cloud的技术积累

系统监控一直都是很重要的内容，可以让应用主动通知你系统现在的允许状况。Java世界里面dropwizard提供了系统监控的功能，个人觉得非常好用，，主要分为2大块，一块是系统健康监控，一块是系统的运行度量统计。第一篇先介绍健康依赖。 首先在pom文件中加入metrics健康监控包依赖。

>io.dropwizard.metrics>${project-metricsVersion}>>${project-metricsVersion}

其次创建健康检查的Scheduled task服务，通过scheduled task把健康信息发送到监控平台，也可以简单记录文件，连续几次不健康后邮件短信通知，现在展示一种简单实现（通过Logger单纯记录健康状态到文件）：

/** * */package com.cloud.demo.service.impl;import java.util.Map;import java.util.Map.Entry;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import com.codahale.metrics.health.HealthCheck;import com.codahale.metrics.health.HealthCheck.Result;import com.codahale.metrics.health.HealthCheckRegistry;/** * @author cloudlu * */{Logger LOG = LoggerFactory.getLogger(SystemHealthCheck.class);HealthCheckRegistry healthChecks = new HealthCheckRegistry();(final String name, final HealthCheck healthCheck){if(healthChecks.getNames().contains(name)){return false;}healthChecks.register(name, healthCheck);return true;}(){final Map<String, Result> results = healthChecks.runHealthChecks();StringBuilder message = null;for (Entry<String, Result> entry : results.entrySet()) {message = new StringBuilder(entry.getKey());if (entry.getValue().isHealthy()) {message.append(” is healthy: “).append(entry.getValue().getMessage());LOG.info(message.toString());} else {message.append(” is UNHEALTHY: “).append(entry.getValue().getMessage());LOG.error(message.toString(), entry.getValue().getError());}}}}

最后把要监控的系统注册到健康服务，并且提供指定回调函数，显示系统状态，例如查看hibernate的sessionfactory状态如下：

/** * */package com.cloud.demo.service.impl;import javax.annotation.Resource;import org.hibernate.SessionFactory;import org.springframework.orm.jpa.vendor.Database;import com.codahale.metrics.health.HealthCheck;/** * @author cloudlu * */{String HEALTHCHECKNAME = DatabaseHealthCheck.class.getSimpleName();private SessionFactory sessionFactory;public DatabaseHealthCheck(SessionFactory sessionFactory) {this.sessionFactory = sessionFactory;}public DatabaseHealthCheck(){SystemHealthCheck.registerToSysHealthCheck(HEALTHCHECKNAME, this);}@Overridepublic HealthCheck.Result check() throws Exception {if (!sessionFactory.isClosed()) {return HealthCheck.Result.healthy();} else {return HealthCheck.Result.unhealthy(“sessionFactory is closed ” + sessionFactory.getStatistics());}}}

世界上那些最容易的事情中，拖延时间最不费力。