Spring Cloud微服务开发笔记5——Ribbon负载均衡策略规则定制

阳光穿透心脏的1/2处 2022-03-15 15:15 594阅读 0赞

# [Spring Cloud微服务开发笔记5——Ribbon负载均衡策略规则定制][Spring Cloud_5_Ribbon] #

上一篇文章单独介绍了Ribbon框架的使用，及其如何实现客户端对服务访问的负载均衡，但只是单独从Ribbon框架实现，没有涉及spring cloud。本文着力介绍Ribbon的负载均衡机制，下一篇文章再在spring中继承Ribbon。

# Ribbon负载均衡器 #

上一篇文章我们已经实现了一个客户端负载均衡请求web服务的示例。

![164456_xZA6_1156339.png][]

当时，我们留了一个伏笔，其中的负载均衡的规则策略可以定制，那么本文着重研究策略定制这部分内容，其他的ribbon客户端的构建和请求方法请参见上一篇文章。

ribbon的负载均衡的策略规则是独立的，即这部分功能可以独立于时间的客户端构造和请求发送。我们需要做的是，实现一个IRule接口的对象，对象里面当然会有一些需要你去覆盖实现的方法，这些方法中需要用代码实现你定制的服务器选择策略，但不包括实际的网络请求操作。

除了可以自己定制，Ribbon已经为我们设计了几个现成的规则策略，分别对应于多个不同IRule实现类。我们只需要将这些类对象传给负载均衡器ILoadBalancer的chooseServer()就可以了。其中，默认情况下，BaseLoadBalancer会选择轮询各个server的策略方式，叫做RoundRobinRule。源码如下：

public class BaseLoadBalancer extends AbstractLoadBalancer implements
            PrimeConnections.PrimeConnectionListener, IClientConfigAware {
    
        private static Logger logger = LoggerFactory
                .getLogger(BaseLoadBalancer.class);
        private final static IRule DEFAULT_RULE = new RoundRobinRule();
        private final static SerialPingStrategy DEFAULT_PING_STRATEGY = new SerialPingStrategy();
        private static final String DEFAULT_NAME = "default";
        private static final String PREFIX = "LoadBalancer_";
    
        protected IRule rule = DEFAULT_RULE;
    
        protected IPingStrategy pingStrategy = DEFAULT_PING_STRATEGY;
    
        protected IPing ping = null;
    
        @Monitor(name = PREFIX + "AllServerList", type = DataSourceType.INFORMATIONAL)
        protected volatile List<Server> allServerList = Collections
                .synchronizedList(new ArrayList<Server>());
        @Monitor(name = PREFIX + "UpServerList", type = DataSourceType.INFORMATIONAL)
        protected volatile List<Server> upServerList = Collections
                .synchronizedList(new ArrayList<Server>());

好，先说到这里，我们来实验一下默认的规则策略：

第一步，我们先构建一个负载均衡器，类型BaseLoadBalancer，它是ILoadBalancer的实现类。

![173126_oUn0_1156339.png][]

负载均衡器，需要配置两样东西：

1、服务地址列表——谁来参选？

2、选择策略规则——怎么选？

第二步，按照服务方的地址端口列表，配置一个Server的List。添加给负载均衡器。

第三步，构造或选择一个IRule实现类，通过ConfigurationMannager来配置【客户端名称】.ribbon.NFLoadBalancerRuleClassName属性，将配置键赋予一个规则类。这里我们不操作，使用默认的。

package com.happybks.invokers;
    
    import java.util.ArrayList;
    import java.util.List;
    
    import com.netflix.loadbalancer.BaseLoadBalancer;
    import com.netflix.loadbalancer.ILoadBalancer;
    import com.netflix.loadbalancer.Server;
    
    public class BalancerApplication {
    
    	public static void main(String[] args) {
    		ILoadBalancer balancer=new BaseLoadBalancer();
    		
    		List<Server> servers = new ArrayList<Server>();
    		servers.add(new Server("127.0.0.1",8091));
    		servers.add(new Server("127.0.0.1",8092));
    		balancer.addServers(servers);
    		
    		for(int i=0;i<10;i++) {
    			Server choosedServer = balancer.chooseServer(null);
    			System.out.println(choosedServer);
    		}
    
    	}
    
    }

默认策略，就用BaseLoadBalancer类默认初始化定义好的，chooseServer方法会为我们选择已有的RoundRobinRule。

（本文出自ochina博主happBKs的博文：https://my.oschina.net/happyBKs/blog/1787825）

源码如下：

private final static IRule DEFAULT_RULE = new RoundRobinRule();

