預設情況下注冊到eureka server的服務是通過心跳來告知自己是UP還是DOWN，並不是通過spring-boot-actuator模組的/health端點來實現的，這樣其實不是很合理。

預設的心跳實現方式可以有效的檢查eureka客戶端程序是否正常運作，但是無法保證客戶端應用能夠正常提供服務。由於大多數微服務應用都會有一些其他的外部資源依賴，比如資料庫，REDIS快取等，如果我們的應用與這些外部資源無法連通的時候，實際上已經不能提供正常的對外服務了，但因為客戶端心跳依然在執行，所以它還是會被服務消費者呼叫，而這樣的呼叫實際上並不能獲得預期的後果。

我們可以通過在eureka客戶端中配置:eureka.client.healthcheck.enabled=true，就可以改變eureka server對客戶端健康檢測的方式，改用actuator的/health端點來檢測。

我們在前面的ribbon consumer樣例工程中新增一個自定義的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) //自定義監控內容
                    .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;
    }
}
 

裡面有一個成員變數up，用來控制是否監控，下面我們會在請求中改變這個變數的值來模擬健康狀態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();
    }



}
 

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端點來代替心跳錶明服務是否可用，反應到eureka server ui上服務的UP還是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}}}

啟動類:

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);
    }
}

<?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>

啟動該服務將會註冊到eureka server中去，此時顯示的應該是UP

然後我們呼叫一下服務:http://localhost:8200/up?up=false，將此時檢視http://localhost:8200/health,整個應用的health狀態變成DOWN了：

註冊中心的服務狀態也將變為DOWN：

我們可以試一下把application.yml中eureka.client.healthcheck.enabled=true這段配置去掉重新啟動服務，然後呼叫服務將health變為DOWN,但是註冊中心中仍然會顯示該服務的status為UP！