Spring Cloud Ribbon是基于Netflix Ribbon实现的一套客户端负载均衡的工具。
简单地说，Ribbon是Netflix发布的开源项目，主要功能是提供客户端的软件负载均衡算法，将Netflix的中间层服务连接在一起。Ribbon客户端组件提供了一系列完善的配置项如连接超时，重试等。简单地说，就是在配置文件中列出Load Balancer（简称LB）后面所有的机器，Ribbon会自动的帮助你基于某种规则(如简单轮询、随机连接等)去连接这些机器。我们也很容易使用Ribbon实现自定义的负载均衡算法。
LB，即负载均衡(Load Balance)，在微服务或分布式集群中经常用的一种应用。负载均衡简单的说就是将用户的请求平摊的分配到多个服务上，从而达到系统的HA(高可用)。
常见的负载均衡软件有Nginx，LVS，硬件F5等。
.
LB分为集中式LB和进程内LB。
.
集中式LB：即在服务的消费方和提供方之间使用独立的LB设施(可以是硬件如F5，也可以是软件如Nginx)，由该设施负责把访问请求通过某种策略转发至服务的提供方。
.
进程内LB：将LB逻辑集成到消费方，消费方从服务注册中心获知有哪些地址可用，然后自己再从这些地址中选择出一个合适的服务器。Ribbon就属于进程内LB，它只是一个类库，集成于消费方进程，消费方通过它来获取到服务提供方的地址。
参考文档地址与源码：https://github.com/Netflix/ribbon/wiki
Ribbon工作步骤
①先选择EurekaServer，它优先选择在同一个区域内负载较少的Server；
② 根据用户指定的策略，从Server取到的服务注册列表中选择一个地址。
Ribbon提供了多种策略，如轮询、随机和根据响应时间加权。
【1】消费者项目配置与修改
基础项目地址：GitHub项目地址。
① pom文件
<dependencies>
<dependency><!-- 自己定义的api -->
<groupId>com.web.springcloud</groupId>
<artifactId>microservicecloud-api</artifactId>
<version>${project.version}</version>
</dependency>
<!-- Cloud-Ribbon相关 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-config</artifactId>
</dependency>
<!-- Spring Boot相关 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- 修改后立即生效，热部署相关 -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>springloaded</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
</dependencies>② application.yml
server:
port: 80
spring:
application:
name: microservicecloud-consumer
eureka:
instance:
prefer-ip-address: true # 注册服务的时候使用服务的ip地址
client:
register-with-eureka: false # 不向服务注册中心注册自己
service-url:
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/
# defaultZone: http://localhost:7001/eureka/③自定义配置类注册RestTemplate开启负载均衡
@Configuration
public class ConfigBean {
@LoadBalanced//开启负载均衡机制
@Bean
public RestTemplate restTemplate(){
return new RestTemplate(); // 用来进行HTTP通信
}
}
④ 主启动类添加@EnableEurekaClient
@SpringBootApplication
@EnableEurekaClient
public class DeptConsumer80_App
{
public static void main(String[] args)
{
SpringApplication.run(DeptConsumer80_App.class, args);
}
}⑤ 修改客户端访问类
@RestController
public class DeptController_Consumer
{
// private static final String REST_URL_PREFIX = "http://localhost:8001";
private static final String REST_URL_PREFIX = "http://MICROSERVICECLOUD-DEPT";
//这里使用服务名，也就是服务提供者应用名大写
@Autowired
private RestTemplate restTemplate;
//...
}⑥ 测试
分别依次启动服务注册中心7001，7002和7003，服务提供者8001和服务消费者80，浏览器访问：http://localhost/consumer/dept/get/1，界面如下：
【2】构建并启动多个服务提供者
① 参考microservicecloud-provider-dept-8001，分别新建8002 8003
② 新建8002 8003数据库，各自微服务分别连各自数据库
③ 修改8002、8003各自yml
参考8001的yml,主要修改的地方有端口，数据库连接url和自定义服务实例名(instance-id)，但是一定不要修改应用名–spring.application.name!!!
