Ribbon負(fù)載均衡的策略有下面幾種：

上面我們講解了Ribbon的默認(rèn)輪詢負(fù)載均衡的算法

我們先看下Ribbon負(fù)載均衡的算法源碼：https://github.com/Netflix/ribbon/tree/master/ribbon-loadbalancer/src/main/java/com/netflix/loadbalancer? （Github上的源碼下載）

Ribbon負(fù)載均衡策略接口的源碼分析：

/* * * Copyright 2013 Netflix, Inc. * * 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 com.netflix.loadbalancer;/*** Interface that defines a "Rule" for a LoadBalancer. A Rule can be thought of* as a Strategy for loadbalacing. Well known loadbalancing strategies include* Round Robin, Response Time based etc.* * @author stonse* */ public interface IRule{/** choose one alive server from lb.allServers or* lb.upServers according to key* * @return choosen Server object. NULL is returned if none* server is available */public Server choose(Object key);public void setLoadBalancer(ILoadBalancer lb);public ILoadBalancer getLoadBalancer(); }

下面就看下是應(yīng)該用什么策略來(lái)設(shè)置負(fù)載均衡先看下抽象類測(cè)負(fù)載均衡策略類

/* * * Copyright 2013 Netflix, Inc. * * 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 com.netflix.loadbalancer;import com.netflix.client.IClientConfigAware;/*** Class that provides a default implementation for setting and getting load balancer* @author stonse**/ public abstract class AbstractLoadBalancerRule implements IRule, IClientConfigAware {private ILoadBalancer lb;@Overridepublic void setLoadBalancer(ILoadBalancer lb){this.lb = lb;}@Overridepublic ILoadBalancer getLoadBalancer(){return lb;} }

getLoadBalancer();返回負(fù)載均衡器，具體的負(fù)載均衡器由具體的實(shí)現(xiàn)類繼承得到

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下面我們看下負(fù)載均衡輪詢策略是怎么定義的（RoundRobinRule源碼分析）

/*** Copyright 2013 Netflix, Inc.** 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 com.netflix.loadbalancer;import com.netflix.client.config.IClientConfig; import org.slf4j.Logger; import org.slf4j.LoggerFactory;import java.util.List; import java.util.concurrent.atomic.AtomicInteger;/*** The most well known and basic load balancing strategy, i.e. Round Robin Rule.** @author stonse* @author Nikos Michalakis <nikos@netflix.com>**/ public class RoundRobinRule extends AbstractLoadBalancerRule {private AtomicInteger nextServerCyclicCounter;private static final boolean AVAILABLE_ONLY_SERVERS = true;private static final boolean ALL_SERVERS = false;private static Logger log = LoggerFactory.getLogger(RoundRobinRule.class);public RoundRobinRule() {nextServerCyclicCounter = new AtomicInteger(0);}public RoundRobinRule(ILoadBalancer lb) {this();setLoadBalancer(lb);}public Server choose(ILoadBalancer lb, Object key) {if (lb == null) {log.warn("no load balancer");return null;}Server server = null;int count = 0;while (server == null && count++ < 10) {List<Server> reachableServers = lb.getReachableServers();List<Server> allServers = lb.getAllServers();int upCount = reachableServers.size();int serverCount = allServers.size();if ((upCount == 0) || (serverCount == 0)) {log.warn("No up servers available from load balancer: " + lb);return null;}int nextServerIndex = incrementAndGetModulo(serverCount);server = allServers.get(nextServerIndex);if (server == null) {/* Transient. */Thread.yield();continue;}if (server.isAlive() && (server.isReadyToServe())) {return (server);}// Next.server = null;}if (count >= 10) {log.warn("No available alive servers after 10 tries from load balancer: "+ lb);}return server;}/*** Inspired by the implementation of {@link AtomicInteger#incrementAndGet()}.** @param modulo The modulo to bound the value of the counter.* @return The next value.*/private int incrementAndGetModulo(int modulo) {for (;;) {int current = nextServerCyclicCounter.get();int next = (current + 1) % modulo;if (nextServerCyclicCounter.compareAndSet(current, next))return next;}}@Overridepublic Server choose(Object key) {return choose(getLoadBalancer(), key);}@Overridepublic void initWithNiwsConfig(IClientConfig clientConfig) {} }

RoundRobinRule類通過(guò)繼承了AbstractLoadBalancerRule抽象類

就這樣實(shí)現(xiàn)了輪詢

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有源碼可以知道

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下面我在看下ILoadBalancer接口是怎么設(shè)置負(fù)載均衡器的（源碼分析）

