ClusterService implementation that relies on accrual failure detector for determ…

…ining node up/down status.
Initially off by default, until futher testing is done.

Change-Id: I0ac8850d76af717e7804d4503bedb227d5894a0a

@@ -32,6 +32,13 @@
     <description>ONOS Gossip based distributed store subsystems</description>
 
     <dependencies>
+
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>3.2</version>
+        </dependency>
+
         <dependency>
             <groupId>org.onosproject</groupId>
             <artifactId>onos-core-serializers</artifactId>

+package org.onosproject.store.cluster.impl;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Map;
+
+import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;
+import org.onosproject.cluster.NodeId;
+
+import com.google.common.collect.Maps;
+
+/**
+ * Phi Accrual failure detector.
+ * <p>
+ * Based on a paper titled: "The φ Accrual Failure Detector" by Hayashibara, et al.
+ */
+public class PhiAccrualFailureDetector {
+    private final Map<NodeId, History> states = Maps.newConcurrentMap();
+
+    // TODO: make these configurable.
+    private static final int WINDOW_SIZE = 250;
+    private static final int MIN_SAMPLES = 25;
+
+    // If a node does not have any heartbeats, this is the phi
+    // value to report. Indicates the node is inactive (from the
+    // detectors perspective.
+    private static final double BOOTSTRAP_PHI_VALUE = 100.0;
+
+    /**
+     * Report a new heart beat for the specified node id.
+     * @param nodeId node id
+     */
+    public void report(NodeId nodeId) {
+        report(nodeId, System.currentTimeMillis());
+    }
+
+    /**
+     * Report a new heart beat for the specified node id.
+     * @param nodeId node id
+     * @param arrivalTime arrival time
+     */
+    public void report(NodeId nodeId, long arrivalTime) {
+        checkNotNull(nodeId, "NodeId must not be null");
+        checkArgument(arrivalTime >= 0, "arrivalTime must not be negative");
+        History nodeState =
+                states.computeIfAbsent(nodeId, key -> new History());
+        synchronized (nodeState) {
+            long latestHeartbeat = nodeState.latestHeartbeatTime();
+            if (latestHeartbeat != -1) {
+                nodeState.samples().addValue(arrivalTime - latestHeartbeat);
+            }
+            nodeState.setLatestHeartbeatTime(arrivalTime);
+        }
+    }
+
+    /**
+     * Compute phi for the specified node id.
+     * @param nodeId node id
+     * @return phi value
+     */
+    public Double phi(NodeId nodeId) {
+        if (!states.containsKey(nodeId)) {
+            return BOOTSTRAP_PHI_VALUE;
+        }
+        checkNotNull(nodeId, "NodeId must not be null");
+        History nodeState = states.get(nodeId);
+        synchronized (nodeState) {
+            long latestHeartbeat = nodeState.latestHeartbeatTime();
+            DescriptiveStatistics samples = nodeState.samples();
+            if (latestHeartbeat == -1 || samples.getN() < MIN_SAMPLES) {
+                return 0.0;
+            }
+            return computePhi(samples, latestHeartbeat, System.currentTimeMillis());
+        }
+    }
+
+    private double computePhi(DescriptiveStatistics samples, long tLast, long tNow) {
+        long size = samples.getN();
+        long t = tNow - tLast;
+        return (size > 0)
+               ? (1.0 / Math.log(10.0)) * t / samples.getMean()
+               : BOOTSTRAP_PHI_VALUE;
+    }
+
+    private static class History {
+        DescriptiveStatistics samples =
+                new DescriptiveStatistics(WINDOW_SIZE);
+        long lastHeartbeatTime = -1;
+
+        public DescriptiveStatistics samples() {
+            return samples;
+        }
+
+        public long latestHeartbeatTime() {
+            return lastHeartbeatTime;
+        }
+
+        public void setLatestHeartbeatTime(long value) {
+            lastHeartbeatTime = value;
+        }
+    }
+}
\ No newline at end of file

@@ -33,6 +33,7 @@
         <bundle>mvn:io.netty/netty-codec/4.0.23.Final</bundle>
         <bundle>mvn:io.netty/netty-transport-native-epoll/4.0.23.Final</bundle>
         <bundle>mvn:commons-pool/commons-pool/1.6</bundle>
+        <bundle>mvn:org.apache.commons/commons-math3/3.2</bundle>
 
         <bundle>mvn:joda-time/joda-time/2.5</bundle>