/*
         * Get the alive server dedicated to key
         * 
         * @return the dedicated server
         */
        public Server chooseServer(Object key) {
            if (counter == null) {
                counter = createCounter();
            }
            counter.increment();
            if (rule == null) {
                return null;
            } else {
                try {
                    return rule.choose(key);
                } catch (Exception e) {
                    logger.warn("LoadBalancer [{}]:  Error choosing server for key {}", name, key, e);
                    return null;
                }
            }
        }

我们运行代码：10次选择server的结果打印如下：

16:41:10.754 [main] WARN com.netflix.config.sources.URLConfigurationSource - No URLs will be polled as dynamic configuration sources.
    16:41:10.758 [main] INFO com.netflix.config.sources.URLConfigurationSource - To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
    16:41:10.766 [main] INFO com.netflix.config.DynamicPropertyFactory - DynamicPropertyFactory is initialized with configuration sources: com.netflix.config.ConcurrentCompositeConfiguration@75bd9247
    16:41:10.818 [main] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [default]: clearing server list (SET op)
    16:41:10.819 [main] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [default]:  addServer [127.0.0.1:8091]
    16:41:10.819 [main] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [default]:  addServer [127.0.0.1:8092]
    127.0.0.1:8092
    127.0.0.1:8091
    127.0.0.1:8092
    127.0.0.1:8091
    127.0.0.1:8092
    127.0.0.1:8091
    127.0.0.1:8092
    127.0.0.1:8091
    127.0.0.1:8092
    127.0.0.1:8091

# 关于负载均衡相关的四个配置项 #

这些配置项的前缀是【客户端名称】.ribbon

The supported properties are listed below and should be prefixed by `<clientName>.ribbon.`:

*  `NFLoadBalancerClassName`: should implement `ILoadBalancer`
 *  `NFLoadBalancerRuleClassName`: should implement `IRule`
 *  `NFLoadBalancerPingClassName`: should implement `IPing`
 *  `NIWSServerListClassName`: should implement `ServerList`
 *  `NIWSServerListFilterClassName` should implement `ServerListFilter`

其中比较重要的是`NFLoadBalancerRuleClassName`，我们可以通过这个配置项定制需要的负载均衡规则，可以是ribbon提供的原生的几种规则类，也可以是自己实现的规则类，这些类都实现了IRule接口。

`NFLoadBalancerPingClassName`用于配置查看服务器是否存活。

`NFLoadBalancerRuleClassName`指定负载均衡器的实现类。当然，可以设置自己实现的负载均衡器。

`NIWSServerListClassName`是服务器列表的处理类，用来维护服务器列表的。Ribbon已经实现了动态服务器列表。

`NIWSServerListFilterClassName`是服务器的拦截类。

## 负载均衡的两种配置方法： ##

一种直接调用ConfigurationManager获取配置实例，然后设置配置属性；一种是在application.yml中配置。

## 自定义策略规则： ##

下面我们以一个示例来构建一个自己的负载均衡规则。

示例：构建一个60%的概率选择8091,40%概率选择8092的规则

我们构建一个实现IRule接口的实现类：

package com.happybks.invokers;
    
    import java.util.List;
    import java.util.Random;
    
    import com.netflix.loadbalancer.BaseLoadBalancer;
    import com.netflix.loadbalancer.ILoadBalancer;
    import com.netflix.loadbalancer.IRule;
    import com.netflix.loadbalancer.Server;
    
    public class MyProbabilityRandomRule implements IRule {
    
    	ILoadBalancer balancer = new BaseLoadBalancer();
    
    	@Override
    	public Server choose(Object key) {
    		List<Server> allServers = balancer.getAllServers();
    		Random random = new Random();
    		final int number = random.nextInt(10);
    		if (number < 7) {
    			return findServer(allServers,8091);
    		}
    		return findServer(allServers,8092);
    	}
    
    	private Server findServer(List<Server> allServers, int port) {
    		for (Server server : allServers) {
    			if (server.getPort() == port) {
    				return server;
    			}
    		}
    		System.out.println("NULL port="+port);
    		return null;
    	}
    
    	@Override
    	public void setLoadBalancer(ILoadBalancer lb) {
    		this.balancer = lb;
    	}
    
