Updated accumulator documentation and refactored names to remove the event heritage.

Change-Id: I2238ab1215281702e670a406fb901ba8a4ef85ce

-/*
- * Copyright 2014 Open Networking Laboratory
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.onosproject.event;
-
-import org.onlab.util.AbstractAccumulator;
-
-import java.util.Timer;
-
-/**
- * Base implementation of an event accumulator. It allows triggering based on
- * event inter-arrival time threshold, maximum batch life threshold and maximum
- * batch size.
- */
-public abstract class AbstractEventAccumulator
-        extends AbstractAccumulator<Event>
-        implements EventAccumulator {
-
-    /**
-     * Creates an event accumulator capable of triggering on the specified
-     * thresholds.
-     *
-     * @param timer          timer to use for scheduling check-points
-     * @param maxEvents      maximum number of events to accumulate before
-     *                       processing is triggered
-     * @param maxBatchMillis maximum number of millis allowed since the first
-     *                       event before processing is triggered
-     * @param maxIdleMillis  maximum number millis between events before
-     *                       processing is triggered
-     */
-    protected AbstractEventAccumulator(Timer timer, int maxEvents,
-                                       int maxBatchMillis, int maxIdleMillis) {
-        super(timer, maxEvents, maxBatchMillis, maxIdleMillis);
-    }
-}

-/*
- * Copyright 2014 Open Networking Laboratory
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.onosproject.event;
-
-import org.onlab.util.Accumulator;
-
-/**
- * Abstraction of an accumulator capable of collecting events and at some
- * point in time triggers processing of all previously accumulated events.
- */
-public interface EventAccumulator extends Accumulator<Event> {
-}

@@ -53,8 +53,8 @@ public class IntentAccumulator extends AbstractAccumulator<IntentData> {
     }
 
     @Override
-    public void processEvents(List<IntentData> ops) {
-        delegate.execute(reduce(ops));
+    public void processItems(List<IntentData> items) {
+        delegate.execute(reduce(items));
         // FIXME kick off the work
         //for (IntentData data : opMap.values()) {}
     }

@@ -16,7 +16,6 @@
 package org.onosproject.net.topology.impl;
 
 import com.google.common.collect.ImmutableList;
-
 import org.apache.felix.scr.annotations.Activate;
 import org.apache.felix.scr.annotations.Component;
 import org.apache.felix.scr.annotations.Deactivate;
@@ -25,9 +24,9 @@ import org.apache.felix.scr.annotations.Property;
 import org.apache.felix.scr.annotations.Reference;
 import org.apache.felix.scr.annotations.ReferenceCardinality;
 import org.apache.felix.scr.annotations.Service;
-import org.onosproject.event.AbstractEventAccumulator;
+import org.onlab.util.AbstractAccumulator;
+import org.onlab.util.Accumulator;
 import org.onosproject.event.Event;
-import org.onosproject.event.EventAccumulator;
 import org.onosproject.net.device.DeviceEvent;
 import org.onosproject.net.device.DeviceListener;
 import org.onosproject.net.device.DeviceService;
@@ -51,9 +50,9 @@ import java.util.concurrent.ExecutorService;
 
 import static com.google.common.base.Strings.isNullOrEmpty;
 import static java.util.concurrent.Executors.newFixedThreadPool;
+import static org.onlab.util.Tools.namedThreads;
 import static org.onosproject.core.CoreService.CORE_PROVIDER_ID;
 import static org.onosproject.net.device.DeviceEvent.Type.*;
-import static org.onlab.util.Tools.namedThreads;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
@@ -104,7 +103,7 @@ public class DefaultTopologyProvider extends AbstractProvider
     private DeviceListener deviceListener = new InternalDeviceListener();
     private LinkListener linkListener = new InternalLinkListener();
 
-    private EventAccumulator accumulator;
+    private Accumulator<Event> accumulator;
     private ExecutorService executor;
 
     /**
@@ -245,18 +244,15 @@ public class DefaultTopologyProvider extends AbstractProvider
     }
 
     // Event accumulator for paced triggering of topology assembly.
-    private class TopologyChangeAccumulator
-            extends AbstractEventAccumulator implements EventAccumulator {
-
+    private class TopologyChangeAccumulator extends AbstractAccumulator<Event> {
         TopologyChangeAccumulator() {
             super(TIMER, maxEvents, maxBatchMs, maxIdleMs);
         }
 
         @Override
-        public void processEvents(List<Event> events) {
-            triggerTopologyBuild(events);
+        public void processItems(List<Event> items) {
+            triggerTopologyBuild(items);
         }
-
     }
 
     // Task for building topology data in a separate thread.