/* * * Copyright 2013 Netflix, Inc. * * 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 com.netflix.loadbalancer;import java.util.List;/*** Interface that defines the operations for a software loadbalancer. A typical* loadbalancer minimally need a set of servers to loadbalance for, a method to* mark a particular server to be out of rotation and a call that will choose a* server from the existing list of server.* * @author stonse* */ public interface ILoadBalancer {/*** Initial list of servers.* This API also serves to add additional ones at a later time* The same logical server (host:port) could essentially be added multiple times* (helpful in cases where you want to give more "weightage" perhaps ..)* * @param newServers new servers to add*/public void addServers(List<Server> newServers);/*** Choose a server from load balancer.* * @param key An object that the load balancer may use to determine which server to return. null if * the load balancer does not use this parameter.* @return server chosen*/public Server chooseServer(Object key);/*** To be called by the clients of the load balancer to notify that a Server is down* else, the LB will think its still Alive until the next Ping cycle - potentially* (assuming that the LB Impl does a ping)* * @param server Server to mark as down*/public void markServerDown(Server server);/*** @deprecated 2016-01-20 This method is deprecated in favor of the* cleaner {@link #getReachableServers} (equivalent to availableOnly=true)* and {@link #getAllServers} API (equivalent to availableOnly=false).** Get the current list of servers.** @param availableOnly if true, only live and available servers should be returned*/@Deprecatedpublic List<Server> getServerList(boolean availableOnly);/*** @return Only the servers that are up and reachable.*/public List<Server> getReachableServers();/*** @return All known servers, both reachable and unreachable.*/public List<Server> getAllServers(); }

我可以看到這個(gè)負(fù)載均衡器的接口有下面四個(gè)實(shí)現(xiàn)類：

其中有一個(gè)抽象類負(fù)載均衡器AbstractLoadBalancer /* * * Copyright 2013 Netflix, Inc. * * 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 com.netflix.loadbalancer;import java.util.List;/*** AbstractLoadBalancer contains features required for most loadbalancing* implementations.* * An anatomy of a typical LoadBalancer consists of 1. A List of Servers (nodes)* that are potentially bucketed based on a specific criteria. 2. A Class that* defines and implements a LoadBalacing Strategy via <code>IRule</code> 3. A* Class that defines and implements a mechanism to determine the* suitability/availability of the nodes/servers in the List.* * * @author stonse* */ public abstract class AbstractLoadBalancer implements ILoadBalancer {public enum ServerGroup{ALL,STATUS_UP,STATUS_NOT_UP }/*** delegate to {@link #chooseServer(Object)} with parameter null.*/public Server chooseServer() {return chooseServer(null);}/*** List of servers that this Loadbalancer knows about* * @param serverGroup Servers grouped by status, e.g., {@link ServerGroup#STATUS_UP}*/public abstract List<Server> getServerList(ServerGroup serverGroup);/*** Obtain LoadBalancer related Statistics*/public abstract LoadBalancerStats getLoadBalancerStats(); }

選擇一個(gè)服務(wù)

裝載

下面我看下具體是怎么選擇的一個(gè)抽象類肯定會(huì)有很多是實(shí)現(xiàn)類其中一個(gè)是BaseLoadBalancer繼承AbstractLoadBalancer

有代碼可以知道new了一個(gè)輪詢的策略對(duì)象，默認(rèn)使用輪詢的策略做負(fù)載均衡

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當(dāng)然我們還可以看本地maven倉(cāng)庫(kù)的Ribbon源碼

但是Ribbon還提供了其他負(fù)載均衡的算法，當(dāng)我們程序顯式的聲明了其他負(fù)載均衡的算法，默認(rèn)就不會(huì)生效，假如我們這里顯式的聲明隨機(jī)的負(fù)載均衡的算法

下面我們將消費(fèi)者端的負(fù)載均衡策略，重新定義隨機(jī)策略下不使用默認(rèn)：

我們?cè)俅螁?dòng)所有的微服務(wù)，啟動(dòng)所有的服務(wù)參考：https://blog.csdn.net/ywl470812087/article/details/102638054

我們測(cè)試下是不是能夠隨機(jī)

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通過(guò)訪問(wèn)多次可以發(fā)現(xiàn)沒(méi)有規(guī)律也沒(méi)有輪詢,實(shí)現(xiàn)了隨機(jī)

其余的6種負(fù)載均衡策略都是可以這樣實(shí)現(xiàn)的，比如RetryRule重試策略等等

總結(jié)

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