    	@Override
    	public ILoadBalancer getLoadBalancer() {
    		return this.balancer;
    	}
    
    }

客户端的请求程序这里我们还是直接在一个普通的main方法中实现

我们首先需要配置请求服务器列表，这个上篇文章已经介绍过。

之后我们对对应的客户端配置它的ribbon.NFLoadBalancerRuleClassName配置为我们刚才定义的那个实现了IRule的实现类的类名全名，注意：是IRule实现类的全名，一个字符串，不是class。

package com.happybks.invokers;
    
    import com.netflix.client.ClientException;
    import com.netflix.client.ClientFactory;
    import com.netflix.client.http.HttpRequest;
    import com.netflix.client.http.HttpResponse;
    import com.netflix.config.ConfigurationManager;
    import com.netflix.niws.client.http.RestClient;
    
    public class MyRuleClientApplication {
    
    	public static void main(String[] args) throws Exception {
    		// 1、设置请求的服务器
    		ConfigurationManager.getConfigInstance().setProperty("happybks-client.ribbon.listOfServers",
    				"localhost:8091,localhost:8092"); // 1
    		// 2、 配置规则处理类
    		//本示例略，先默认使用其默认负载均衡策略规则
    		ConfigurationManager.getConfigInstance().setProperty("happybks-client.ribbon.NFLoadBalancerRuleClassName",MyProbabilityRandomRule.class.getName());
    
    		// 3、获取 REST 请求客户端
    		RestClient client = (RestClient) ClientFactory.getNamedClient("happybks-client");
    
    		// 4、创建请求实例
    		HttpRequest request = HttpRequest.newBuilder().uri("/carsInfo/onsale").build();
    
    		// 5、发 送 10 次请求到服务器中
    		for (int i = 0; i < 10; i++) {
    			System.out.println("the "+(i+1)+"th: ");
    			HttpResponse response = client.executeWithLoadBalancer(request);
    			String result = response.getEntity(String.class);
    			System.out.println(result);
    		}
    	}
    
    }

响应请求的服务方程序请参见之前的文章，我们不再累述。然后我们看看运行结果：

22:52:27.695 [main] WARN com.netflix.config.sources.URLConfigurationSource - No URLs will be polled as dynamic configuration sources.
    22:52:27.701 [main] INFO com.netflix.config.sources.URLConfigurationSource - To enable URLs as dynamic configuration sources, define System property archaius.configurationSource.additionalUrls or make config.properties available on classpath.
    22:52:27.834 [main] INFO com.netflix.config.DynamicPropertyFactory - DynamicPropertyFactory is initialized with configuration sources: com.netflix.config.ConcurrentCompositeConfiguration@97e1986
    22:52:28.787 [main] INFO com.netflix.http4.ConnectionPoolCleaner - Initializing ConnectionPoolCleaner for NFHttpClient:happybks-client
    22:52:28.798 [Connection pool clean up thread] DEBUG com.netflix.http4.ConnectionPoolCleaner - Connection pool clean up started for client happybks-client
    22:52:28.799 [Connection pool clean up thread] DEBUG com.netflix.http4.MonitoredConnectionManager - Closing expired connections
    22:52:28.799 [Connection pool clean up thread] DEBUG com.netflix.http4.NamedConnectionPool - Closing expired connections
    22:52:28.799 [Connection pool clean up thread] DEBUG com.netflix.http4.MonitoredConnectionManager - Closing connections idle longer than 30000 MILLISECONDS
    22:52:28.800 [Connection pool clean up thread] DEBUG com.netflix.http4.NamedConnectionPool - Closing connections idle longer than 30000 MILLISECONDS
    22:52:29.032 [main] WARN com.netflix.client.ClientFactory - Class com.happybks.invokers.MyProbabilityRandomRule neither implements IClientConfigAware nor provides a constructor with IClientConfig as the parameter. Only default constructor will be used.
    
