当我们用K8S 部署微服务时， 很多时候需要调用 service的/health 等状态接口， 已确定container的运行状态是否健康。

而Spring boot Actuator 就是用来快速构造这些状态接口的工具

引入依赖

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

启用/health 和 /info 接口

management:endpoints:web:exposure:include: "info, health, loggers, env"base-path: /actuator

所有的接口介绍可以参考：
https://www.baeldung.com/spring-boot-actuators

/auditevents lists security audit-related events such as user login/logout. Also, we can filter by principal or type among other fields.
/beans returns all available beans in our BeanFactory. Unlike /auditevents, it doesn’t support filtering.
/conditions, formerly known as /autoconfig, builds a report of conditions around autoconfiguration.
/configprops allows us to fetch all @ConfigurationProperties beans.
/env returns the current environment properties. Additionally, we can retrieve single properties.
/flyway provides details about our Flyway database migrations.
/health summarizes the health status of our application.
/heapdump builds and returns a heap dump from the JVM used by our application.
/info returns general information. It might be custom data, build information or details about the latest commit.
/liquibase behaves like /flyway but for Liquibase.
/logfile returns ordinary application logs.
/loggers enables us to query and modify the logging level of our application.
/metrics details metrics of our application. This might include generic metrics as well as custom ones.
/prometheus returns metrics like the previous one, but formatted to work with a Prometheus server.
/scheduledtasks provides details about every scheduled task within our application.
/sessions lists HTTP sessions, given we are using Spring Session.
/shutdown performs a graceful shutdown of the application.
/threaddump dumps the thread information of the underlying JVM.

配置/health 接口的具体输出信息

默认/health 只会输出 status up or down, 如下

[gateman@manjaro-x13 ~]$ curl 127.0.0.1:8080/actuator/health
{"status":"UP"}

当我们在application.yml 加上下面配置后。

management:endpoint:health:show-details: always

会令到 /health 接口输出额外的components 信息：

{"status": "UP","components": {"diskSpace": {"status": "UP","details": {"total": 1038214316032,"free": 840063606784,"threshold": 10485760,"exists": true}},"ping": {"status": "UP"}}
}

这时， 我们可以额外 地从/health 接口知道ping 和 磁盘使用的信息。

其实 只要ping 和 diskSpace的状态任何1个status 为down, 这个/health的总status 就是down

但是通常来讲， 只考虑这两个子状态是不足够的。

增加BigQuery conneciton 状态

举个例子， 假如某个service 里面连接bigQuery, 我们需要在/health 接口加1个component ， 去detect BQ 的connection 是否健康。 如果这个BQ connection 为Down, 则/health status 为down

增加1个类 for checking the BQ connection

@Component
@Slf4j
public class BigQueryHealthCheck {@Autowiredprivate BigQuery bigQuery;public boolean isBigQueryHealthy() {CompletableFuture<Boolean> future = CompletableFuture.supplyAsync(() -> {try {bigQuery.listDatasets();return true;} catch (Exception e) {log.error("Error in BigQueryHealthCheck...", e);return false;}});try {// set time out to 5 seconds,  to wait for the return of future object.return future.get(5, TimeUnit.SECONDS);} catch (InterruptedException | ExecutionException | TimeoutException e) {log.error("Timeout or error while checking BigQuery connection", e);return false;}}
}

这里使用了CompletableFuture 类来设置1个5秒 timeout, 只要5秒内连不上BQ, 则认为BQ connection down

再增加1个类 for 增加1个BQ connection component to /health 接口

@Component
public class BQHealthIndicator extends AbstractHealthIndicator {@Autowiredprivate BigQueryHealthCheck bigQueryHealthCheck;@Overrideprotected void doHealthCheck(Health.Builder builder) throws Exception {if (bigQueryHealthCheck.isBigQueryHealthy()) {//int i=1/0;builder.up();} else {builder.down();}}
}

注意这个类必须是1个bean, 而且类名的suffix 是 HealthIndicator

这样， 当我们再次测试/health 接口时， 就包括BQ connection的监测了！

{"status": "UP","components": {"BQ": {"status": "UP"},"diskSpace": {"status": "UP","details": {"total": 1038214316032,"free": 839953145856,"threshold": 10485760,"exists": true}},"ping": {"status": "UP"}}
}

配置/info 接口的具体输出信息

默认下 /info 接口是什么信息都没有输出的，只有1个空的对象{}

如果我们想把service name, version 等信息写进info 接口， 也不复杂。

把pom.xml 的version 写入application.yml

在spring boot 中， 获取pom.xml 里面的具体字段值没有那么简单。
相对地， 从application.yml 获取configuration item的值是很容易的。

幸运地， 有1个方法可以把pom.xml 的内容写入application.yml

pom:version: @project.version@

在application yml里加入上面两行即可

添加1个类for /info的信息输出

@Component
public class AppVersionInfo implements InfoContributor {@Autowiredprivate Environment environment;@Value("${pom.version}") // https://stackoverflow.com/questions/3697449/retrieve-version-from-maven-pom-xml-in-codeprivate String appVersion;@Overridepublic void contribute(Info.Builder builder) {builder.withDetail("app", "Sales API").withDetail("version", appVersion).withDetail("description", "This is a simple Spring Boot application to demonstrate the use of BigQuery in GCP.");}
}

效果：

{"app": "Sales API","version": "1.0-SNAPSHOT","description": "This is a simple Spring Boot application to demonstrate the use of BigQuery in GCP."
}

就是甘简单