STORM-2874: Minor refactoring of some backpressure code

storm-client/src/jvm/org/apache/storm/daemon/worker/Worker.java

@@ -227,7 +227,7 @@ public void start() throws Exception {
                     .setLowWaterMark(ObjectReader.getDouble(topologyConf.get(Config.BACKPRESSURE_DISRUPTOR_LOW_WATERMARK)));
 
                 WorkerBackpressureCallback backpressureCallback = mkBackpressureHandler(topologyConf);
-                backpressureThread = new WorkerBackpressureThread(workerState.backpressureTrigger, workerState, backpressureCallback);
+                backpressureThread = new WorkerBackpressureThread(workerState.backpressureTrigger, backpressureCallback);
                 if ((Boolean) topologyConf.get(Config.TOPOLOGY_BACKPRESSURE_ENABLE)) {
                     backpressureThread.start();
                     stormClusterState.topologyBackpressure(topologyId, backpressureZnodeTimeoutMs, workerState::refreshThrottle);
@@ -408,7 +408,7 @@ private WorkerBackpressureCallback mkBackpressureHandler(Map<String, Object> top
         final List<IRunningExecutor> executors = executorsAtom.get();
         final long updateFreqMs = ObjectReader.getInt(topologyConf.get(Config.BACKPRESSURE_ZNODE_UPDATE_FREQ_SECS)) * 1000;
         return new WorkerBackpressureCallback() {
-            @Override public void onEvent(Object obj) {
+            @Override public void onEvent() {
                 if (null != executors) {
                     String topologyId = workerState.topologyId;
                     String assignmentId = workerState.assignmentId;
@@ -418,8 +418,9 @@ private WorkerBackpressureCallback mkBackpressureHandler(Map<String, Object> top
                     long currTimestamp = System.currentTimeMillis();
                     long currBackpressureTimestamp = 0;
                     // the backpressure flag is true if at least one of the disruptor queues has throttle-on
-                    boolean backpressureFlag = workerState.transferQueue.getThrottleOn() || (executors.stream()
-                            .map(IRunningExecutor::getBackPressureFlag).reduce((op1, op2) -> (op1 || op2)).get());
+                    boolean backpressureFlag = workerState.transferQueue.getThrottleOn() ||
+                        (executors.stream()
+                            .anyMatch(IRunningExecutor::getBackPressureFlag));
 
                     if (backpressureFlag) {
                         // update the backpressure timestamp every updateFreqMs ms

storm-client/src/jvm/org/apache/storm/utils/WorkerBackpressureCallback.java

@@ -21,6 +21,6 @@
 
 public interface WorkerBackpressureCallback {
 
-    void onEvent(Object obj);
+    void onEvent();
 
 }

storm-client/src/jvm/org/apache/storm/utils/WorkerBackpressureThread.java

@@ -21,17 +21,15 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public class WorkerBackpressureThread extends Thread {
+public final class WorkerBackpressureThread extends Thread {
 
     private static final Logger LOG = LoggerFactory.getLogger(WorkerBackpressureThread.class);
     private final Object trigger;
-    private final Object workerData;
     private final WorkerBackpressureCallback callback;
     private volatile boolean running = true;
 
-    public WorkerBackpressureThread(Object trigger, Object workerData, WorkerBackpressureCallback callback) {
+    public WorkerBackpressureThread(Object trigger, WorkerBackpressureCallback callback) {
         this.trigger = trigger;
-        this.workerData = workerData;
         this.callback = callback;
         this.setName("WorkerBackpressureThread");
         this.setDaemon(true);
@@ -60,21 +58,22 @@ public void run() {
                 synchronized (trigger) {
                     trigger.wait(100);
                 }
-                callback.onEvent(workerData); // check all executors and update zk backpressure throttle for the worker if needed
+                callback.onEvent(); // check all executors and update zk backpressure throttle for the worker if needed
             } catch (InterruptedException interEx) {
                 // ignored, we are shutting down.
             }
         }
     }
-}
 
-class BackpressureUncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
-    private static final Logger LOG = LoggerFactory.getLogger(BackpressureUncaughtExceptionHandler.class);
+    private static class BackpressureUncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
+
+        private static final Logger LOG = LoggerFactory.getLogger(BackpressureUncaughtExceptionHandler.class);
 
-    @Override
-    public void uncaughtException(Thread t, Throwable e) {
-        // note that exception that happens during connecting to ZK has been ignored in the callback implementation
-        LOG.error("Received error or exception in WorkerBackpressureThread.. terminating the worker...", e);
-        Runtime.getRuntime().exit(1);
+        @Override
+        public void uncaughtException(Thread t, Throwable e) {
+            // note that exception that happens during connecting to ZK has been ignored in the callback implementation
+            LOG.error("Received error or exception in WorkerBackpressureThread.. terminating the worker...", e);
+            Runtime.getRuntime().exit(1);
+        }
     }
 }

storm-client/test/jvm/org/apache/storm/utils/WorkerBackpressureThreadTest.java

@@ -18,33 +18,33 @@
 
 package org.apache.storm.utils;
 
-import java.util.concurrent.atomic.AtomicLong;
-import org.junit.Assert;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 import org.junit.Test;
-import junit.framework.TestCase;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public class WorkerBackpressureThreadTest extends TestCase {
+public class WorkerBackpressureThreadTest {
     private static final Logger LOG = LoggerFactory.getLogger(WorkerBackpressureThreadTest.class);
 
     @Test
     public void testNormalEvent() throws Exception {
+        CountDownLatch latch = new CountDownLatch(1);
         Object trigger = new Object();
-        AtomicLong workerData = new AtomicLong(0);
         WorkerBackpressureCallback callback = new WorkerBackpressureCallback() {
             @Override
-            public void onEvent(Object obj) {
-                ((AtomicLong) obj).getAndDecrement();
+            public void onEvent() {
+                latch.countDown();
             }
         };
-        WorkerBackpressureThread workerBackpressureThread = new WorkerBackpressureThread(trigger, workerData, callback);
+        WorkerBackpressureThread workerBackpressureThread = new WorkerBackpressureThread(trigger, callback);
         workerBackpressureThread.start();
         WorkerBackpressureThread.notifyBackpressureChecker(trigger);
-        long start = System.currentTimeMillis();
-        while (workerData.get() == 0) {
-            assertTrue("Timeout", (System.currentTimeMillis() - start) < 1000);
-            Thread.sleep(100);
-        }
+        //The callback should be called when the trigger is notified
+        assertThat(latch.await(1, TimeUnit.SECONDS), is(true));
     }
 }