    22:52:29.035 [main] INFO com.netflix.loadbalancer.BaseLoadBalancer - Client: happybks-client instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=happybks-client,current list of Servers=[],Load balancer stats=Zone stats: {},Server stats: []}ServerList:null
    22:52:29.111 [main] INFO com.netflix.loadbalancer.DynamicServerListLoadBalancer - Using serverListUpdater PollingServerListUpdater
    22:52:29.145 [main] WARN com.netflix.client.ClientFactory - Class com.happybks.invokers.MyProbabilityRandomRule neither implements IClientConfigAware nor provides a constructor with IClientConfig as the parameter. Only default constructor will be used.
    22:52:29.165 [main] INFO com.netflix.loadbalancer.DynamicServerListLoadBalancer - DynamicServerListLoadBalancer for client happybks-client initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=happybks-client,current list of Servers=[localhost:8091, localhost:8092],Load balancer stats=Zone stats: {unknown=[Zone:unknown;	Instance count:2;	Active connections count: 0;	Circuit breaker tripped count: 0;	Active connections per server: 0.0;]
    },Server stats: [[Server:localhost:8092;	Zone:UNKNOWN;	Total Requests:0;	Successive connection failure:0;	Total blackout seconds:0;	Last connection made:Thu Jan 01 08:00:00 GMT+08:00 1970;	First connection made: Thu Jan 01 08:00:00 GMT+08:00 1970;	Active Connections:0;	total failure count in last (1000) msecs:0;	average resp time:0.0;	90 percentile resp time:0.0;	95 percentile resp time:0.0;	min resp time:0.0;	max resp time:0.0;	stddev resp time:0.0]
    , [Server:localhost:8091;	Zone:UNKNOWN;	Total Requests:0;	Successive connection failure:0;	Total blackout seconds:0;	Last connection made:Thu Jan 01 08:00:00 GMT+08:00 1970;	First connection made: Thu Jan 01 08:00:00 GMT+08:00 1970;	Active Connections:0;	total failure count in last (1000) msecs:0;	average resp time:0.0;	90 percentile resp time:0.0;	95 percentile resp time:0.0;	min resp time:0.0;	max resp time:0.0;	stddev resp time:0.0]
    ]}ServerList:com.netflix.loadbalancer.ConfigurationBasedServerList@152aa092
    22:52:29.165 [main] INFO com.netflix.client.ClientFactory - Client: happybks-client instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=happybks-client,current list of Servers=[localhost:8091, localhost:8092],Load balancer stats=Zone stats: {unknown=[Zone:unknown;	Instance count:2;	Active connections count: 0;	Circuit breaker tripped count: 0;	Active connections per server: 0.0;]
    },Server stats: [[Server:localhost:8092;	Zone:UNKNOWN;	Total Requests:0;	Successive connection failure:0;	Total blackout seconds:0;	Last connection made:Thu Jan 01 08:00:00 GMT+08:00 1970;	First connection made: Thu Jan 01 08:00:00 GMT+08:00 1970;	Active Connections:0;	total failure count in last (1000) msecs:0;	average resp time:0.0;	90 percentile resp time:0.0;	95 percentile resp time:0.0;	min resp time:0.0;	max resp time:0.0;	stddev resp time:0.0]
    , [Server:localhost:8091;	Zone:UNKNOWN;	Total Requests:0;	Successive connection failure:0;	Total blackout seconds:0;	Last connection made:Thu Jan 01 08:00:00 GMT+08:00 1970;	First connection made: Thu Jan 01 08:00:00 GMT+08:00 1970;	Active Connections:0;	total failure count in last (1000) msecs:0;	average resp time:0.0;	90 percentile resp time:0.0;	95 percentile resp time:0.0;	min resp time:0.0;	max resp time:0.0;	stddev resp time:0.0]
    ]}ServerList:com.netflix.loadbalancer.ConfigurationBasedServerList@152aa092
    22:52:29.167 [main] INFO com.netflix.client.ClientFactory - Client Registered:com.netflix.niws.client.http.RestClient@44a7bfbc
    the 1th: 
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.DynamicServerListLoadBalancer - List of Servers for happybks-client obtained from Discovery client: [localhost:8091, localhost:8092]
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.DynamicServerListLoadBalancer - Filtered List of Servers for happybks-client obtained from Discovery client: [localhost:8091, localhost:8092]
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [happybks-client]: clearing server list (SET op)
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [happybks-client]:  addServer [localhost:8091]
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [happybks-client]:  addServer [localhost:8092]
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.DynamicServerListLoadBalancer - Setting server list for zones: {unknown=[localhost:8091, localhost:8092]}
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [happybks-client_unknown]: clearing server list (SET op)
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [happybks-client_unknown]:  addServer [localhost:8091]
    22:52:30.115 [PollingServerListUpdater-0] DEBUG com.netflix.loadbalancer.BaseLoadBalancer - LoadBalancer [happybks-client_unknown]:  addServer [localhost:8092]
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8092/carsInfo/onsale"}
    the 2th: 
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8091/carsInfo/onsale"}
    the 3th: 
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8091/carsInfo/onsale"}
    the 4th: 
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8091/carsInfo/onsale"}
    the 5th: 
    andName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8091/carsInfo/onsale"}
    the 6th: 
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8092/carsInfo/onsale"}
    the 7th: 
    andName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8092/carsInfo/onsale"}
    the 8th: 
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8091/carsInfo/onsale"}
    the 9th: 
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8092/carsInfo/onsale"}
    the 10th: 
    {"brandName":"Volvo","price":536000.0,"serviceUrl":"http://localhost:8091/carsInfo/onsale"}
    22:52:30.889 [Thread-2] INFO com.netflix.loadbalancer.PollingServerListUpdater - Shutting down the Executor Pool for PollingServerListUpdater

