spring cloud开发Greenwich版：断路器（六）

|

前面的文章主要探索的是微服务通信及服务发现（Communication and Discovery），接下来要解决的是容错及故障恢复（Fault Tolerance and Resilience）
当某个微服务出现故障时，确保系统能够正常运行及从故障中恢复
spring cloud采用了一种称之为断路器（Circuit breaker）的模式，本文主要演示该模式的Hystrix实现

这里是基于微服务’ralab-client’

  • Add the Maven spring-cloud-starter-netflix-hystrix denpendency
  • Add @EnableCircuitBreaker to the application class
  • Add @HystrixCommand to methods that need circuit breakers
  • configure Hystrix behavior
    其pom.xml文件如下： 
    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23
    24
    25
    26
    27
    28
    29
    30
    31
    32
    33
    34
    35
    36
    37
    38
    39
    40
    41
    42
    43
    44
    45
    46
    47
    48
    49
    50
    51
    52
    53
    54
    55
    56
    57
    58
    59
    60
    61
    62
    63
    64
    65
    <?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
        <modelVersion>4.0.0</modelVersion>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.8.RELEASE</version>
            <relativePath/> <!-- lookup parent from repository -->
        </parent>
        <groupId>com.ralab</groupId>
        <artifactId>ralab-client</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>ralab-client</name>
        <description>Demo project for Spring Boot</description>

        <properties>
            <java.version>1.8</java.version>
            <spring-cloud.version>Greenwich.SR2</spring-cloud.version>
        </properties>

        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            </dependency>

            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            </dependency>

            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>

        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>${spring-cloud.version}</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>

        <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
            </plugins>
        </build>

    </project>

RalabClientApplication文件

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
package com.ralab.ralabclient;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
public class RalabClientApplication {

    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate()
    {
        return new RestTemplate();
    }

    public static void main(String[] args) {
        SpringApplication.run(RalabClientApplication.class, args);
    }

}

NlpResource文件

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
package com.ralab.ralabclient.resources;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@RequestMapping("/nlp")
public class NlpResource {

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/service")
    @HystrixCommand(fallbackMethod = "getFallbackIndex")
    public String index()
    {
      //String result = restTemplate.getForObject("http://localhost:8090/nlp/api", String.class);
      String result = restTemplate.getForObject("http://nlp-service/nlp/api", String.class);
      return result;
    }

    private String getFallbackIndex()
    {
        //String result = restTemplate.getForObject("http://localhost:8090/nlp/api", String.class);

        return "不好意思，没有获取到服务端信息";
    }
}

先停止微服务’ralab-nlp’，重新运行RalabClientApplication，测试http://localhost:8091/nlp/service

上面利用Hystrix实现了微服务’ralab-client’的容错及故障恢复功能，在其需要容错的方法上，还可以自定义相关参数，这里不再演示

坚持原创技术分享，您的支持是我前进的动力！