改变eureka server中注册的服务的健康检测方式

默认情况下注册到eureka server的服务是通过心跳来告知自己是UP还是DOWN，并不是通过spring-boot-actuator模块的/health端点来实现的，这样其实不是很合理。

默认的心跳实现方式可以有效的检查eureka客户端进程是否正常运作，但是无法保证客户端应用能够正常提供服务。由于大多数微服务应用都会有一些其他的外部资源依赖，比如数据库，REDIS缓存等，如果我们的应用与这些外部资源无法连通的时候，实际上已经不能提供正常的对外服务了，但因为客户端心跳依然在运行，所以它还是会被服务消费者调用，而这样的调用实际上并不能获得预期的后果。

我们可以通过在eureka客户端中配置:eureka.client.healthcheck.enabled=true，就可以改变eureka server对客户端健康检测的方式，改用actuator的/health端点来检测。

我们在前面的ribbon consumer样例工程中添加一个自定义的HealthIndicator:

package com.example.eurekaclientconsumerribbon.health;

import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;

@Component
public class MyHealthChecker implements HealthIndicator {

private boolean up = true;

@Override
public Health health() {
if (up) {
return new Health.Builder().withDetail("aaa_cnt", 10) //自定义监控内容
.withDetail("bbb_status", "up").up().build();
} else {
return new Health.Builder().withDetail("error", "client is down").down().build();
}

}

public boolean isUp() {
return up;
}

public void setUp(boolean up) {
this.up = up;
}
}


里面有一个成员变量up，用来控制是否监控，下面我们会在请求中改变这个变量的值来模拟健康状态UP->DOWN

package com.example.eurekaclientconsumerribbon.controller;

import com.example.eurekaclientconsumerribbon.health.MyHealthChecker;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UpController {

@Autowired
MyHealthChecker myHealthChecker;

@RequestMapping("/up")
public String up(@RequestParam("up") Boolean up) {
myHealthChecker.setUp(up);

return up.toString();
}

}


application.yml:
spring:
application:
name: eureka-client-consumer-ribbon
management:
security:
enabled: false
---
spring:
profiles: peer1
server:
port: 8200
eureka:
client:
serviceUrl:
defaultZone: http://peer1:8001/eureka/,http://peer2:8002/eureka/ healthcheck:
enabled: true #使用health端点来代替心跳表明服务是否可用，反应到eureka server ui上服务的UP还是DOWN
instance:
hostname: peer1
# instanceId: ${spring.application.name}:${vcap.application.instance_id:${spring.application.instance_id:${random.value}}}

---
spring:
profiles: peer2
server:
port: 8201
eureka:
client:
serviceUrl:
defaultZone: http://peer1:8001/eureka/,http://peer2:8002/eureka/ instance:
hostname: peer2
# instanceId: ${spring.application.name}:${vcap.application.instance_id:${spring.application.instance_id:${random.value}}}



主要看配置里面设置了eureka.client.healthcheck.enabled=true，这个配置属性在IDEA里面不会自动提示，我一度怀疑写错了，试过确实有效的改变了检测方式。
启动类:

package com.example.eurekaclientconsumerribbon;

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.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableEurekaClient
@EnableCircuitBreaker
@EnableHystrixDashboard
public class EurekaClientConsumerRibbonApplication {

@LoadBalanced
@Bean
RestTemplate restTemplate() {
return new RestTemplate();
}

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


pom:
<?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>

<groupId>com.example</groupId>
<artifactId>eureka-client-consumer-ribbon</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>eureka-client-consumer-ribbon</name>
<description>Demo project for Spring Boot</description>

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.6.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>

<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
<spring-cloud.version>Dalston.SR3</spring-cloud.version>
</properties>

<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.jolokia</groupId>
<artifactId>jolokia-core</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</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>
<executions>
<execution>
<goals>
<goal>build-info</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

</project>


启动该服务将会注册到eureka server中去，此时显示的应该是UP



然后我们调用一下服务:http://localhost:8200/up?up=false，将此时查看http://localhost:8200/health,整个应用的health状态变成DOWN了：



注册中心的服务状态也将变为DOWN：



我们可以试一下把application.yml中eureka.client.healthcheck.enabled=true这段配置去掉重新启动服务，然后调用服务将health变为DOWN,但是注册中心中仍然会显示该服务的status为UP！