Don't run anti-entropy when under high load

Change-Id: I9e480708b9eced73da98e5c4cb27a18aeb08f09a

@@ -19,6 +19,7 @@ import org.apache.commons.lang3.RandomUtils;
 import org.apache.commons.lang3.mutable.MutableBoolean;
 import org.apache.commons.lang3.tuple.Pair;
 import org.onlab.util.KryoNamespace;
+import org.onlab.util.SlidingWindowCounter;
 import org.onosproject.cluster.ClusterService;
 import org.onosproject.cluster.ControllerNode;
 import org.onosproject.cluster.NodeId;
@@ -49,6 +50,7 @@ import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.stream.Collectors;
 
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -100,6 +102,12 @@ public class EventuallyConsistentMapImpl<K, V>
     private long periodSec = 5;
     private boolean lightweightAntiEntropy = true;
 
+    private static final int WINDOW_SIZE = 5;
+    private static final int HIGH_LOAD_THRESHOLD = 0;
+    private static final int LOAD_WINDOW = 2;
+    SlidingWindowCounter counter = new SlidingWindowCounter(WINDOW_SIZE);
+    AtomicLong operations = new AtomicLong();
+
     /**
      * Creates a new eventually consistent map shared amongst multiple instances.
      * <p>
@@ -271,6 +279,7 @@ public class EventuallyConsistentMapImpl<K, V>
     }
 
     private boolean putInternal(K key, V value, Timestamp timestamp) {
+        counter.incrementCount();
         Timestamp removed = removedItems.get(key);
         if (removed != null && removed.isNewerThan(timestamp)) {
             log.debug("ecmap - removed was newer {}", value);
@@ -318,6 +327,7 @@ public class EventuallyConsistentMapImpl<K, V>
     }
 
     private boolean removeInternal(K key, Timestamp timestamp) {
+        counter.incrementCount();
         final MutableBoolean updated = new MutableBoolean(false);
 
         items.compute(key, (k, existing) -> {
@@ -515,6 +525,10 @@ public class EventuallyConsistentMapImpl<K, V>
         clusterCommunicator.unicast(message, peer);
     }
 
+    private boolean underHighLoad() {
+        return counter.get(LOAD_WINDOW) > HIGH_LOAD_THRESHOLD;
+    }
+
     private final class SendAdvertisementTask implements Runnable {
         @Override
         public void run() {
@@ -523,6 +537,10 @@ public class EventuallyConsistentMapImpl<K, V>
                 return;
             }
 
+            if (underHighLoad()) {
+                return;
+            }
+
             try {
                 final NodeId self = clusterService.getLocalNode().id();
                 Set<ControllerNode> nodes = clusterService.getNodes();
@@ -745,7 +763,9 @@ public class EventuallyConsistentMapImpl<K, V>
                       message.sender());
             AntiEntropyAdvertisement<K> advertisement = serializer.decode(message.payload());
             try {
+                if (!underHighLoad()) {
                     handleAntiEntropyAdvertisement(advertisement);
+                }
             } catch (Exception e) {
                 log.warn("Exception thrown handling advertisements", e);
             }

