HDDS-240. Implement metrics for EventQueue.

Contributed by Elek, Marton.

hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/server/events/EventQueue.java

@@ -18,7 +18,11 @@
 package org.apache.hadoop.hdds.server.events;
 
 import com.google.common.annotations.VisibleForTesting;
+
+import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
+
+import com.google.common.base.Preconditions;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -42,6 +46,8 @@ public class EventQueue implements EventPublisher, AutoCloseable {
   private static final Logger LOG =
       LoggerFactory.getLogger(EventQueue.class);
 
+  private static final String EXECUTOR_NAME_SEPARATOR = "For";
+
   private final Map<Event, Map<EventExecutor, List<EventHandler>>> executors =
       new HashMap<>();
 
@@ -51,38 +57,74 @@ public class EventQueue implements EventPublisher, AutoCloseable {
 
   public <PAYLOAD, EVENT_TYPE extends Event<PAYLOAD>> void addHandler(
       EVENT_TYPE event, EventHandler<PAYLOAD> handler) {
-
-    this.addHandler(event, new SingleThreadExecutor<>(
-        event.getName()), handler);
-  }
-
-  public <PAYLOAD, EVENT_TYPE extends Event<PAYLOAD>> void addHandler(
-      EVENT_TYPE event,
-      EventExecutor<PAYLOAD> executor,
-      EventHandler<PAYLOAD> handler) {
-
-    executors.putIfAbsent(event, new HashMap<>());
-    executors.get(event).putIfAbsent(executor, new ArrayList<>());
-
-    executors.get(event)
-        .get(executor)
-        .add(handler);
+    this.addHandler(event, handler, generateHandlerName(handler));
   }
 
   /**
-   * Creates one executor with multiple event handlers.
+   * Add new handler to the event queue.
+   * <p>
+   * By default a separated single thread executor will be dedicated to
+   * deliver the events to the registered event handler.
+   *
+   * @param event        Triggering event.
+   * @param handler      Handler of event (will be called from a separated
+   *                     thread)
+   * @param handlerName  The name of handler (should be unique together with
+   *                     the event name)
+   * @param <PAYLOAD>    The type of the event payload.
+   * @param <EVENT_TYPE> The type of the event identifier.
    */
-  public void addHandlerGroup(String name, HandlerForEvent<?>...
-      eventsAndHandlers) {
-    SingleThreadExecutor sharedExecutor =
-        new SingleThreadExecutor(name);
-    for (HandlerForEvent handlerForEvent : eventsAndHandlers) {
-      addHandler(handlerForEvent.event, sharedExecutor,
-          handlerForEvent.handler);
-    }
+  public <PAYLOAD, EVENT_TYPE extends Event<PAYLOAD>> void addHandler(
+      EVENT_TYPE event, EventHandler<PAYLOAD> handler, String handlerName) {
+    validateEvent(event);
+    Preconditions.checkNotNull(handler, "Handler name should not be null.");
+    String executorName =
+        StringUtils.camelize(event.getName()) + EXECUTOR_NAME_SEPARATOR
+            + handlerName;
+    this.addHandler(event, new SingleThreadExecutor<>(executorName), handler);
+  }
+
+  private <EVENT_TYPE extends Event<?>> void validateEvent(EVENT_TYPE event) {
+    Preconditions
+        .checkArgument(!event.getName().contains(EXECUTOR_NAME_SEPARATOR),
+            "Event name should not contain " + EXECUTOR_NAME_SEPARATOR
+                + " string.");
 
   }
 
+  private <PAYLOAD> String generateHandlerName(EventHandler<PAYLOAD> handler) {
+    if (!"".equals(handler.getClass().getSimpleName())) {
+      return handler.getClass().getSimpleName();
+    } else {
+      return handler.getClass().getName();
+    }
+  }
+
+  /**
+   * Add event handler with custom executor.
+   *
+   * @param event        Triggering event.
+   * @param executor     The executor imlementation to deliver events from a
+   *                     separated threads. Please keep in your mind that
+   *                     registering metrics is the responsibility of the
+   *                     caller.
+   * @param handler      Handler of event (will be called from a separated
+   *                     thread)
+   * @param <PAYLOAD>    The type of the event payload.
+   * @param <EVENT_TYPE> The type of the event identifier.
+   */
+  public <PAYLOAD, EVENT_TYPE extends Event<PAYLOAD>> void addHandler(
+      EVENT_TYPE event, EventExecutor<PAYLOAD> executor,
+      EventHandler<PAYLOAD> handler) {
+    validateEvent(event);
+    executors.putIfAbsent(event, new HashMap<>());
+    executors.get(event).putIfAbsent(executor, new ArrayList<>());
+
+    executors.get(event).get(executor).add(handler);
+  }
+
+
+
   /**
    * Route an event with payload to the right listener(s).
    *
@@ -183,31 +225,5 @@ public void close() {
     });
   }
 
