Spring Cloud Alibaba体系使用OpenFeign与RestTemplate作为RPC组件

前言

本篇将介绍Spring Cloud Alibaba使用OpenFeign和RestTemplate进行RPC调用，并且将介绍两种RPC工具如何集成Sentinel进行系统保护。

OpenFeign

OpenFeign介绍

OpenFeign是一种声明式、模板化的HTTP客户端。在Spring Cloud中使用OpenFeign，可以做到使用HTTP请求访问远程服务，就像调用本地方法一样的，开发者完全感知不到这是在调用远程方法，更感知不到在访问HTTP请求。

OpenFeign使用

编写两个服务，一个provider服务account-svc一个consumer服务order-svc。

Provider代码

pom依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>io.redick.cloud</groupId><artifactId>ruuby-account</artifactId><version>${revision}</version></parent><artifactId>ruuby-account-svc</artifactId><packaging>jar</packaging><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency></dependencies>
</project>

application.yml配置

server:port: 8088
spring:application:name: account-svccloud:nacos:username: "nacos"password: "nacos"discovery:# 服务注册中心地址server-addr: 127.0.0.1:8848

服务端代码

@SpringBootApplication
@EnableDiscoveryClient
public class AccountApplication {public static void main( String[] args ) {SpringApplication.run(AccountApplication.class, args);}@GetMapping(path = "/echo/{string}")public String echo(@PathVariable String string) {return "Hello Nacos Discovery " + string;}
}

Consumer代码

pom依赖

对比之前的demo，增加了artifactId为spring-cloud-starter-openfeign的OpenFeign依赖。

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>io.redick.cloud</groupId><artifactId>ruuby-account</artifactId><version>${revision}</version></parent><artifactId>ruuby-account-svc</artifactId><packaging>jar</packaging><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-loadbalancer</artifactId></dependency><!-- OpenFeign --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency></dependencies>
</project>

application.yml配置

server:port: 8089
spring:application:name: order-svccloud:nacos:username: "nacos"password: "nacos"discovery:# 服务注册中心地址server-addr: 127.0.0.1:8848

服务启动代码

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients(basePackages = {"io.redick.cloud.account"})
@AllArgsConstructor
public class OrderApplication {private final AccountService accountService;public static void main(String[] args) {SpringApplication.run(OrderApplication.class, args);}@GetMapping("/echo")public String echo(){return accountService.echo(appName);}
}

在io.redick.cloud.account包下创建AccountService，@FeignClient注解标注这是一个OpenFeign客户端，可以看到OpenFeign屏蔽了底层Http调用细节，可以像调用一个本地方法一样去进行远程调用，并且参数的序列化，反序列化也屏蔽了，对于开发人员来说使用起来更方便。

注：OpenFeign+@PathVariable 需要指定value否则会报错

@FeignClient(name = "account-svc", path = "/account")
public interface AccountService {@GetMapping(path = "/echo/{string}")String echo(@PathVariable(value="string") String string);
}

测试

➜ curl -X GET http://127.0.0.1:8089/order/feignEcho
Hello Nacos Discovery order-svc

配置使用Nacos LoadBalancer

demo中没有配置LoadBalancer，因为引用了spring-cloud-starter-loadbalancer依赖，所以默认情况下使用spring-cloud-starter-loadbalancer的RoundRobinLoadBalancer负载均衡器。Nacos Discovery提供了NacosLoadBalancer，通过如下配置开启NacosLoadBalancer。

spring:cloud:loadbalancer:nacos:enabled: true

OpenFeign集成Sentinel

Spring Cloud Alibaba集成Sentinel引入spring-cloud-starter-alibaba-sentinel的starter，并且添加一些配置即可实现。

pom依赖

				<!-- SpringCloud Alibaba Sentinel --><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-sentinel</artifactId></dependency><!-- Sentinel Datasource Nacos --><dependency><groupId>com.alibaba.csp</groupId><artifactId>sentinel-datasource-nacos</artifactId></dependency>

