跟我學Spring Cloud（Finchley版）-03-監控：強大的Boot Actuator

第2節（ 跟我學Spring Cloud（Finchley版）-02-構建分布式應用 ）說過：

應用沒有監控，沒有畫板，一切指標都沒有。在這個Growth Hack逐漸成為主流的時代，不弄個Dashboard把系統壓力、QPS、CPU、內存、日活啥的可視化，你好意思出來混嗎……

本節我們來解決該問題。

Spring Boot Actuator是Spring Boot官方提供的監控組件。只需為項目添加以下依賴，即可就整合Spring Boot Actuator。

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

監控端點

Actuator為我們提供了很多監控端點，如下表所示。

表-Spring Boot Actuator常用端點及描述

只需訪問http://{ip}:{port}/actuator/{endpoint} 端點，即可監控應用的運行狀況。

測試1：/health端點

為前文編寫的microservice-simple-provider-user 服務整合Actuator后，我們來做一些測試：

訪問<http://localhost:8000/actuator/health> ，即可獲得如下結果：

{"status":"UP"}

測試2：/health端點展示詳情

為/health 端點配置顯示詳情：

management:
  endpoint:
    health:
      # 是否展示健康檢查詳情
      show-details: always

再次訪問<http://localhost:8000/actuator/health> ，即可獲得如下結果：

{
    "status": "UP",
    "details": {
        "db": {
            "status": "UP",
            "details": {
                "database": "H2",
                "hello": 1
            }
        },
        "diskSpace": {
            "status": "UP",
            "details": {
                "total": 250790436864,
                "free": 43443773440,
                "threshold": 10485760
            }
        }
    }
}

從中可以看到，/health 端點展示了DB的健康情況以及磁盤的健康情況。

測試3：暴露敏感路徑

默認情況下，敏感路徑并不暴露。如需暴露（以metrics為例），需添加配置：

management:
  endpoints:
    web:
      exposure:
        # 暴露metrics端點，如需暴露多個，用,分隔；如需暴露所有端點，用'*'
        include: metrics

訪問：<http://localhost:8000/actuator/metrics> ，可獲得類似如下的結果：

{
    "names": ["jvm.memory.max", "http.server.requests", "jdbc.connections.active", "process.files.max", "jvm.gc.memory.promoted", "tomcat.cache.hit", "system.load.average.1m", "tomcat.cache.access", "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", "tomcat.global.sent", "jvm.buffer.memory.used", "tomcat.sessions.created", "jvm.threads.daemon", "system.cpu.usage", "jvm.gc.memory.allocated", "tomcat.global.request.max", "hikaricp.connections.idle", "hikaricp.connections.pending", "tomcat.global.request", "tomcat.sessions.expired", "hikaricp.connections", "jvm.threads.live", "jvm.threads.peak", "tomcat.global.received", "hikaricp.connections.active", "hikaricp.connections.creation", "process.uptime", "tomcat.sessions.rejected", "process.cpu.usage", "tomcat.threads.config.max", "jvm.classes.loaded", "hikaricp.connections.max", "hikaricp.connections.min", "jvm.classes.unloaded", "tomcat.global.error", "tomcat.sessions.active.current", "tomcat.sessions.alive.max", "jvm.gc.live.data.size", "tomcat.servlet.request.max", "hikaricp.connections.usage", "tomcat.threads.current", "tomcat.servlet.request", "hikaricp.connections.timeout", "process.files.open", "jvm.buffer.count", "jvm.buffer.total.capacity", "tomcat.sessions.active.max", "hikaricp.connections.acquire", "tomcat.threads.busy", "process.start.time", "tomcat.servlet.error"]
}

訪問http://localhost:8000/actuator/metrics/{name} ，{name} 列表如上，即可查看當前應用的度量指標。例如訪問：<http://localhost:8000/actuator/metrics/jvm.memory.max> 即可查看JVM可管理的最大內存，結果類似如下：

{
    "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": 5.597298687E9
    }],
    "availableTags": [{
        "tag": "area",
        "values": ["heap", "nonheap"]
    }, {
        "tag": "id",
        "values": ["Compressed Class Space", "PS Survivor Space", "PS Old Gen", "Metaspace", "PS Eden Space", "Code Cache"]
    }]
}

TIPS

• 如需暴露所有監控端點可配置：

  management:
  endpoints:
    web:
      exposure:
        include: '*'

• 有關Spring Boot 1.x與2.x端點的差異，詳見：<https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.0-Migration-Guide#endpoints>

拓展閱讀

如果能對Actuator端點的文字數據進行圖形化的展示，我們就可以實現比較低層次的“Growth Hack”啦！開源界已經有這樣的工具——Spring Boot Admin ，界面如下。有興趣的可前往<https://github.com/codecentric/spring-boot-admin>了解。

說明

• 由于Actuator本身是Spring Boot中的組件，并不是本套教程的重點（其實筆者本不想寫這一節，但后面又會持續用這些端點，并且Spring Cloud在這些端點的基礎上還做了一些增加，所以還是有必要介紹一下），因此本節只是對Actuator進行了比較簡單的介紹，讀者可自行挖掘Actuator的其他能力。也可持續關注本公眾號，本系列完成后，筆者將會扒開Actuator的底褲，深度介紹Spring Boot監控的那些事兒。

配套代碼

GitHub：

• https://github.com/eacdy/spring-cloud-study/tree/master/2018-Finchley/microservice-simple-provider-user
• https://github.com/eacdy/spring-cloud-study/tree/master/2018-Finchley/microservice-simple-consumer-movie

Gitee：

• https://gitee.com/itmuch/spring-cloud-study/tree/master/2018-Finchley/microservice-simple-provider-user
• https://gitee.com/itmuch/spring-cloud-study/tree/master/2018-Finchley/microservice-simple-consumer-movie

原文：http://www.itmuch.com/spring-cloud/finchley-3/ ，轉載請說明出處。

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