/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.synapse.endpoints.algorithms;
import org.apache.axis2.clustering.Member;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.synapse.MessageContext;
import org.apache.synapse.endpoints.Endpoint;
import java.util.List;
/**
* This is the implementation of the round robin load balancing algorithm. It simply iterates
* through the endpoint list one by one for until an active endpoint is found.
*/
public class RoundRobin implements LoadbalanceAlgorithm {
private static final Log log = LogFactory.getLog(RoundRobin.class);
/**
* Endpoints list for the round robin algorithm
*/
private List endpoints = null;
private List<Member> members;
public RoundRobin() {
}
public RoundRobin(List endpoints) {
this.endpoints = endpoints;
}
public void setApplicationMembers(List<Member> members) {
this.members = members;
}
public void setEndpoints(List<Endpoint> endpoints) {
this.endpoints = endpoints;
}
public void setLoadBalanceEndpoint(Endpoint endpoint) {}
/**
* Choose an active endpoint using the round robin algorithm. If there are no active endpoints
* available, returns null.
*
* @param synCtx MessageContext instance which holds all per-message properties
* @param algorithmContext The context in which holds run time states related to the algorithm
* @return endpoint to send the next message
*/
public Endpoint getNextEndpoint(MessageContext synCtx, AlgorithmContext algorithmContext) {
Endpoint nextEndpoint;
int attempts = 0;
synchronized (algorithmContext) {
int currentEPR = algorithmContext.getCurrentEndpointIndex();
do {
// two successive clients could get the same endpoint if not synchronized.
nextEndpoint = (Endpoint) endpoints.get(currentEPR);
if (currentEPR == endpoints.size() - 1) {
currentEPR = 0;
} else {
currentEPR++;
}
algorithmContext.setCurrentEndpointIndex(currentEPR);
attempts++;
if (attempts > endpoints.size()) {
return null;
}
} while (!nextEndpoint.readyToSend());
}
return nextEndpoint;
}
public Member getNextApplicationMember(AlgorithmContext algorithmContext) {
if (members.size() == 0) {
return null;
}
Member current;
synchronized (algorithmContext) {
int currentMemberIndex = algorithmContext.getCurrentEndpointIndex();
if (currentMemberIndex >= members.size()) {
currentMemberIndex = 0;
}
current = members.get(currentMemberIndex);
if (currentMemberIndex == members.size() - 1) {
currentMemberIndex = 0;
} else {
currentMemberIndex++;
}
algorithmContext.setCurrentEndpointIndex(currentMemberIndex);
if (log.isDebugEnabled()) {
log.debug("Members : " + members.size());
log.debug("Current member: " + current);
}
}
return current;
}
public void reset(AlgorithmContext algorithmContext) {
if (log.isDebugEnabled()) {
log.debug("Resetting the Round Robin loadbalancing algorithm ...");
}
synchronized (algorithmContext) {
algorithmContext.setCurrentEndpointIndex(0);
}
}
public String getName() {
return "RoundRobin";
}
}