application.yml配置

spring:cloud:# sentinel支持sentinel:# 取消控制台懒加载eager: truetransport:dashboard: 127.0.0.1:8080# 动态数据源支持datasource:ds1:nacos:server-addr: 127.0.0.1:8848dataId: ${spring.application.name}-sentinel-${spring.profiles.active}.jsonnamespace: 3ef5e608-6ee8-4881-8e50-ed47a5a04af2groupId: DEFAULT_GROUPdata-type: json# 具体配置参考com.alibaba.cloud.sentinel.datasource.RuleTyperule-type: flow
# feign支持sentinel
feign:sentinel:enabled: true

Nacos配置中心增加dataId为${spring.application.name}-sentinel-${spring.profiles.active}.json的配置文件，并配置流控规则，配置如下：

[{"resource": "GET:http://account-svc/account/echo/{string}","count": 0,"grade": 0,"limitApp": "default"}
]

OpenFeign自定义降级

public class AccountCallback implements AccountService {@Overridepublic String echo(String string) {return "Sentinel circuit breaker!";}
}public class FeignConfiguration {@Beanpublic AccountCallback accountCallback() {return new AccountCallback();}
}

AccountService @FeignClient标签增加自定义配置和自定义降级。

@FeignClient(name = "account-svc", path = "/account", fallback = AccountCallback.class,configuration = FeignConfiguration.class)
public interface AccountService {/*** 注：OpenFeign+@PathVariable 需要指定value否则会报错** @param string String* @return String*/@GetMapping(path = "/echo/{string}")String echo(@PathVariable(value="string") String string);
}

将Nacos上Sentinel配置count改为0，测试结果如下：

➜ curl -X GET http://127.0.0.1:8089/order/feignEcho
Sentinel circuit breaker!

RestTemplate

大部分代码参考上面的代码，下面是RestTemplate相关的配置代码，@LoadBalanced开启负载均衡，@SentinelRestTemplate是Sentinel注解，括号里的配置都是自定义降级，流控的配置。

创建RestTemplate Bean

@Configuration
public class RestTemplateConfiguration {@Bean@LoadBalanced@SentinelRestTemplate(blockHandler = "blockHandle", blockHandlerClass = SentinelHandleUtil.class,fallback = "fallback", fallbackClass = SentinelHandleUtil.class)public RestTemplate restTemplate() {RestTemplate restTemplate = new RestTemplate();// 链路追踪restTemplate.setInterceptors(Stream.of(new TraceIdRestTemplateInterceptor()).collect(Collectors.toList()));return restTemplate;}
}

自定义流控代码SentinelHandleUtil

public class SentinelHandleUtil {public static SentinelClientHttpResponse blockHandle(HttpRequest request, byte[] body, ClientHttpRequestExecution execution, BlockException exception) {return new SentinelClientHttpResponse(JSON.toJSONString(R.fail(null, Constants.FLOW, "Sentinel flow block!")));}public static SentinelClientHttpResponse fallback(HttpRequest request, byte[] body, ClientHttpRequestExecution execution, BlockException exception) {return new SentinelClientHttpResponse(JSON.toJSONString(R.fail(null, Constants.FLOW, "Sentinel flow block!")));}
}

application.yml配置开启Sentinel

# RestTemplate支持sentinel
resttemplate:sentinel:enabled: true

Nacos配置中心Sentinel配置文件增加配置

    {"resource": "GET:http://account-svc:8088/account/echo/order-svc","count": 0,"grade": 0,"limitApp": "default"}

测试结果

➜ curl -X GET http://127.0.0.1:8089/order/echo
{"code":455,"msg":"Sentinel flow block!"}

总结

致此Spring Cloud Alibaba集成OpenFeign，RestTemplate作为RPC，Spring Cloud LoadBalancer，NacosLoadBalancer作为负载均衡，Sentinel作为系统保护介绍完毕，相关底层逻辑感兴趣的可以自行Debug一下代码。

源码参考GitHub，如果对您有帮助麻烦点个赞支持下，谢谢！