8002yml修改如下：
server:
port: 8002
mybatis:
config-location: classpath:mybatis/mybatis.cfg.xml # mybatis配置文件所在路径
type-aliases-package: com.web.springcloud.entities # 所有Entity别名类所在包
mapper-locations:
- classpath:mybatis/mapper/**/*.xml # mapper映射文件
spring:
application:
name: microservicecloud-dept # 这里不能修改
datasource:
type: com.alibaba.druid.pool.DruidDataSource # 当前数据源操作类型
driver-class-name: com.mysql.jdbc.Driver # mysql驱动包
# driver-class-name: org.gjt.mm.mysql.Driver # mysql驱动包
url: jdbc:mysql://localhost:3306/clouddb02 # 数据库名称
username: root
password: 123456
initialSize: 5
minIdle: 5
maxActive: 20
maxWait: 60000
timeBetweenEvictionRunsMillis: 60000
minEvictableIdleTimeMillis: 300000
validationQuery: SELECT 1 FROM DUAL
testWhileIdle: true
testOnBorrow: true
testOnReturn: false
poolPreparedStatements: true
#配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
filters: stat,wall,log4j
maxPoolPreparedStatementPerConnectionSize: 20
useGlobalDataSourceStat: true
connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500
# dbcp2:
# min-idle: 5 # 数据库连接池的最小维持连接数
# initial-size: 5 # 初始化连接数
# max-total: 5 # 最大连接数
# max-wait-millis: 200 # 等待连接获取的最大超时时间
eureka:
client: #客户端注册进eureka服务列表内
service-url:
defaultZone: http://eureka7001.com:7001/eureka/,http://eureka7002.com:7002/eureka/,http://eureka7003.com:7003/eureka/
# defaultZone: http://localhost:7001/eureka/
instance:
instance-id: microservicecloud-dept8002 # 自定义服务实例Id
prefer-ip-address: true #访问路径可以显示IP地址
# http://192.168.2.100:8002/info优化显示
info:
app.name: web-microservicecloud
company.name: www.web.com
build.artifactId: $project.artifactId$
build.version: $project.version$
④ 分别启动服务中心7001 7002 7003和服务提供者8001 8002 8003
⑤ 启动服务消费者进行多次测试(此时RestTemplate已经添加了@LoadBalanced注解)
默认负载均衡算法为轮询算法！！！
总结：Ribbon其实就是一个软负载均衡的客户端组件，它可以和其他所需请求的客户端结合使用，和Eureka结合只是其中一个实例。
【3】Ribbon核心组件IRule
IRule：根据特定算法从服务列表中选取一个要访问的服务。
/**
* 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();
}其实现类如下：
① RoundRobinRule
最基础的轮询算法–默认使用的算法。
② RandomRule
见名知意，随机选取。
③ AvailabilityFilteringRule
会先过滤掉由于多次访问故障而处于断路器跳闸状态的服务，还有并发的连接数量超过阈值的服务。然后对剩余的服务列表按照轮询策略进行访问。
④ WeightedResponseTimeRule
根据平均响应时间计算所有服务的权重，响应时间越快服务权重越大被选中的概率越高。刚启动时如果统计信息不足，会使用 RoundRobinRule策略。等统计信息足够，会切换到WeightedResponseTimeRule。
⑤ RetryRule
先按照 RoundRobinRule策略获取服务，如果获取服务失败则在指定时间内会进行重试获取可用的服务。
⑥ BestAvailableRule
会先过滤掉由于多次访问故障而处于断路器跳闸状态的服务,然后选取一个并发量最小的服务。
⑦ ZoneAvoidanceRule
复合判断Server所在区域的性能和Server的可用性来选择服务器。
【4】为什么IRule默认使用RoundRobinRule？
① 首先从RestTemplate添加注解@LoadBalanced 可知，负载均衡离不开LoadBalancerClient
/**
* Annotation to mark a RestTemplate bean to be configured to use a LoadBalancerClient
* @author Spencer Gibb
*/
@Target({ ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Qualifier
public @interface LoadBalanced {
}该接口LoadBalancerClient只有一个实现类：RibbonLoadBalancerClient
② RibbonLoadBalancerClient
/*
* Copyright 2013-2015 the original author or authors.
