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149 lines
5.3 KiB
Markdown
149 lines
5.3 KiB
Markdown
# Sentinel Dubbo Example
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## 项目说明
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本项目演示如何使用 Sentinel starter 完成 Dubbo 应用的限流管理。
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[Sentinel](https://github.com/alibaba/Sentinel) 是阿里巴巴开源的分布式系统的流量防卫组件，Sentinel 把流量作为切入点，从流量控制，熔断降级，系统负载保护等多个维度保护服务的稳定性。
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[Dubbo](http://dubbo.apache.org/)是一款高性能Java RPC框架，有对应的[SpringBoot工程](https://github.com/apache/dubbo-spring-boot-project)。
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本项目专注于Sentinel与Dubbo的整合，关于Sentinel的更多特性可以查看[sentinel-core-example](https://github.com/alibaba/spring-cloud-alibaba/tree/master/spring-cloud-alibaba-examples/sentinel-example/sentinel-core-example)。
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## 示例
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### 如何接入
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在启动示例进行演示之前，我们先了解一下 Dubbo 如何接入 Sentinel。
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**注意 本章节只是为了便于您理解接入方式，本示例代码中已经完成接入工作，您无需再进行修改。**
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1. 首先，修改 pom.xml 文件，引入 Sentinel starter 和 Dubbo starter。
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<dependency>
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<groupId>com.alibaba.cloud</groupId>
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<artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
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</dependency>
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<dependency>
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<groupId>com.alibaba.boot</groupId>
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<artifactId>dubbo-spring-boot-starter</artifactId>
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</dependency>
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2. 配置限流规则
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Sentinel提供了[sentinel-dubbo-adapter](https://github.com/alibaba/Sentinel/tree/master/sentinel-adapter/sentinel-dubbo-adapter)模块用来支持Dubbo服务调用的限流降级。sentinel-starter默认也集成了该功能。
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sentinel-dubbo-adapter内部的Dubbo Filter会根据资源名进行限流降级处理。只需要配置规则即可：
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FlowRule flowRule = new FlowRule();
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flowRule.setResource("dubboResource");
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flowRule.setCount(10);
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flowRule.setGrade(RuleConstant.FLOW_GRADE_QPS);
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flowRule.setLimitApp("default");
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FlowRuleManager.loadRules(Collections.singletonList(flowRule));
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### 服务定义及发布
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Provider端在application.properties文件中定义dubbo相关的配置，比如协议，注册中心：
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spring.application.name = dubbo-provider-demo
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foo.service.version = 1.0.0
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dubbo.scan.basePackages = com.alibaba.cloud.examples
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dubbo.application.id = dubbo-provider-demo
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dubbo.application.name = dubbo-provider-demo
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dubbo.protocol.id = dubbo
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dubbo.protocol.name = dubbo
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dubbo.protocol.port = 12345
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dubbo.protocol.status = server
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dubbo.registry.id = my-registry
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dubbo.registry.address = N/A
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`sentinel-dubbo-api`模块中定义了FooService服务，内容如下：
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package com.alibaba.cloud.examples;
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public interface FooService {
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String hello(String name);
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}
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定义具体的服务：
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@Service(
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version = "${foo.service.version}",
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application = "${dubbo.application.id}",
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protocol = "${dubbo.protocol.id}",
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registry = "${dubbo.registry.id}"
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)
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public class FooServiceImpl implements FooService {
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@Override
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public String hello(String name) {
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return "hello, " + name;
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}
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}
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### 服务调用
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Consumer端在服务调用之前，先定义限流规则。
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`sentinel-dubbo-api`模块中定义了FooService服务，内容如下：
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package com.alibaba.cloud.examples;
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public interface FooService {
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String hello(String name);
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}
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该服务在Sentinel下对应的资源名是 `com.alibaba.cloud.examples.FooService:hello(java.lang.String)` 。
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定义该资源名对应的限流规则：
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FlowRule flowRule = new FlowRule();
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flowRule.setResource("com.alibaba.cloud.examples.FooService:hello(java.lang.String)");
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flowRule.setCount(10);
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flowRule.setGrade(RuleConstant.FLOW_GRADE_QPS);
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flowRule.setLimitApp("default");
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FlowRuleManager.loadRules(Collections.singletonList(flowRule));
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根据Provider端中发布的定义，使用Dubbo的@Reference注解注入服务对应的Bean：
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@Reference(version = "${foo.service.version}", application = "${dubbo.application.id}",
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path = "dubbo://localhost:12345", timeout = 30000)
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private FooService fooService;
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由于设置的qps是10。调用15次查看是否被限流：
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FooServiceConsumer service = applicationContext.getBean(FooServiceConsumer.class);
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for (int i = 0; i < 15; i++) {
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try {
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String message = service.hello("Jim");
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System.out.println((i + 1) + " -> Success: " + message);
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}
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catch (SentinelRpcException ex) {
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System.out.println("Blocked");
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}
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catch (Exception ex) {
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ex.printStackTrace();
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}
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}
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### 应用启动
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支持 IDE 直接启动和编译打包后启动。
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Provider端：
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1. IDE直接启动：找到主类 `SentinelDubboProviderApp`，执行 main 方法启动应用。
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2. 打包编译后启动：首先执行 `mvn clean package` 将工程编译打包，然后执行 `java -jar sentinel-dubbo-provider-example.jar`启动应用。
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Consumer端：
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1. IDE直接启动：找到主类 `SentinelDubboConsumerApp`，执行 main 方法启动应用。
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2. 打包编译后启动：首先执行 `mvn clean package` 将工程编译打包，然后执行 `java -jar sentinel-dubbo-consumer-example.jar`启动应用。
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