从上面的结果可以看出，有6个请求为8091，剩下4个为8092，我们自己定义的规则的功能就实现了。

Ribbon内置负载均衡规则

Ribbon框架按照不同需求，已经为我们实现了许多实现了IRule接口的实现类，适用于常用的负载均衡规则。以下规则能够实现大部分负载均衡需求的应用场景，如果有更复杂的需求，可以自己实现IRule。

<table> 
 <tbody> 
  <tr> 
   <td><strong>内置负载均衡规则类</strong></td> 
   <td><strong>规则描述</strong></td> 
  </tr> 
  <tr> 
   <td>RoundRobinRule</td> 
   <td>简单轮询服务列表来选择服务器。它是Ribbon默认的负载均衡规则。</td> 
  </tr> 
  <tr> 
   <td>AvailabilityFilteringRule</td> 
   <td> <p>对以下两种服务器进行忽略：</p> <p>（1）在默认情况下，这台服务器如果3次连接失败，这台服务器就会被设置为“短路”状态。短路状态将持续30秒，如果再次连接失败，短路的持续时间就会几何级地增加。</p> <p>注意：可以通过修改配置loadbalancer.&lt;clientName&gt;.connectionFailureCountThreshold来修改连接失败多少次之后被设置为短路状态。默认是3次。</p> <p>（2）并发数过高的服务器。如果一个服务器的并发连接数过高，配置了AvailabilityFilteringRule规则的客户端也会将其忽略。并发连接数的上线，可以由客户端的&lt;clientName&gt;.&lt;clientConfigNameSpace&gt;.ActiveConnectionsLimit属性进行配置。</p> <p>&nbsp;</p> <p>&nbsp;</p> </td> 
  </tr> 
  <tr> 
   <td>WeightedResponseTimeRule</td> 
   <td> <p>为每一个服务器赋予一个权重值。服务器响应时间越长，这个服务器的权重就越小。这个规则会随机选择服务器，这个权重值会影响服务器的选择。</p> </td> 
  </tr> 
  <tr> 
   <td>ZoneAvoidanceRule</td> 
   <td>以区域可用的服务器为基础进行服务器的选择。使用Zone对服务器进行分类，这个Zone可以理解为一个机房、一个机架等。</td> 
  </tr> 
  <tr> 
   <td>BestAvailableRule</td> 
   <td>忽略哪些短路的服务器，并选择并发数较低的服务器。</td> 
  </tr> 
  <tr> 
   <td>RandomRule</td> 
   <td>随机选择一个可用的服务器。</td> 
  </tr> 
  <tr> 
   <td>Retry</td> 
   <td>重试机制的选择逻辑</td> 
  </tr> 
 </tbody> 
</table>

附录：AvailabilityFilteringRule的三个默认配置

# successive connection failures threshold to put the server in circuit tripped state, default 3
    niws.loadbalancer.<clientName>.connectionFailureCountThreshold
    
    # Maximal period that an instance can remain in "unusable" state regardless of the exponential increase, default 30
    niws.loadbalancer.<clientName>.circuitTripMaxTimeoutSeconds
    
    # threshold of concurrent connections count to skip the server, default is Integer.MAX_INT
    <clientName>.<clientConfigNameSpace>.ActiveConnectionsLimit

[Spring Cloud_5_Ribbon]: https://www.cnblogs.com/cxxjohnson/p/9027919.html
[164456_xZA6_1156339.png]: https://static.oschina.net/uploads/space/2018/0324/164456_xZA6_1156339.png
[173126_oUn0_1156339.png]: https://static.oschina.net/uploads/space/2018/0324/173126_oUn0_1156339.png