前言

在Spring Boot第一個版本發(fā)布的時候就有了，它為Spring Boot提供了一系列產(chǎn)品級的特性：監(jiān)控應(yīng)用程序，收集元數(shù)據(jù)，運行情況或者數(shù)據(jù)庫狀態(tài)等。

使用Spring Boot Actuator我們可以直接使用這些特性而不需要自己去實現(xiàn)，它是用HTTP或者JMX來和外界交互。

開始使用Spring Boot Actuator

要想使用Spring Boot Actuator，需要添加如下依賴：

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

開始使用Actuator

配好上面的依賴之后，我們使用下面的主程序入口就可以使用Actuator了：

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

啟動應(yīng)用程序，訪問//localhost:8080/actuator：

{"_links":{"self":{"href":"http://localhost:8080/actuator","templated":false},"health":{"href":"http://localhost:8080/actuator/health","templated":false},"health-path":{"href":"http://localhost:8080/actuator/health/{*path}","templated":true},"info":{"href":"http://localhost:8080/actuator/info","templated":false}}}

我們可以看到actuator默認開啟了兩個入口：/health和/info。

如果我們在配置文件里面這樣配置，則可以開啟actuator所有的入口：

management.endpoints.web.exposure.include=*

重啟應(yīng)用程序，再次訪問//localhost:8080/actuator：

{"_links":{"self":{"href":"http://localhost:8080/actuator","templated":false},"beans":{"href":"http://localhost:8080/actuator/beans","templated":false},"caches-cache":{"href":"http://localhost:8080/actuator/caches/{cache}","templated":true},"caches":{"href":"http://localhost:8080/actuator/caches","templated":false},"health":{"href":"http://localhost:8080/actuator/health","templated":false},"health-path":{"href":"http://localhost:8080/actuator/health/{*path}","templated":true},"info":{"href":"http://localhost:8080/actuator/info","templated":false},"conditions":{"href":"http://localhost:8080/actuator/conditions","templated":false},"configprops":{"href":"http://localhost:8080/actuator/configprops","templated":false},"env":{"href":"http://localhost:8080/actuator/env","templated":false},"env-toMatch":{"href":"http://localhost:8080/actuator/env/{toMatch}","templated":true},"loggers-name":{"href":"http://localhost:8080/actuator/loggers/{name}","templated":true},"loggers":{"href":"http://localhost:8080/actuator/loggers","templated":false},"heapdump":{"href":"http://localhost:8080/actuator/heapdump","templated":false},"threaddump":{"href":"http://localhost:8080/actuator/threaddump","templated":false},"metrics":{"href":"http://localhost:8080/actuator/metrics","templated":false},"metrics-requiredMetricName":{"href":"http://localhost:8080/actuator/metrics/{requiredMetricName}","templated":true},"scheduledtasks":{"href":"http://localhost:8080/actuator/scheduledtasks","templated":false},"mappings":{"href":"http://localhost:8080/actuator/mappings","templated":false}}}

我們可以看到actuator暴露的所有入口。

Health Indicators

Health入口是用來監(jiān)控組件的狀態(tài)的，通過上面的入口，我們可以看到Health的入口如下：

"health":{"href":"http://localhost:8080/actuator/health","templated":false},"health-path":{"href":"http://localhost:8080/actuator/health/{*path}","templated":true},

有兩個入口，一個是總體的health，一個是具體的health-path。

我們訪問一下//localhost:8080/actuator/health：

{"status":"UP"}

上面的結(jié)果實際上是隱藏了具體的信息，我們可以通過設(shè)置

management.endpoint.health.show-details=ALWAYS

來開啟詳情，開啟之后訪問如下：

{"status":"UP","components":{"db":{"status":"UP","details":{"database":"H2","result":1,"validationQuery":"SELECT 1"}},"diskSpace":{"status":"UP","details":{"total":250685575168,"free":12428898304,"threshold":10485760}},"ping":{"status":"UP"}}}

其中的components就是health-path,我們可以訪問具體的某一個components如//localhost:8080/actuator/health/db:

{"status":"UP","details":{"database":"H2","result":1,"validationQuery":"SELECT 1"}}

就可以看到具體某一個component的信息。

這些Health components的信息都是收集實現(xiàn)了HealthIndicator接口的bean來的。

我們看下怎么自定義HealthIndicator：

@Component
public class CustHealthIndicator implements HealthIndicator {
    @Override
    public Health health() {
        int errorCode = check(); // perform some specific health check
        if (errorCode != 0) {
            return Health.down()
                    .withDetail("Error Code", errorCode).build();
        }
        return Health.up().build();
    }
    public int check() {
        // Our logic to check health
        return 0;
    }
}