@@ -27,64 +27,63 @@ import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
 
 /**
- * Base implementation of an event accumulator. It allows triggering based on
- * event inter-arrival time threshold, maximum batch life threshold and maximum
+ * Base implementation of an item accumulator. It allows triggering based on
+ * item inter-arrival time threshold, maximum batch life threshold and maximum
  * batch size.
  */
-// FIXME refactor the names here
 public abstract class AbstractAccumulator<T> implements Accumulator<T> {
 
     private Logger log = LoggerFactory.getLogger(AbstractAccumulator.class);
 
     private final Timer timer;
-    private final int maxEvents;
+    private final int maxItems;
     private final int maxBatchMillis;
     private final int maxIdleMillis;
 
     private TimerTask idleTask = new ProcessorTask();
     private TimerTask maxTask = new ProcessorTask();
 
-    private List<T> events = Lists.newArrayList();
+    private List<T> items = Lists.newArrayList();
 
     /**
-     * Creates an event accumulator capable of triggering on the specified
+     * Creates an item accumulator capable of triggering on the specified
      * thresholds.
      *
      * @param timer               timer to use for scheduling check-points
-     * @param maxEvents      maximum number of events to accumulate before
+     * @param maxItems            maximum number of items to accumulate before
      *                            processing is triggered
      * @param maxBatchMillis      maximum number of millis allowed since the first
-     *                       event before processing is triggered
-     * @param maxIdleMillis  maximum number millis between events before
+     *                            item before processing is triggered
+     * @param maxIdleMillis       maximum number millis between items before
      *                            processing is triggered
      */
-    protected AbstractAccumulator(Timer timer, int maxEvents,
+    protected AbstractAccumulator(Timer timer, int maxItems,
                                   int maxBatchMillis, int maxIdleMillis) {
         this.timer = checkNotNull(timer, "Timer cannot be null");
 
-        checkArgument(maxEvents > 1, "Maximum number of events must be > 1");
+        checkArgument(maxItems > 1, "Maximum number of items must be > 1");
         checkArgument(maxBatchMillis > 0, "Maximum millis must be positive");
         checkArgument(maxIdleMillis > 0, "Maximum idle millis must be positive");
 
-        this.maxEvents = maxEvents;
+        this.maxItems = maxItems;
         this.maxBatchMillis = maxBatchMillis;
         this.maxIdleMillis = maxIdleMillis;
     }
 
     @Override
-    public synchronized void add(T event) {
+    public synchronized void add(T item) {
         idleTask = cancelIfActive(idleTask);
-        events.add(checkNotNull(event, "Event cannot be null"));
+        items.add(checkNotNull(item, "Item cannot be null"));
 
-        // Did we hit the max event threshold?
-        if (events.size() == maxEvents) {
+        // Did we hit the max item threshold?
+        if (items.size() == maxItems) {
             maxTask = cancelIfActive(maxTask);
             schedule(1);
         } else {
-            // Otherwise, schedule idle task and if this is a first event
+            // Otherwise, schedule idle task and if this is a first item
             // also schedule the max batch age task.
             idleTask = schedule(maxIdleMillis);
-            if (events.size() == 1) {
+            if (items.size() == 1) {
                 maxTask = schedule(maxBatchMillis);
             }
         }
@@ -105,24 +104,24 @@ public abstract class AbstractAccumulator<T> implements Accumulator<T> {
         return task;
     }
 
-    // Task for triggering processing of accumulated events
+    // Task for triggering processing of accumulated items
     private class ProcessorTask extends TimerTask {
         @Override
         public void run() {
             try {
                 idleTask = cancelIfActive(idleTask);
                 maxTask = cancelIfActive(maxTask);
-                processEvents(finalizeCurrentBatch());
+                processItems(finalizeCurrentBatch());
             } catch (Exception e) {
                 log.warn("Unable to process batch due to {}", e);
             }
         }
     }
 
-    // Demotes and returns the current batch of events and promotes a new one.
+    // Demotes and returns the current batch of items and promotes a new one.
     private synchronized List<T> finalizeCurrentBatch() {
-        List<T> toBeProcessed = events;
-        events = Lists.newArrayList();
+        List<T> toBeProcessed = items;
+        items = Lists.newArrayList();
         return toBeProcessed;
     }
 