*
* 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.springframework.cloud.netflix.ribbon;
import java.io.IOException;
import java.net.URI;
import java.util.Collections;
import java.util.Map;
import org.springframework.cloud.client.DefaultServiceInstance;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.cloud.client.loadbalancer.LoadBalancerRequest;
import org.springframework.util.Assert;
import org.springframework.util.ReflectionUtils;
import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.ILoadBalancer;
import com.netflix.loadbalancer.Server;
/**
* @author Spencer Gibb
* @author Dave Syer
* @author Ryan Baxter
*/
public class RibbonLoadBalancerClient implements LoadBalancerClient {
private SpringClientFactory clientFactory;
public RibbonLoadBalancerClient(SpringClientFactory clientFactory) {
this.clientFactory = clientFactory;
}
@Override
public URI reconstructURI(ServiceInstance instance, URI original) {
Assert.notNull(instance, "instance can not be null");
String serviceId = instance.getServiceId();
RibbonLoadBalancerContext context = this.clientFactory
.getLoadBalancerContext(serviceId);
Server server = new Server(instance.getHost(), instance.getPort());
IClientConfig clientConfig = clientFactory.getClientConfig(serviceId);
ServerIntrospector serverIntrospector = serverIntrospector(serviceId);
URI uri = RibbonUtils.updateToHttpsIfNeeded(original, clientConfig,
serverIntrospector, server);
return context.reconstructURIWithServer(server, uri);
}
@Override
public ServiceInstance choose(String serviceId) {
Server server = getServer(serviceId);
if (server == null) {
return null;
}
return new RibbonServer(serviceId, server, isSecure(server, serviceId),
serverIntrospector(serviceId).getMetadata(server));
}
@Override
public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
Server server = getServer(loadBalancer);
if (server == null) {
throw new IllegalStateException("No instances available for " + serviceId);
}
RibbonServer ribbonServer = new RibbonServer(serviceId, server, isSecure(server,
serviceId), serverIntrospector(serviceId).getMetadata(server));
return execute(serviceId, ribbonServer, request);
}
@Override
public <T> T execute(String serviceId, ServiceInstance serviceInstance, LoadBalancerRequest<T> request) throws IOException {
Server server = null;
if(serviceInstance instanceof RibbonServer) {
server = ((RibbonServer)serviceInstance).getServer();
}
if (server == null) {
throw new IllegalStateException("No instances available for " + serviceId);
}
RibbonLoadBalancerContext context = this.clientFactory
.getLoadBalancerContext(serviceId);
RibbonStatsRecorder statsRecorder = new RibbonStatsRecorder(context, server);
try {
T returnVal = request.apply(serviceInstance);
statsRecorder.recordStats(returnVal);
return returnVal;
}
// catch IOException and rethrow so RestTemplate behaves correctly
catch (IOException ex) {
statsRecorder.recordStats(ex);
throw ex;
}
catch (Exception ex) {
statsRecorder.recordStats(ex);
ReflectionUtils.rethrowRuntimeException(ex);
}
return null;
}
private ServerIntrospector serverIntrospector(String serviceId) {
ServerIntrospector serverIntrospector = this.clientFactory.getInstance(serviceId,
ServerIntrospector.class);
if (serverIntrospector == null) {
serverIntrospector = new DefaultServerIntrospector();
}
return serverIntrospector;
}
private boolean isSecure(Server server, String serviceId) {
IClientConfig config = this.clientFactory.getClientConfig(serviceId);
ServerIntrospector serverIntrospector = serverIntrospector(serviceId);
return RibbonUtils.isSecure(config, serverIntrospector, server);
}
protected Server getServer(String serviceId) {
return getServer(getLoadBalancer(serviceId));
}
protected Server getServer(ILoadBalancer loadBalancer) {
if (loadBalancer == null) {
return null;
}
return loadBalancer.chooseServer("default"); // TODO: better handling of key
}
protected ILoadBalancer getLoadBalancer(String serviceId) {
return this.clientFactory.getLoadBalancer(serviceId);
