/* * 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.servicecomb.loadbalance; import java.util.List; import org.apache.servicecomb.core.Invocation; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.netflix.loadbalancer.LoadBalancerStats; import com.netflix.loadbalancer.ServerStats; /** * 会话保持策略:优先选择上一次选中的服务器,保证请求都发送到同一个服务器上去。 * 提供当会话过期或者失败次数超过限制后,轮询选择其他服务器的能力。 * */ public class SessionStickinessRule implements RuleExt { private static final Logger LOG = LoggerFactory.getLogger(SessionStickinessRule.class); private final Object lock = new Object(); private LoadBalancer loadBalancer; // use random rule as the trigger rule, to prevent consumer instance select the same producer instance. private RuleExt triggerRule; private volatile ServiceCombServer lastServer = null; private long lastAccessedTime = 0; private volatile boolean errorThresholdMet = false; private static final int MILLI_COUNT_IN_SECOND = 1000; private String microserviceName; public SessionStickinessRule() { triggerRule = new RoundRobinRuleExt(); } public void setLoadBalancer(LoadBalancer loadBalancer) { this.microserviceName = loadBalancer.getMicroServiceName(); this.loadBalancer = loadBalancer; } private ServiceCombServer chooseNextServer(List<ServiceCombServer> servers, Invocation invocation) { lastServer = triggerRule.choose(servers, invocation); lastAccessedTime = System.currentTimeMillis(); return lastServer; } private ServiceCombServer chooseInitialServer(List<ServiceCombServer> servers, Invocation invocation) { synchronized (lock) { if (lastServer == null) { chooseNextServer(servers, invocation); } } return lastServer; } private ServiceCombServer chooseServerWhenTimeout(List<ServiceCombServer> servers, Invocation invocation) { synchronized (lock) { if (isTimeOut()) { chooseNextServer(servers, invocation); } } return lastServer; } private ServiceCombServer chooseServerErrorThresholdMet(List<ServiceCombServer> servers, Invocation invocation) { synchronized (lock) { if (errorThresholdMet) { chooseNextServer(servers, invocation); errorThresholdMet = false; } } return lastServer; } private boolean isTimeOut() { return Configuration.INSTANCE.getSessionTimeoutInSeconds(microserviceName) > 0 && System.currentTimeMillis() - this.lastAccessedTime > ((long) Configuration.INSTANCE.getSessionTimeoutInSeconds(microserviceName) * MILLI_COUNT_IN_SECOND); } private boolean isErrorThresholdMet() { LoadBalancerStats stats = loadBalancer.getLoadBalancerStats(); if (stats != null && stats.getServerStats() != null && stats.getServerStats().size() > 0) { ServerStats serverStats = stats.getSingleServerStat(lastServer); int successiveFaildCount = serverStats.getSuccessiveConnectionFailureCount(); if (Configuration.INSTANCE.getSuccessiveFailedTimes(microserviceName) > 0 && successiveFaildCount >= Configuration.INSTANCE.getSuccessiveFailedTimes(microserviceName)) { serverStats.clearSuccessiveConnectionFailureCount(); return true; } } return false; } @Override public ServiceCombServer choose(List<ServiceCombServer> servers, Invocation invocation) { if (lastServer == null) { return chooseInitialServer(servers, invocation); } if (isTimeOut()) { LOG.warn("session timeout. choose another server."); return chooseServerWhenTimeout(servers, invocation); } else { this.lastAccessedTime = System.currentTimeMillis(); } if (isErrorThresholdMet()) { LOG.warn("reached max error. choose another server."); errorThresholdMet = true; return chooseServerErrorThresholdMet(servers, invocation); } if (!servers.contains(lastServer)) { return chooseNextServer(servers, invocation); } return lastServer; } }