runnable {
   void triggerBlockReportForTests() {
     synchronized (ibrManager) {
       scheduler.scheduleHeartbeat();
-      long oldBlockReportTime = scheduler.nextBlockReportTime;
+      long oldBlockReportTime = scheduler.getNextBlockReportTime();
       scheduler.forceFullBlockReportNow();
       ibrManager.notifyAll();
-      while (oldBlockReportTime == scheduler.nextBlockReportTime) {
+      while (oldBlockReportTime == scheduler.getNextBlockReportTime()) {
         try {
           ibrManager.wait(100);
         } catch (InterruptedException e) {
@@ -1163,8 +1164,8 @@ class BPServiceActor implements Runnable {
     // nextBlockReportTime and nextHeartbeatTime may be assigned/read
     // by testing threads (through BPServiceActor#triggerXXX), while also
     // assigned/read by the actor thread.
-    @VisibleForTesting
-    volatile long nextBlockReportTime = monotonicNow();
+    private final AtomicLong nextBlockReportTime =
+        new AtomicLong(monotonicNow());
 
     @VisibleForTesting
     volatile long nextHeartbeatTime = monotonicNow();
@@ -1257,7 +1258,7 @@ class BPServiceActor implements Runnable {
     }
 
     boolean isBlockReportDue(long curTime) {
-      return nextBlockReportTime - curTime <= 0;
+      return nextBlockReportTime.get() - curTime <= 0;
     }
 
     boolean isOutliersReportDue(long curTime) {
@@ -1281,15 +1282,15 @@ class BPServiceActor implements Runnable {
     long scheduleBlockReport(long delay, boolean isRegistration) {
       if (delay > 0) { // send BR after random delay
         // Numerical overflow is possible here and is okay.
-        nextBlockReportTime =
-            monotonicNow() + ThreadLocalRandom.current().nextInt((int) (delay));
+        nextBlockReportTime.getAndSet(
+            monotonicNow() + ThreadLocalRandom.current().nextInt((int) (delay)));
       } else { // send at next heartbeat
-        nextBlockReportTime = monotonicNow();
+        nextBlockReportTime.getAndSet(monotonicNow());
       }
       resetBlockReportTime = isRegistration; // reset future BRs for
       // randomness, post first block report to avoid regular BRs from all
       // DN's coming at one time.
-      return nextBlockReportTime;
+      return nextBlockReportTime.get();
     }
 
     /**
@@ -1302,8 +1303,8 @@ class BPServiceActor implements Runnable {
       // If we have sent the first set of block reports, then wait a random
       // time before we start the periodic block reports.
       if (resetBlockReportTime) {
-        nextBlockReportTime = monotonicNow() +
-            ThreadLocalRandom.current().nextInt((int)(blockReportIntervalMs));
+        nextBlockReportTime.getAndSet(monotonicNow() +
+            ThreadLocalRandom.current().nextInt((int) (blockReportIntervalMs)));
         resetBlockReportTime = false;
       } else {
         /* say the last block report was at 8:20:14. The current report
@@ -1313,17 +1314,16 @@ class BPServiceActor implements Runnable {
          *   2) unexpected like 21:35:43, next report should be at 2:20:14
          *      on the next day.
          */
-        long factor =
-            (monotonicNow() - nextBlockReportTime + blockReportIntervalMs)
-                / blockReportIntervalMs;
+        long factor = (monotonicNow() - nextBlockReportTime.get()
+            + blockReportIntervalMs) / blockReportIntervalMs;
         if (factor != 0) {
-          nextBlockReportTime += factor * blockReportIntervalMs;
+          nextBlockReportTime.getAndAdd(factor * blockReportIntervalMs);
         } else {
           // If the difference between the present time and the scheduled
           // time is very less, the factor can be 0, so in that case, we can
           // ignore that negligible time, spent while sending the BRss and
           // schedule the next BR after the blockReportInterval.
-          nextBlockReportTime += blockReportIntervalMs;
+          nextBlockReportTime.getAndAdd(blockReportIntervalMs);
         }
       }
     }
@@ -1336,6 +1336,16 @@ class BPServiceActor implements Runnable {
       return nextLifelineTime - monotonicNow();
     }
 