}
public static class RibbonServer implements ServiceInstance {
private final String serviceId;
private final Server server;
private final boolean secure;
private Map<String, String> metadata;
public RibbonServer(String serviceId, Server server) {
this(serviceId, server, false, Collections.<String, String> emptyMap());
}
public RibbonServer(String serviceId, Server server, boolean secure,
Map<String, String> metadata) {
this.serviceId = serviceId;
this.server = server;
this.secure = secure;
this.metadata = metadata;
}
@Override
public String getServiceId() {
return this.serviceId;
}
@Override
public String getHost() {
return this.server.getHost();
}
@Override
public int getPort() {
return this.server.getPort();
}
@Override
public boolean isSecure() {
return this.secure;
}
@Override
public URI getUri() {
return DefaultServiceInstance.getUri(this);
}
@Override
public Map<String, String> getMetadata() {
return this.metadata;
}
public Server getServer() {
return this.server;
}
@Override
public String toString() {
final StringBuffer sb = new StringBuffer("RibbonServer{");
sb.append("serviceId='").append(serviceId).append('\'');
sb.append(", server=").append(server);
sb.append(", secure=").append(secure);
sb.append(", metadata=").append(metadata);
sb.append('}');
return sb.toString();
}
}
}
首先需要拿到ILoadBalancer 才能获取Server：
protected ILoadBalancer getLoadBalancer(String serviceId) {
return this.clientFactory.getLoadBalancer(serviceId);
}其中在获取Server时，默认key–default :
protected Server getServer(ILoadBalancer loadBalancer) {
if (loadBalancer == null) {
return null;
}
return loadBalancer.chooseServer("default"); // TODO: better handling of key
}③ ILoadBalancer
源码如下：
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
*/
@Deprecated
public 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();
}
实现类如下：
④ BaseLoadBalancer
/**
* A basic implementation of the load balancer where an arbitrary list of
* servers can be set as the server pool. A ping can be set to determine the
* liveness of a server. Internally, this class maintains an "all" server list
* and an "up" server list and use them depending on what the caller asks for.
*
* @author stonse
*
*/
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();
// 这里这里这里！！！
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>());
protected ReadWriteLock allServerLock = new ReentrantReadWriteLock();
protected ReadWriteLock upServerLock = new ReentrantReadWriteLock();
protected String name = DEFAULT_NAME;
protected Timer lbTimer = null;
protected int pingIntervalSeconds = 10;
protected int maxTotalPingTimeSeconds = 5;
protected Comparator<Server> serverComparator = new ServerComparator();
protected AtomicBoolean pingInProgress = new AtomicBoolean(false);
protected LoadBalancerStats lbStats;
private volatile Counter counter = Monitors.newCounter("LoadBalancer_ChooseServer");
private PrimeConnections primeConnections;
private volatile boolean enablePrimingConnections = false;
private IClientConfig config;
private List<ServerListChangeListener> changeListeners = new CopyOnWriteArrayList<ServerListChangeListener>();
private List<ServerStatusChangeListener> serverStatusListeners = new CopyOnWriteArrayList<ServerStatusChangeListener>();
/**
* Default constructor which sets name as "default", sets null ping, and
* {@link RoundRobinRule} as the rule.
* <p>
* This constructor is mainly used by {@link ClientFactory}. Calling this
* constructor must be followed by calling {@link #init()} or
* {@link #initWithNiwsConfig(IClientConfig)} to complete initialization.
* This constructor is provided for reflection. When constructing
* programatically, it is recommended to use other constructors.
*/
public BaseLoadBalancer() {
this.name = DEFAULT_NAME;
this.ping = null;
setRule(DEFAULT_RULE);
// 空参使用默认Rule
setupPingTask();
lbStats = new LoadBalancerStats(DEFAULT_NAME);
}
public BaseLoadBalancer(String lbName, IRule rule, LoadBalancerStats lbStats) {
this(lbName, rule, lbStats, null);
}
//...
