SpringCloud.H-负载均衡[服务调用]
# SpringCloud.H-负载均衡[服务调用]
笔记日期:2020.5.20
Rbbon: 文档 (opens new window)
# 1. 概述
Ribbon 简介:
Spring Cloud Ribbon 是基于Netflix Ribbon 实现的一套客户端 负载均衡的工具。
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和服务调用。Ribbon 客户端组件提供一系列完善的配置项如连接超时,重试等。简单的说,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。我们很容易使用Ribbon实现自定义的负载均衡算法。
官网资料:https://github.com/Netflix/ribbon/wiki/Getting-starte27
PS: Ribbon目前也进入维护模式,SpringCloud 想用Spring Cloud LoadBalancer 替代 Netflix 的Ribbon ,但现在 Ribbon 在生产环境中大规模部署,一时半会替不掉
# 2. 作用: LB负载均衡(Load Balance)
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)。常见的负载均衡有软件 Nginx,LVS,硬件F5 等。
- 集中式B
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,集成与消费方进程,消费方通过它来获取到服务提供方的地址。
- Ribbon 本地负载均衡客户端 和 Nginx 服务端负载均衡 区别:
- Nginx 是服务器负载均衡,客户端所有请求都会交给 nginx ,然后由 nginx 实现转发请求。即负载均衡是由服务端实现的。
- Ribbon 本地负载均衡,在调用微服务接口时候,会在注册中心上获取注册信息服务列表之后缓存到JVM本地,从而在本地实现 RPC 远程服务调用技术。
总之一句话: Ribbon 就是 负载均衡 + RestTemplate调用,最终实现RPC的远程调用
# 3. 架构
Ribbon:
Ribbon 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 结合只是其中的一个实例。
2
Ribbon 在工作时分成两步:
- 第一步先选择 EurekaServer,它优先选择在同一个区域内负载较少的server
- 第二步再根据用户指定的策略,在从server 取到的服务注册列表中选择一个地址
其中Ribbon 提供了多种策略:比如轮询、随机和根据响应时间加权
新版eureka引入了ribbon,所以不用自己引入也可以使用负载均衡
RestTemplate使用:
官网:https://docs.spring.io/spring-framework/docs/5.2.2.RELEASE/javadoc-api/org/springframework/web/client/RestTemplate.html
getForObject 方法 / getForEntity方法
示例 ** getForObject 方法 / getForEntity方法 推荐getForObject** 方法
@PostMapping(value = "/create")
public CommonResult create(@RequestBody Payment payment) {
return restTemplate.postForObject(PAYMENT_URL + "/payment/create", payment, CommonResult.class);
}
@PostMapping(value = "/create2")
public CommonResult create2(@RequestBody Payment payment) {
ResponseEntity<CommonResult> entity = restTemplate.postForEntity(PAYMENT_URL + "/payment/create", payment, CommonResult.class);
if (entity.getStatusCode().is2xxSuccessful()){
return entity.getBody();
}else {
return new CommonResult<>(4444,"操作失败");
}
}
@GetMapping(value = "/get/{id}")
public CommonResult getPayment(@PathVariable("id") Long id) {
return restTemplate.getForObject(PAYMENT_URL + "/payment/get/" + id, CommonResult.class);
}
@GetMapping(value = "/getForEntity/{id}")
public CommonResult getPayment2(@PathVariable("id") Long id) {
ResponseEntity<CommonResult> entity = restTemplate.getForEntity(PAYMENT_URL + "/payment/get/" + id, CommonResult.class);
if (entity.getStatusCode().is2xxSuccessful()) {
return entity.getBody();
}else {
return new CommonResult<>(4444,"操作失败");
}
}
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# 4. 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
- com.netflix.loadbalancer.RoundRobinRule 轮询
- com.netflix.loadbalancer.RandomRule 随机
- com.netflix.loadbalancer.RetryRule 先按照RoundRobinRule的策略获取服务,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
- WeightedResponseTimeRule 对RoundRobinRule的扩展,响应速度越快的实例选择权重越大,越容易被选择
- 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,然后选择一个并发量最小的服务
- AvailabilityFilteringRule 先过滤掉故障实例,再选择并发较小的实例 ZoneAvoidanceRule 默认规则,复合判断server所在区域的性能和server的可用性选择服务器
# 5. Ribbon 负载规则替换
# 1 . 添加规则类:
注意: 官方文档明确给出了警告:
解决警告
# 2. 自定义负载均衡规则类
@Configuration
public class MySelfRule {
@Bean
public IRule myRule(){
// 随机
return new RandomRule();