+    @VisibleForTesting
+    long getNextBlockReportTime() {
+      return nextBlockReportTime.get();
+    }
+
+    @VisibleForTesting
+    void setNextBlockReportTime(long nextBlockReportTime) {
+      this.nextBlockReportTime.getAndSet(nextBlockReportTime);
+    }
+
     /**
      * Wrapped for testing.
      * @return

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

@@ -31,6 +31,7 @@ import java.util.Random;
 
 import static java.lang.Math.abs;
 import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
@@ -70,7 +71,7 @@ public class TestBpServiceActorScheduler {
       Scheduler scheduler = makeMockScheduler(now);
       scheduler.scheduleBlockReport(0, true);
       assertTrue(scheduler.resetBlockReportTime);
-      assertThat(scheduler.nextBlockReportTime, is(now));
+      assertThat(scheduler.getNextBlockReportTime(), is(now));
     }
   }
 
@@ -81,8 +82,8 @@ public class TestBpServiceActorScheduler {
       final long delayMs = 10;
       scheduler.scheduleBlockReport(delayMs, true);
       assertTrue(scheduler.resetBlockReportTime);
-      assertTrue(scheduler.nextBlockReportTime - now >= 0);
-      assertTrue(scheduler.nextBlockReportTime - (now + delayMs) < 0);
+      assertTrue(scheduler.getNextBlockReportTime() - now >= 0);
+      assertTrue(scheduler.getNextBlockReportTime() - (now + delayMs) < 0);
     }
   }
 
@@ -96,7 +97,8 @@ public class TestBpServiceActorScheduler {
       Scheduler scheduler = makeMockScheduler(now);
       assertTrue(scheduler.resetBlockReportTime);
       scheduler.scheduleNextBlockReport();
-      assertTrue(scheduler.nextBlockReportTime - (now + BLOCK_REPORT_INTERVAL_MS) < 0);
+      assertTrue(scheduler.getNextBlockReportTime()
+          - (now + BLOCK_REPORT_INTERVAL_MS) < 0);
     }
   }
 
@@ -110,7 +112,8 @@ public class TestBpServiceActorScheduler {
       Scheduler scheduler = makeMockScheduler(now);
       scheduler.resetBlockReportTime = false;
       scheduler.scheduleNextBlockReport();
-      assertThat(scheduler.nextBlockReportTime, is(now + BLOCK_REPORT_INTERVAL_MS));
+      assertThat(scheduler.getNextBlockReportTime(),
+          is(now + BLOCK_REPORT_INTERVAL_MS));
     }
   }
 
@@ -129,10 +132,12 @@ public class TestBpServiceActorScheduler {
       final long blockReportDelay =
           BLOCK_REPORT_INTERVAL_MS + random.nextInt(2 * (int) BLOCK_REPORT_INTERVAL_MS);
       final long origBlockReportTime = now - blockReportDelay;
-      scheduler.nextBlockReportTime = origBlockReportTime;
+      scheduler.setNextBlockReportTime(origBlockReportTime);
       scheduler.scheduleNextBlockReport();
-      assertTrue(scheduler.nextBlockReportTime - now < BLOCK_REPORT_INTERVAL_MS);
-      assertTrue(((scheduler.nextBlockReportTime - origBlockReportTime) % BLOCK_REPORT_INTERVAL_MS) == 0);
+      assertTrue((scheduler.getNextBlockReportTime() - now)
+          < BLOCK_REPORT_INTERVAL_MS);
+      assertEquals(0, ((scheduler.getNextBlockReportTime() - origBlockReportTime)
+          % BLOCK_REPORT_INTERVAL_MS));
     }
   }
 
@@ -201,7 +206,7 @@ public class TestBpServiceActorScheduler {
         HEARTBEAT_INTERVAL_MS, LIFELINE_INTERVAL_MS,
         BLOCK_REPORT_INTERVAL_MS, OUTLIER_REPORT_INTERVAL_MS));
     doReturn(now).when(mockScheduler).monotonicNow();
-    mockScheduler.nextBlockReportTime = now;
+    mockScheduler.setNextBlockReportTime(now);
     mockScheduler.nextHeartbeatTime = now;
     mockScheduler.nextOutliersReportTime = now;
     return mockScheduler;