}其中setRule(IRule rule) :
/* Ignore null rules */
public void setRule(IRule rule) {
if (rule != null) {
this.rule = rule;
} else {
/* default rule */
this.rule = new RoundRobinRule();
}
if (this.rule.getLoadBalancer() != this) {
this.rule.setLoadBalancer(this);
}
}到此明白了，为什么会默认使用RoundRobinRule ！！！
【5】为什么RestTemplate添加注解@LoadBalanced就可以实现负载均衡？
实例如下：
@Configuration
public class ConfigBean {
@LoadBalanced//开启负载均衡机制
@Bean
public RestTemplate restTemplate(){
return new RestTemplate(); // 用来进行HTTP通信
}
}
这里就要联想到SpringBoot中的许许多多自动配置类！！！
LoadBalancerAutoConfiguration 源码如下：
/**
* Auto configuration for Ribbon (client side load balancing).
*
* @author Spencer Gibb
* @author Dave Syer
* @author Will Tran
*/
@Configuration
@ConditionalOnClass(RestTemplate.class)
@ConditionalOnBean(LoadBalancerClient.class)
@EnableConfigurationProperties(LoadBalancerRetryProperties.class)
public class LoadBalancerAutoConfiguration {
@LoadBalanced
@Autowired(required = false)
private List<RestTemplate> restTemplates = Collections.emptyList();
@Bean
public SmartInitializingSingleton loadBalancedRestTemplateInitializer(
final List<RestTemplateCustomizer> customizers) {
return new SmartInitializingSingleton() {
@Override
public void afterSingletonsInstantiated() {
for (RestTemplate restTemplate : LoadBalancerAutoConfiguration.this.restTemplates) {
for (RestTemplateCustomizer customizer : customizers) {
customizer.customize(restTemplate);
}
}
}
};
}
@Autowired(required = false)
private List<LoadBalancerRequestTransformer> transformers = Collections.emptyList();
@Bean
@ConditionalOnMissingBean
public LoadBalancerRequestFactory loadBalancerRequestFactory(
LoadBalancerClient loadBalancerClient) {
return new LoadBalancerRequestFactory(loadBalancerClient, transformers);
}
@Configuration
@ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate")
static class LoadBalancerInterceptorConfig {
@Bean
public LoadBalancerInterceptor ribbonInterceptor(
LoadBalancerClient loadBalancerClient,
LoadBalancerRequestFactory requestFactory) {
return new LoadBalancerInterceptor(loadBalancerClient, requestFactory);
}
@Bean
@ConditionalOnMissingBean
public RestTemplateCustomizer restTemplateCustomizer(
final LoadBalancerInterceptor loadBalancerInterceptor) {
return new RestTemplateCustomizer() {
@Override
public void customize(RestTemplate restTemplate) {
List<ClientHttpRequestInterceptor> list = new ArrayList<>(
restTemplate.getInterceptors());
list.add(loadBalancerInterceptor);
restTemplate.setInterceptors(list);
}
};
}
}
@Configuration
@ConditionalOnClass(RetryTemplate.class)
static class RetryAutoConfiguration {
@Bean
public RetryTemplate retryTemplate() {
RetryTemplate template = new RetryTemplate();
template.setThrowLastExceptionOnExhausted(true);
return template;
}
@Bean
@ConditionalOnMissingBean
public LoadBalancedRetryPolicyFactory loadBalancedRetryPolicyFactory() {
return new LoadBalancedRetryPolicyFactory.NeverRetryFactory();
}
@Bean
public RetryLoadBalancerInterceptor ribbonInterceptor(
LoadBalancerClient loadBalancerClient, LoadBalancerRetryProperties properties,
LoadBalancedRetryPolicyFactory lbRetryPolicyFactory,
LoadBalancerRequestFactory requestFactory) {
return new RetryLoadBalancerInterceptor(loadBalancerClient, retryTemplate(), properties,
lbRetryPolicyFactory, requestFactory);
}
@Bean
@ConditionalOnMissingBean
