Spring Boot Actuator 2 示例

Welcome file

简介

Spring Boot Actuator为应用程序提供了各种开箱即用的运维特性，可以与应用方便的交互和监控。

使用环境：Java 11 和 Spring Boot 2.4.3.RELEASE

集成Spring Boot Actuator

在Spring Boot中集成Spring Boot Actuator与集成其他的框架类似，在pom.xml里引入相关的starter就可以：

<dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-actuator</artifactId>
 </dependency>
<dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-web</artifactId>
</dependency>

由于大部分的使用场景还是web，所以这里也用Spring MVC做示例。

配置好pom.xml后，默认actuator仅暴露一些基本功能，实际使用中，根据需求暴露对应功能。为了简便测试，这里在application.yml中配置暴露全部功能：

management:
  endpoints:
    web:
      exposure:
        include: "*"
  endpoint:
    health:
      enabled: true
      show-details: always
      probes:
        enabled: true
    shutdown:
      enabled: true
  metrics:
    export:
      jmx:
        enabled: false
server:
  shutdown: graceful

之后启动程序，在控制台应该能看到以下输出：

2021-03-08 23:05:08.555  INFO 32637 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 16 endpoint(s) beneath base path '/actuator'

常用内置功能

Actuator内置了许多功能接口，下面介绍一些个人常用的。

查看缓存

/actuator/caches

这个接口能查看被Spring管理的缓存，依赖具体实现

查看环境

/actuator/env

这个接口能看到目前生效的环境参数

查看程序运行指标

/actuator/metrics

访问之后能得到目前可以查询的指标：

{"names":["http.server.requests","jvm.buffer.count","jvm.buffer.memory.used","jvm.buffer.total.capacity","jvm.classes.loaded","jvm.classes.unloaded","jvm.gc.live.data.size","jvm.gc.max.data.size","jvm.gc.memory.allocated","jvm.gc.memory.promoted","jvm.gc.pause","jvm.memory.committed","jvm.memory.max","jvm.memory.used","jvm.threads.daemon","jvm.threads.live","jvm.threads.peak","jvm.threads.states","logback.events","process.cpu.usage","process.files.max","process.files.open","process.start.time","process.uptime","running.demo.timer","system.cpu.count","system.cpu.usage","system.load.average.1m","tomcat.sessions.active.current","tomcat.sessions.active.max","tomcat.sessions.alive.max","tomcat.sessions.created","tomcat.sessions.expired","tomcat.sessions.rejected"]}

直接在url后加上对应的指标key能查询具体结果，比如：

/actuator/metrics/system.cpu.count

可以查看到结果：

{"name":"system.cpu.count","description":"The number of processors available to the Java virtual machine","baseUnit":null,"measurements":[{"statistic":"VALUE","value":12.0}],"availableTags":[]}

查看Request Mapping

/actuator/mappings

查看定时任务

/actuator/scheduledtasks

查看Thread dump

/actuator/threaddump

扩展内置功能

扩展HealthIndicator

定时的健康检查能及时发现应用中的问题，actuator默认提供了一系列内置的应用健康指标：

/actuator/health

访问之后可以看到结果：

{"status":"UP","components":{"diskSpace":{"status":"UP","details":{"total":999995129856,"free":965321064448,"threshold":10485760,"exists":true}},"livenessState":{"status":"UP"},"ping":{"status":"UP"},"readinessState":{"status":"UP"}},"groups":["liveness","readiness"]}

默认提供的是较为通用的健康指标，我们可以根据应用的特点，提供自定义的健康检查指标。比如对各种外部依赖的检查，应用内部状态的检查等。

假如应用对接了一个外部系统，我们可以扩展HealthIndicator来提供新的健康指标。扩展需要实现HealthIndicator接口，覆盖health()方法，并返回Health对象：

@Component
public class DemoHealthIndicator implements HealthIndicator {

    private static final HttpClient httpClient = HttpClient.newBuilder()
            .version(HttpClient.Version.HTTP_1_1)
            .connectTimeout(Duration.ofSeconds(10))
            .build();

    @Override
    public Health health() {
        return checkFooServiceHealth();
    }

    public Health checkFooServiceHealth(){
        try {
            HttpRequest request = HttpRequest.newBuilder()
                    .GET()
                    .uri(URI.create("https://start.spring.io/"))
                    .build();

            HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
            if (response.statusCode() == 200) {
                return Health.up()
                        .withDetail("statusCode", response.statusCode()).build();
            }
            return Health.down()
                    .withDetail("statusCode", response.statusCode()).build();
        } catch (Exception e) {
            return Health.unknown()
                    .withDetail("exception", e.getMessage()).build();
        }
    }
}

这时再访问health接口，可以看到返回结果已经加上了自定义的健康指标：

{"status":"UP","components":{"demo":{"status":"UP","details":{"statusCode":200}},"diskSpace":{"status":"UP","details":{"total":999995129856,"free":965321064448,"threshold":10485760,"exists":true}},"livenessState":{"status":"UP"},"ping":{"status":"UP"},"readinessState":{"status":"UP"}},"groups":["liveness","readiness"]}

扩展InfoContributor

Info接口主要提供应用程序相关信息，一般会放在当前运行版本中不会改变的信息。比如访问Elasticsearch，就会展示一串json，表示当前Elasticsearch的版本，构建时间等信息。在实际应用中，我们可以使用该接口提供开发者信息，应用名称，版本，git版本等信息。

自定义Info信息与上面类似，实现InfoContributor接口，覆盖contribute方法：

@Component
public class DemoInfo implements InfoContributor {

    @Value("${spring.application.name}")
    private String application;

    @Override
    public void contribute(Info.Builder builder) {
        builder.withDetail("application", application)
                .withDetail("git-version", "2d5fg23")
                .withDetail("version", "1.0-SNAPSHOT")
                .withDetail("dev", "Nereus Yi");
    }

}

为了演示简便，git-version、version信息直接写在代码里，实际应用中，可以通过读取根据maven构建信息来实现。

这时再访问info接口，

/actuator/info

可以看到返回结果已经加上了自定义的信息：

{"application":"actuator-demo","git-version":"2d5fg23","version":"1.0-SNAPSHOT","dev":"Nereus Yi"}

总结

本文展示了actuator的常用功能示例和一些扩展，示例工程可以在Github上找到。

参考资料

[1]https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-features.html

Yi

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