+/*
+ * 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.
+ * 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.onlab.util;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.stream.Collectors;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * Maintains a sliding window of value counts. The sliding window counter is
+ * initialized with a number of window slots. Calls to #incrementCount() will
+ * increment the value in the current window slot. Periodically the window
+ * slides and the oldest value count is dropped. Calls to #get() will get the
+ * total count for the last N window slots.
+ */
+public final class SlidingWindowCounter {
+
+    private volatile int headSlot;
+    private final int windowSlots;
+
+    private final List<AtomicLong> counters;
+
+    private final ScheduledExecutorService background;
+
+    private static final int SLIDE_WINDOW_PERIOD_SECONDS = 1;
+
+    /**
+     * Creates a new sliding window counter with the given total number of
+     * window slots.
+     *
+     * @param windowSlots total number of window slots
+     */
+    public SlidingWindowCounter(int windowSlots) {
+        checkArgument(windowSlots > 0, "Window size must be a positive integer");
+
+        this.windowSlots = windowSlots;
+        this.headSlot = 0;
+
+        // Initialize each item in the list to an AtomicLong of 0
+        this.counters = Collections.nCopies(windowSlots, 0)
+                    .stream()
+                    .map(AtomicLong::new)
+                    .collect(Collectors.toCollection(ArrayList::new));
+
+        background = Executors.newSingleThreadScheduledExecutor();
+        background.scheduleWithFixedDelay(this::advanceHead, 0,
+                SLIDE_WINDOW_PERIOD_SECONDS, TimeUnit.SECONDS);
+    }
+
+    /**
+     * Releases resources used by the SlidingWindowCounter.
+     */
+    public void destroy() {
+        background.shutdownNow();
+    }
+
+    /**
+     * Increments the count of the current window slot by 1.
+     */
+    public void incrementCount() {
+        incrementCount(headSlot, 1);
+    }
+
+    /**
+     * Increments the count of the current window slot by the given value.
+     *
+     * @param value value to increment by
+     */
+    public void incrementCount(long value) {
+        incrementCount(headSlot, value);
+    }
+
+    private void incrementCount(int slot, long value) {
+        counters.get(slot).addAndGet(value);
+    }
+
+    /**
+     * Gets the total count for the last N window slots.
+     *
+     * @param slots number of slots to include in the count
+     * @return total count for last N slots
+     */
+    public long get(int slots) {
+        checkArgument(slots <= windowSlots,
+                      "Requested window must be less than the total window slots");
+
+        long sum = 0;
+
+        for (int i = 0; i < slots; i++) {
+            int currentIndex = headSlot - i;
+            if (currentIndex < 0) {
+                currentIndex = counters.size() + currentIndex;
+            }
+            sum += counters.get(currentIndex).get();
+        }
+
+        return sum;
+    }
+
+    void advanceHead() {
+        counters.get(slotAfter(headSlot)).set(0);
+        headSlot = slotAfter(headSlot);
+    }
+
+    private int slotAfter(int slot) {
+        return (slot + 1) % windowSlots;
+    }
+
+}

+/*
+ * 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.
+ * 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.onlab.util;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import static junit.framework.TestCase.fail;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Unit tests for the sliding window counter.
+ */
+public class SlidingWindowCounterTest {
+
+    private SlidingWindowCounter counter;
+
+    @Before
+    public void setUp() {
+        counter = new SlidingWindowCounter(2);
+    }
+
+    @After
+    public void tearDown() {
+        counter.destroy();
+    }
+
+    @Test
+    public void testIncrementCount() {
+        assertEquals(0, counter.get(1));
+        assertEquals(0, counter.get(2));
+        counter.incrementCount();
+        assertEquals(1, counter.get(1));
+        assertEquals(1, counter.get(2));
+        counter.incrementCount(2);
+        assertEquals(3, counter.get(2));
+    }
+
+    @Test
+    public void testSlide() {
+        counter.incrementCount();
+        counter.advanceHead();
+        assertEquals(0, counter.get(1));
+        assertEquals(1, counter.get(2));
+        counter.incrementCount(2);
+        assertEquals(2, counter.get(1));
+        assertEquals(3, counter.get(2));
+    }
+
+    @Test
+    public void testWrap() {
+        counter.incrementCount();
+        counter.advanceHead();
+        counter.incrementCount(2);
+        counter.advanceHead();
+        assertEquals(0, counter.get(1));
+        assertEquals(2, counter.get(2));
+        counter.advanceHead();
+        assertEquals(0, counter.get(1));
+        assertEquals(0, counter.get(2));
+
+    }
+
+    @Test
+    public void testCornerCases() {
+        try {
+            counter.get(3);
+            fail("Exception should have been thrown");
+        } catch (IllegalArgumentException e) {
+            assertTrue(true);
+        }
+
+        try {
+            new SlidingWindowCounter(0);
+            fail("Exception should have been thrown");
+        } catch (IllegalArgumentException e) {
+            assertTrue(true);
+        }
+
+        try {
+            new SlidingWindowCounter(-1);
+            fail("Exception should have been thrown");
+        } catch (IllegalArgumentException e) {
+            assertTrue(true);
+        }
+    }
+}