再次查看//localhost:8080/actuator/health， 我們會發(fā)現(xiàn)多了一個Cust的組件：

"components":{"cust":{"status":"UP"} }

在Spring Boot 2.X之后，Spring添加了React的支持，我們可以添加ReactiveHealthIndicator如下：

@Component
public class DownstreamServiceHealthIndicator implements ReactiveHealthIndicator {
    @Override
    public Mono<Health> health() {
        return checkDownstreamServiceHealth().onErrorResume(
                ex -> Mono.just(new Health.Builder().down(ex).build())
        );
    }
    private Mono<Health> checkDownstreamServiceHealth() {
        // we could use WebClient to check health reactively
        return Mono.just(new Health.Builder().up().build());
    }
}

再次查看//localhost:8080/actuator/health，可以看到又多了一個組件：

"downstreamService":{"status":"UP"}

/info 入口

info顯示了App的大概信息，默認情況下是空的。我們可以這樣自定義：

info.app.name=Spring Sample Application
info.app.description=This is my first spring boot application
info.app.version=1.0.0

查看：//localhost:8080/actuator/info

{"app":{"name":"Spring Sample Application","description":"This is my first spring boot application","version":"1.0.0"}}

/metrics入口

/metrics提供了JVM和操作系統(tǒng)的一些信息，我們看下metrics的目錄，訪問：//localhost:8080/actuator/metrics：

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

訪問其中具體的某一個組件如下//localhost:8080/actuator/metrics/jvm.memory.max：

{"name":"jvm.memory.max","description":"The maximum amount of memory in bytes that can be used for memory management","baseUnit":"bytes","measurements":[{"statistic":"VALUE","value":3.456106495E9}],"availableTags":[{"tag":"area","values":["heap","nonheap"]},{"tag":"id","values":["Compressed Class Space","PS Survivor Space","PS Old Gen","Metaspace","PS Eden Space","Code Cache"]}]}

Spring Boot 2.X 的metrics是通過Micrometer來實現(xiàn)的，Spring Boot會自動注冊MeterRegistry。 有關(guān)Micrometer和Spring Boot的結(jié)合使用我們會在后面的文章中詳細講解。

自定義Endpoint

Spring Boot的Endpoint也是可以自定義的：

@Component
@Endpoint(id = "features")
public class FeaturesEndpoint {
    private Map<String, String> features = new ConcurrentHashMap<>();
    @ReadOperation
    public Map<String, String> features() {
        return features;
    }
    @ReadOperation
    public String feature(@Selector String name) {
        return features.get(name);
    }
    @WriteOperation
    public void configureFeature(@Selector String name, String value) {
        features.put(name, value);
    }
    @DeleteOperation
    public void deleteFeature(@Selector String name) {
        features.remove(name);
    }
}

訪問//localhost:8080/actuator/， 我們會發(fā)現(xiàn)多了一個入口： //localhost:8080/actuator/features/ 。

上面的代碼中@ReadOperation對應(yīng)的是GET， @WriteOperation對應(yīng)的是PUT，@DeleteOperation對應(yīng)的是DELETE。

@Selector后面對應(yīng)的是路徑參數(shù)， 比如我們可以這樣調(diào)用configureFeature方法：

POST /actuator/features/abc HTTP/1.1
Host: localhost:8080
Content-Type: application/json
User-Agent: PostmanRuntime/7.18.0
Accept: */*
Cache-Control: no-cache
Postman-Token: dbb46150-9652-4a4a-95cb-3a68c9aa8544,8a033af4-c199-4232-953b-d22dad78c804
Host: localhost:8080
Accept-Encoding: gzip, deflate
Content-Length: 15
Connection: keep-alive
cache-control: no-cache
{"value":true}

注意，這里的請求BODY是以JSON形式提供的：

{"value":true}

請求URL：/actuator/features/abc 中的abc就是@Selector 中的 name。

我們再看一下GET請求：

//localhost:8080/actuator/features/

{"abc":"true"}

這個就是我們之前PUT進去的值。

擴展現(xiàn)有的Endpoints

我們可以使用@EndpointExtension （@EndpointWebExtension或者@EndpointJmxExtension）來實現(xiàn)對現(xiàn)有EndPoint的擴展：

@Component
@EndpointWebExtension(endpoint = InfoEndpoint.class)
public class InfoWebEndpointExtension {
    private InfoEndpoint delegate;
    // standard constructor
    @ReadOperation
    public WebEndpointResponse<Map> info() {
        Map<String, Object> info = this.delegate.info();
        Integer status = getStatus(info);
        return new WebEndpointResponse<>(info, status);
    }
    private Integer getStatus(Map<String, Object> info) {
        // return 5xx if this is a snapshot
        return 200;
    }
}

上面的例子擴展了InfoEndpoint。

到此這篇關(guān)于SpringBoot中的Actuator詳解的文章就介紹到這了,更多相關(guān)Actuator詳解內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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