}
}
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# 6. ribbon负载均衡算法
# 1. 原理
轮询算法
rest 接口第几次请求数 % 服务器集群总数量 = 实际调用服务器位置下标
每次服务器重启后rest接口数从1开始
List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PROVIDER-SERVICE")
如:
- List[0] instances = 127.0.0.1:8002
- List[1] instances = 127.0.0.1:8001
8001 + 8002 组合成为集群,它们共计2台机器,集群总数为2,按照轮询算法原理:
总请求数 | 对应下标 | 获得服务器地址 |
---|---|---|
1 | 1 % 2 = 1 | 127.0.0.1:8001 |
2 | 2 %2 = 0 | 127.0.0.1:8002 |
3 | 3 % 2 = 1 | 127.0.0.1:8001 |
4 | 4 % 2 = 0 | 127.0.0.1:8002 |
... | ... |
# 2. 源码
点击查看
- IRule
/*
*
* 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();
}
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2.RoundRobinRule
/*
*
* 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.
* 自旋锁
*/
private int incrementAndGetModulo(int modulo) {
for (;;) {
int current = nextServerCyclicCounter.get();
int next = (current + 1) % modulo;
if (nextServerCyclicCounter.compareAndSet(current, next))
return next;
}
}
@Override
public Server choose(Object key) {
return choose(getLoadBalancer(), key);
}
@Override
public void initWithNiwsConfig(IClientConfig clientConfig) {
}
}
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# 3. . 手写一个负载均衡算法
原理+JUC(CAS+自旋锁复习)
# 1.改写提供者(2个)
@GetMapping(value = "/lb")
public String gePaymentLb() {
return serverPost;
}
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# 2. 消费者
::details
@Bean
// @LoadBalanced 注释掉
public RestTemplate restTemplate() {
return new RestTemplate();
}
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接口
public interface loadBalancer {
/**
* 获取示例
*
* @param serviceInstances 服务进程信息
* @return 信息
*/
ServiceInstance instances(List<ServiceInstance> serviceInstances);
}
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实现类
/**
* @Author: CHGGX
* @Date: 2020/03/30 20:07
* @Description: <h1> 自定义ribbon轮询算法 </h1>
*/
@Component
public class MyLb implements loadBalancer {
private AtomicInteger atomicInteger = new AtomicInteger(0);
public final int getAndIncrement() {
int current;
int next;
do {
current = this.atomicInteger.get();
next = current >= 2147483647 ? 0 : current + 1;
} while (!this.atomicInteger.compareAndSet(current, next));
System.out.println("*****第几次访问,次数next: " + next);
return next;
}
@Override
public ServiceInstance instances(List<ServiceInstance> serviceInstances) {
// `rest 接口第几次请求数 % 服务器集群总数量 = 实际调用服务器位置下标`
//`每次服务器重启后rest接口数从1开始`
int index = getAndIncrement() % serviceInstances.size();
return serviceInstances.get(index);
}
public static void main(String[] args) {
// 2147483647
System.out.println(Integer.MAX_VALUE);
}
}
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controller
@Resource
private RestTemplate restTemplate;
@Resource
private loadBalancer loadBalancer;
@Resource
private DiscoveryClient discoveryClient;
/**
* 使用自定义的轮询算法,
*/
@GetMapping(value = "/lb")
public String getPaymentLb(){
List<ServiceInstance> instances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
if (instances==null || instances.size()<=0){
return null;
}
// 使用自定义
ServiceInstance serviceInstance = loadBalancer.instances(instances);
URI uri = serviceInstance.getUri();
return restTemplate.getForObject(uri+"/payment/lb",String.class);
}
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:::