-  /**
-   * Event identifier together with the handler.
-   *
-   * @param <PAYLOAD>
-   */
-  public static class HandlerForEvent<PAYLOAD> {
-
-    private final Event<PAYLOAD> event;
-
-    private final EventHandler<PAYLOAD> handler;
-
-    public HandlerForEvent(
-        Event<PAYLOAD> event,
-        EventHandler<PAYLOAD> handler) {
-      this.event = event;
-      this.handler = handler;
-    }
-
-    public Event<PAYLOAD> getEvent() {
-      return event;
-    }
-
-    public EventHandler<PAYLOAD> getHandler() {
-      return handler;
-    }
-  }
 
 }

hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/server/events/SingleThreadExecutor.java

@@ -23,13 +23,18 @@
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicLong;
+
+import org.apache.hadoop.metrics2.annotation.Metric;
+import org.apache.hadoop.metrics2.annotation.Metrics;
+import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
+import org.apache.hadoop.metrics2.lib.MutableCounterLong;
 
 /**
  * Simple EventExecutor to call all the event handler one-by-one.
  *
  * @param <T>
  */
+@Metrics(context = "EventQueue")
 public class SingleThreadExecutor<T> implements EventExecutor<T> {
 
   public static final String THREAD_NAME_PREFIX = "EventQueue";
@@ -41,14 +46,24 @@ public class SingleThreadExecutor<T> implements EventExecutor<T> {
 
   private final ThreadPoolExecutor executor;
 
-  private final AtomicLong queuedCount = new AtomicLong(0);
+  @Metric
+  private MutableCounterLong queued;
 
-  private final AtomicLong successfulCount = new AtomicLong(0);
+  @Metric
+  private MutableCounterLong done;
 
-  private final AtomicLong failedCount = new AtomicLong(0);
+  @Metric
+  private MutableCounterLong failed;
 
+  /**
+   * Create SingleThreadExecutor.
+   *
+   * @param name Unique name used in monitoring and metrics.
+   */
   public SingleThreadExecutor(String name) {
     this.name = name;
+    DefaultMetricsSystem.instance()
+        .register("EventQueue" + name, "Event Executor metrics ", this);
 
     LinkedBlockingQueue<Runnable> workQueue = new LinkedBlockingQueue<>();
     executor =
@@ -64,31 +79,31 @@ public SingleThreadExecutor(String name) {
   @Override
   public void onMessage(EventHandler<T> handler, T message, EventPublisher
       publisher) {
-    queuedCount.incrementAndGet();
+    queued.incr();
     executor.execute(() -> {
       try {
         handler.onMessage(message, publisher);
-        successfulCount.incrementAndGet();
+        done.incr();
       } catch (Exception ex) {
         LOG.error("Error on execution message {}", message, ex);
-        failedCount.incrementAndGet();
+        failed.incr();
       }
     });
   }
 
   @Override
   public long failedEvents() {
-    return failedCount.get();
+    return failed.value();
   }
 
   @Override
   public long successfulEvents() {
-    return successfulCount.get();
+    return done.value();
   }
 
   @Override
   public long queuedEvents() {
-    return queuedCount.get();
+    return queued.value();
   }
 
   @Override

hadoop-hdds/framework/src/test/java/org/apache/hadoop/hdds/server/events/TestEventQueue.java

@@ -25,6 +25,8 @@
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import org.apache.hadoop.metrics2.lib.DefaultMetricsSystem;
+
 /**
  * Testing the basic functionality of the event queue.
  */
@@ -44,11 +46,13 @@ public class TestEventQueue {
 
   @Before
   public void startEventQueue() {
+    DefaultMetricsSystem.initialize(getClass().getSimpleName());
     queue = new EventQueue();
   }
 
   @After
   public void stopEventQueue() {
+    DefaultMetricsSystem.shutdown();
     queue.close();
   }
 
@@ -79,35 +83,4 @@ public void multipleSubscriber() {
 
   }
 
-  @Test
-  public void handlerGroup() {
-    final long[] result = new long[2];
-    queue.addHandlerGroup(
-        "group",
-        new EventQueue.HandlerForEvent<>(EVENT3, (payload, publisher) ->
-            result[0] = payload),
-        new EventQueue.HandlerForEvent<>(EVENT4, (payload, publisher) ->
-            result[1] = payload)
-    );
-
-    queue.fireEvent(EVENT3, 23L);
-    queue.fireEvent(EVENT4, 42L);
-
-    queue.processAll(1000);
-
-    Assert.assertEquals(23, result[0]);
-    Assert.assertEquals(42, result[1]);
-
-    Set<String> eventQueueThreadNames =
-        Thread.getAllStackTraces().keySet()
-            .stream()
-            .filter(t -> t.getName().startsWith(SingleThreadExecutor
-                .THREAD_NAME_PREFIX))
-            .map(Thread::getName)
-            .collect(Collectors.toSet());
-    System.out.println(eventQueueThreadNames);
-    Assert.assertEquals(1, eventQueueThreadNames.size());
-
-  }
-
 }