前言
完整知識點:spring cloud netflix 系列技術棧
在spring cloud netflix中使用ribbon和feign作爲服務與服務之間的通信機制,這種通信方式是同步的HTTP通信方式,在大訪問量的情況下會發生阻塞,直觀體現就是標籤頁一直在等待響應,這就會有一個響應時間。而熔斷器的作用就是:在發現服務不可用時,立即做出反應,避免請求一直處於等待響應的狀態,從而避免出現響應時間,減輕服務器壓力,避免出現雪崩。
- 沒有熔斷器,響應處於等待狀態
- 使用熔斷器,發現服務不可用,立即做出反應,避免等待(阻塞)
Hystrix熔斷器
通過在前言中的理解,我們知道了熔斷器的作用是:當服務與服務之間的通信出現問題時,熔斷器會立即做出響應,避免發生阻塞。
Hystrix + Feign
- Hystrix的pom依賴
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
- 完整的pom依賴
<?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>
<!-- 關聯統一的依賴管理 -->
<parent>
<groupId>com.baiyang</groupId>
<artifactId>spring-cloud-netflix-dependencies</artifactId>
<version>1.0.0-SNAPSHOT</version>
<!-- 指向統一的依賴管理的位置 -->
<relativePath>../spring-cloud-netflix-dependencies/pom.xml</relativePath>
</parent>
<groupId>com.baiyang</groupId>
<artifactId>spring-cloud-netflix-web-admin-feign</artifactId>
<packaging>jar</packaging>
<dependencies>
<!-- Spring Boot Begin -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!-- Spring Boot End -->
<!-- Spring Cloud Begin -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
</dependency>
<!-- Spring Cloud End -->
<!-- 解決 thymeleaf 模板引擎一定要執行嚴格的 html5 格式校驗問題 -->
<dependency>
<groupId>net.sourceforge.nekohtml</groupId>
<artifactId>nekohtml</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<!-- 配置程序的入口類 -->
<mainClass>com.baiyang.spring.cloud.netflix.web.admin.feign.AdminWebFeignApplication</mainClass>
</configuration>
</plugin>
</plugins>
</build>
</project>
- Feign默認集成了Hystrix,在application.yml中開啓即可
spring:
application:
name: spring-cloud-netflix-web-admin-feign
server:
port: 8765
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8761/eureka/
# Feign默認集成了Hystrix
feign:
hystrix:
enabled: true
thymeleaf:
cache: false
mode: LEGACYHTML5
encoding: UTF-8
servlet:
content-type: text/html
- 在feign模式下,熔斷機制是通過實現需要被熔斷的接口來實現熔斷機制的,也就是說,在接口實現類中完成熔斷機制
1:實現需要被熔斷的接口
package com.baiyang.spring.cloud.netflix.web.admin.feign.service.hystrix;
import com.baiyang.spring.cloud.netflix.web.admin.feign.service.AdminFeignService;
import org.springframework.stereotype.Component;
@Component
public class AdminFeignServiceHystrix implements AdminFeignService {
@Override
public String hello(String message) {
return String.format("您輸入的信息是 %s , 但是請求失敗。", message);
}
}
2:在接口中調用熔斷機制
package com.baiyang.spring.cloud.netflix.web.admin.feign.service;
import com.baiyang.spring.cloud.netflix.web.admin.feign.service.hystrix.AdminFeignServiceHystrix;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
@FeignClient(value = "spring-cloud-netflix-server-admin",fallback = AdminFeignServiceHystrix.class)
public interface AdminFeignService {
@GetMapping("hello")
String hello(@RequestParam(value = "message")String message);
}