@@ -136,18 +135,18 @@ public abstract class AbstractAccumulator<T> implements Accumulator<T> {
     }
 
     /**
-     * Returns the maximum number of events allowed to accumulate before
+     * Returns the maximum number of items allowed to accumulate before
      * processing is triggered.
      *
-     * @return max number of events
+     * @return max number of items
      */
-    public int maxEvents() {
-        return maxEvents;
+    public int maxItems() {
+        return maxItems;
     }
 
     /**
      * Returns the maximum number of millis allowed to expire since the first
-     * event before processing is triggered.
+     * item before processing is triggered.
      *
      * @return max number of millis a batch is allowed to last
      */
@@ -157,9 +156,9 @@ public abstract class AbstractAccumulator<T> implements Accumulator<T> {
 
     /**
      * Returns the maximum number of millis allowed to expire since the last
-     * event arrival before processing is triggered.
+     * item arrival before processing is triggered.
      *
-     * @return max number of millis since the last event
+     * @return max number of millis since the last item
      */
     public int maxIdleMillis() {
         return maxIdleMillis;

@@ -18,25 +18,28 @@ package org.onlab.util;
 import java.util.List;
 
 /**
- * Abstraction of an accumulator capable of collecting events and at some
- * point in time triggers processing of all previously accumulated events.
+ * Abstraction of an accumulator capable of collecting items and at some
+ * point in time triggers processing of all previously accumulated items.
+ *
+ * @param <T> item type
  */
 public interface Accumulator<T> {
 
     /**
-     * Adds an event to the current batch. This operation may, or may not
-     * trigger processing of the current batch of events.
+     * Adds an item to the current batch. This operation may, or may not
+     * trigger processing of the current batch of items.
      *
-     * @param event event to be added to the current batch
+     * @param item item to be added to the current batch
      */
-    void add(T event);
+    void add(T item);
 
     /**
-     * Processes the specified list of accumulated events.
+     * Processes the specified list of accumulated items.
      *
-     * @param events list of accumulated events
+     * @param items list of accumulated items
      */
-    void processEvents(List<T> events);
+    void processItems(List<T> items);
 
     //TODO consider a blocking version that required consumer participation
+
 }

 /*
- * Copyright 2014 Open Networking Laboratory
+ * Copyright 2015 Open Networking Laboratory
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package org.onosproject.event;
+package org.onlab.util;
 
 import org.junit.Ignore;
 import org.junit.Test;
@@ -21,16 +21,13 @@ import org.junit.Test;
 import java.util.List;
 import java.util.Timer;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.*;
 import static org.onlab.junit.TestTools.delay;
-import static org.onosproject.event.TestEvent.Type.FOO;
 
 /**
  * Tests the operation of the accumulator.
  */
-public class AbstractEventAccumulatorTest {
+public class AbstractAccumulatorTest {
 
     private final Timer timer = new Timer();
 