public RestTemplateCustomizer restTemplateCustomizer(
final RetryLoadBalancerInterceptor loadBalancerInterceptor) {
return new RestTemplateCustomizer() {
@Override
public void customize(RestTemplate restTemplate) {
List<ClientHttpRequestInterceptor> list = new ArrayList<>(
restTemplate.getInterceptors());
list.add(loadBalancerInterceptor);
restTemplate.setInterceptors(list);
}
};
}
}
}
【6】其他算法替换默认RoundRobinRule
如，使用RandomRule替换RoundRobinRule：
@Configuration
public class ConfigBean {
@LoadBalanced//开启负载均衡机制
@Bean
public RestTemplate restTemplate(){
return new RestTemplate(); // 用来进行HTTP通信
}
// 在容器中注册IRule即可
@Bean
public IRule myRule(){
return new RandomRule();
}
}【7】自定义Ribbon负载均衡策略
① 主启动类添加@RibbonClient注解
在启动微服务的时候就能去加载我们的自定义Ribbon配置类，从而使配置生效。
@SpringBootApplication
//在启动该微服务的时候就能去加载我们的自定义Ribbon配置类，从而使配置生效
@RibbonClient(name="MICROSERVICECLOUD-DEPT",configuration=MySelfRule.class)
@EnableDiscoveryClient //服务发现
public class DeptConsumer80_App
{
public static void main(String[] args)
{
SpringApplication.run(DeptConsumer80_App.class, args);
}
}解释：在调用MICROSERVICECLOUD-DEPT服务时，使用我们自定义的MySelfRule负载均衡策略。
② 自定义配置类位置
这个自定义配置类不能放在@ComponentScan所扫描的当前包与子包下，否则我们自定义的这个配置类就会被所有的Ribbon客户端共享，也就是说我们达不到特殊化定制的目的。
③ 两个需求
第一，针对服务MICROSERVICECLOUD-DEPT使用Ribbon其他自带算法；
第二，依旧轮询策略，但是每个服务器被调用5次。
MySelfRule源码如下：
@Configuration
public class MySelfRule
{
@Bean
public IRule myRule()
{
//return new RandomRule();// Ribbon默认是轮询，我自定义为随机
//return new RoundRobinRule();// Ribbon默认是轮询，我自定义为随机
return new MyRoundRobinRule();// 我自定义为每台机器5次
}
}MyRoundRobinRule如下：
package com.web.myrule;
import java.util.List;
import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.ILoadBalancer;
import com.netflix.loadbalancer.Server;
public class MyRoundRobinRule extends AbstractLoadBalancerRule
{
// total = 0 // 当total==5以后，我们指针才能往下走，
// index = 0 // 当前对外提供服务的服务器地址，
// total需要重新置为零，但是已经达到过一个5次，我们的index = 1
// 分析：我们5次，但是微服务只有8001 8002 8003 三台，OK？
//
private int total = 0; // 总共被调用的次数，目前要求每台被调用5次
private int currentIndex = 0; // 当前提供服务的机器号
public Server choose(ILoadBalancer lb, Object key)
{
if (lb == null) {
return null;
}
Server server = null;
while (server == null) {
if (Thread.interrupted()) {
return null;
}
List<Server> upList = lb.getReachableServers();
List<Server> allList = lb.getAllServers();
int serverCount = allList.size();
if (serverCount == 0) {
/*
* No servers. End regardless of pass, because subsequent passes only get more
* restrictive.
*/
return null;
}
// int index = rand.nextInt(serverCount);// java.util.Random().nextInt(3);
// server = upList.get(index);
// private int total = 0; // 总共被调用的次数，目前要求每台被调用5次
// private int currentIndex = 0; // 当前提供服务的机器号
if(total < 5)
{
server = upList.get(currentIndex);
total++;
}else {
total = 0;
currentIndex++;
if(currentIndex >= upList.size())
{
currentIndex = 0;
}
}
if (server == null) {
/*
* The only time this should happen is if the server list were somehow trimmed.
* This is a transient condition. Retry after yielding.
*/
Thread.yield();
continue;
}
if (server.isAlive()) {
return (server);
}
// Shouldn't actually happen.. but must be transient or a bug.
server = null;
Thread.yield();
}
return server;
}
@Override
public Server choose(Object key)
{
return choose(getLoadBalancer(), key);
}
@Override
public void initWithNiwsConfig(IClientConfig clientConfig)
{
// TODO Auto-generated method stub
}
}代码结构图如下：
