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/*
* 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.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;
private static final double PHI_FACTOR = 1.0 / Math.log(10.0);
// 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) {
checkNotNull(nodeId, "NodeId must not be null");
if (!states.containsKey(nodeId)) {
return BOOTSTRAP_PHI_VALUE;
}
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)
? PHI_FACTOR * 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;
}
}
}
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