@@ -38,7 +35,7 @@ public class AbstractEventAccumulatorTest {
     public void basics() throws Exception {
         TestAccumulator accumulator = new TestAccumulator();
         assertEquals("incorrect timer", timer, accumulator.timer());
-        assertEquals("incorrect max events", 5, accumulator.maxEvents());
+        assertEquals("incorrect max events", 5, accumulator.maxItems());
         assertEquals("incorrect max ms", 100, accumulator.maxBatchMillis());
         assertEquals("incorrect idle ms", 50, accumulator.maxIdleMillis());
     }
@@ -46,12 +43,12 @@ public class AbstractEventAccumulatorTest {
     @Test
     public void eventTrigger() {
         TestAccumulator accumulator = new TestAccumulator();
-        accumulator.add(new TestEvent(FOO, "a"));
-        accumulator.add(new TestEvent(FOO, "b"));
-        accumulator.add(new TestEvent(FOO, "c"));
-        accumulator.add(new TestEvent(FOO, "d"));
+        accumulator.add(new TestItem("a"));
+        accumulator.add(new TestItem("b"));
+        accumulator.add(new TestItem("c"));
+        accumulator.add(new TestItem("d"));
         assertTrue("should not have fired yet", accumulator.batch.isEmpty());
-        accumulator.add(new TestEvent(FOO, "e"));
+        accumulator.add(new TestItem("e"));
         delay(20);
         assertFalse("should have fired", accumulator.batch.isEmpty());
         assertEquals("incorrect batch", "abcde", accumulator.batch);
@@ -61,16 +58,16 @@ public class AbstractEventAccumulatorTest {
     @Test
     public void timeTrigger() {
         TestAccumulator accumulator = new TestAccumulator();
-        accumulator.add(new TestEvent(FOO, "a"));
+        accumulator.add(new TestItem("a"));
         delay(30);
         assertTrue("should not have fired yet", accumulator.batch.isEmpty());
-        accumulator.add(new TestEvent(FOO, "b"));
+        accumulator.add(new TestItem("b"));
         delay(30);
         assertTrue("should not have fired yet", accumulator.batch.isEmpty());
-        accumulator.add(new TestEvent(FOO, "c"));
+        accumulator.add(new TestItem("c"));
         delay(30);
         assertTrue("should not have fired yet", accumulator.batch.isEmpty());
-        accumulator.add(new TestEvent(FOO, "d"));
+        accumulator.add(new TestItem("d"));
         delay(30);
         assertFalse("should have fired", accumulator.batch.isEmpty());
         assertEquals("incorrect batch", "abcd", accumulator.batch);
@@ -79,15 +76,23 @@ public class AbstractEventAccumulatorTest {
     @Test
     public void idleTrigger() {
         TestAccumulator accumulator = new TestAccumulator();
-        accumulator.add(new TestEvent(FOO, "a"));
+        accumulator.add(new TestItem("a"));
         assertTrue("should not have fired yet", accumulator.batch.isEmpty());
-        accumulator.add(new TestEvent(FOO, "b"));
+        accumulator.add(new TestItem("b"));
         delay(80);
         assertFalse("should have fired", accumulator.batch.isEmpty());
         assertEquals("incorrect batch", "ab", accumulator.batch);
     }
 
-    private class TestAccumulator extends AbstractEventAccumulator {
+    private class TestItem {
+        private final String s;
+
+        public TestItem(String s) {
+            this.s = s;
+        }
+    }
+
+    private class TestAccumulator extends AbstractAccumulator<TestItem> {
 
         String batch = "";
 
@@ -96,10 +101,11 @@ public class AbstractEventAccumulatorTest {
         }
 
         @Override
-        public void processEvents(List<Event> events) {
-            for (Event event : events) {
-                batch += event.subject();
+        public void processItems(List<TestItem> items) {
+            for (TestItem item : items) {
+                batch += item.s;
             }
         }
     }
+
 }

@@ -20,14 +20,14 @@ import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.ObjectNode;
 import org.eclipse.jetty.websocket.WebSocket;
 import org.onlab.osgi.ServiceDirectory;
+import org.onlab.util.AbstractAccumulator;
+import org.onlab.util.Accumulator;
 import org.onosproject.cluster.ClusterEvent;
 import org.onosproject.cluster.ClusterEventListener;
 import org.onosproject.cluster.ControllerNode;
 import org.onosproject.core.ApplicationId;
 import org.onosproject.core.CoreService;
-import org.onosproject.event.AbstractEventAccumulator;
 import org.onosproject.event.Event;
-import org.onosproject.event.EventAccumulator;
 import org.onosproject.mastership.MastershipAdminService;
 import org.onosproject.mastership.MastershipEvent;
 import org.onosproject.mastership.MastershipListener;
@@ -120,7 +120,7 @@ public class TopologyViewWebSocket
     private final IntentListener intentListener = new InternalIntentListener();
     private final FlowRuleListener flowListener = new InternalFlowListener();
 
-    private final EventAccumulator eventAccummulator = new InternalEventAccummulator();
+    private final Accumulator<Event> eventAccummulator = new InternalEventAccummulator();
 
     private TimerTask trafficTask;
     private ObjectNode trafficEvent;
@@ -721,13 +721,13 @@ public class TopologyViewWebSocket
     }
 
     // Accumulates events to drive methodic update of the summary pane.
-    private class InternalEventAccummulator extends AbstractEventAccumulator {
+    private class InternalEventAccummulator extends AbstractAccumulator<Event> {
         protected InternalEventAccummulator() {
             super(new Timer("topo-summary"), MAX_EVENTS, MAX_BATCH_MS, MAX_IDLE_MS);
         }
 
         @Override
-        public void processEvents(List<Event> events) {
+        public void processItems(List<Event> items) {
             try {
                 if (summaryEvent != null) {
                     sendMessage(summmaryMessage(0));