dropwizard metrics - healthchecks

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。

        <!-- metrics start -->
        <dependency>
            <groupId>io.dropwizard.metrics</groupId>
            <artifactId>metrics-core</artifactId>
            <version>${project-metricsVersion}</version>
        </dependency>
        <dependency>
            <groupId>io.dropwizard.metrics</groupId>
            <artifactId>metrics-healthchecks</artifactId>
            <version>${project-metricsVersion}</version>
        </dependency>
        <!-- metrics end -->

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
 *
 */
public class SystemHealthCheck implements Runnable{

    private static final Logger LOG = LoggerFactory.getLogger(SystemHealthCheck.class);

    private final static HealthCheckRegistry healthChecks = new HealthCheckRegistry();

    public static boolean registerToSysHealthCheck(final String name, final HealthCheck healthCheck){
        if(healthChecks.getNames().contains(name)){
            return false;
        }
        healthChecks.register(name, healthCheck);
        return true;
    }

    public void run(){
        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
 *
 */
public class DatabaseHealthCheck extends HealthCheck {

    private final static String HEALTHCHECKNAME = DatabaseHealthCheck.class.getSimpleName();

    private SessionFactory sessionFactory;


    public DatabaseHealthCheck(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }

    public DatabaseHealthCheck(){
        SystemHealthCheck.registerToSysHealthCheck(HEALTHCHECKNAME, this);
    }

    @Override
    public HealthCheck.Result check() throws Exception {
        if (!sessionFactory.isClosed()) {
            return HealthCheck.Result.healthy();
        } else {
            return HealthCheck.Result.unhealthy("sessionFactory is closed " + sessionFactory.getStatistics());
        }
    }

}