Metrics-Java版的指标度量工具之二

接上《Metrics-Java版的指标度量工具之一》

4.       Histograms

Histograms主要使用来统计数据的分布情况，最大值、最小值、平均值、中位数，百分比（75%、90%、95%、98%、99%和99.9%）。例如，需要统计某个页面的请求响应时间分布情况，可以使用该种类型的Metrics进行统计。具体的样例代码如下：

package com.netease.test.metrics;

import com.codahale.metrics.ConsoleReporter;
import com.codahale.metrics.Histogram;
import com.codahale.metrics.MetricRegistry;

import java.util.Random;
import java.util.concurrent.TimeUnit;

import static com.codahale.metrics.MetricRegistry.name;

/**
 * User: hzwangxx
 * Date: 14-2-17
 * Time: 18:34
 * 测试Histograms
 */
public class TestHistograms {
    /**
     * 实例化一个registry，最核心的一个模块，相当于一个应用程序的metrics系统的容器，维护一个Map
     */
    private static final MetricRegistry metrics = new MetricRegistry();

    /**
     * 在控制台上打印输出
     */
    private static ConsoleReporter reporter = ConsoleReporter.forRegistry(metrics).build();

    /**
     * 实例化一个Histograms
     */
    private static final Histogram randomNums = metrics.histogram(name(TestHistograms.class, "random"));

    public static void handleRequest(double random) {
        randomNums.update((int) (random*100));
    }

    public static void main(String[] args) throws InterruptedException {
        reporter.start(3, TimeUnit.SECONDS);
        Random rand = new Random();
        while(true){
            handleRequest(rand.nextDouble());
            Thread.sleep(100);
        }
    }

}

/*
14-2-17 19:39:11 ===============================================================

-- Histograms ------------------------------------------------------------------
com.netease.test.metrics.TestHistograms.random
             count = 30
               min = 1
               max = 97
              mean = 45.93
            stddev = 29.12
            median = 39.50
              75% <= 71.00
              95% <= 95.90
              98% <= 97.00
              99% <= 97.00
            99.9% <= 97.00

14-2-17 19:39:14 ===============================================================

-- Histograms ------------------------------------------------------------------
com.netease.test.metrics.TestHistograms.random
             count = 60
               min = 0
               max = 97
              mean = 41.17
            stddev = 28.60
            median = 34.50
              75% <= 69.75
              95% <= 92.90
              98% <= 96.56
              99% <= 97.00
            99.9% <= 97.00

14-2-17 19:39:17 ===============================================================

-- Histograms ------------------------------------------------------------------
com.netease.test.metrics.TestHistograms.random
             count = 90
               min = 0
               max = 97
              mean = 44.67
            stddev = 28.47
            median = 43.00
              75% <= 71.00
              95% <= 91.90
              98% <= 96.18
              99% <= 97.00
            99.9% <= 97.00
*/

5.       Timers

Timers主要是用来统计某一块代码段的执行时间以及其分布情况，具体是基于Histograms和Meters来实现的。样例代码如下：

package com.netease.test.metrics;

import com.codahale.metrics.ConsoleReporter;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.Timer;

import java.util.Random;
import java.util.concurrent.TimeUnit;

import static com.codahale.metrics.MetricRegistry.name;

/**
 * User: hzwangxx
 * Date: 14-2-17
 * Time: 18:34
 * 测试Timers
 */
public class TestTimers {
    /**
     * 实例化一个registry，最核心的一个模块，相当于一个应用程序的metrics系统的容器，维护一个Map
     */
    private static final MetricRegistry metrics = new MetricRegistry();

    /**
     * 在控制台上打印输出
     */
    private static ConsoleReporter reporter = ConsoleReporter.forRegistry(metrics).build();

    /**
     * 实例化一个Meter
     */
//    private static final Timer requests = metrics.timer(name(TestTimers.class, "request"));
    private static final Timer requests = metrics.timer(name(TestTimers.class, "request"));

    public static void handleRequest(int sleep) {
        Timer.Context context = requests.time();
        try {
            //some operator
            Thread.sleep(sleep);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            context.stop();
        }

    }

    public static void main(String[] args) throws InterruptedException {
        reporter.start(3, TimeUnit.SECONDS);
        Random random = new Random();
        while(true){
            handleRequest(random.nextInt(1000));
        }
    }

}

/*
14-2-18 9:31:54 ================================================================

-- Timers ----------------------------------------------------------------------
com.netease.test.metrics.TestTimers.request
             count = 4
         mean rate = 1.33 calls/second
     1-minute rate = 0.00 calls/second
     5-minute rate = 0.00 calls/second
    15-minute rate = 0.00 calls/second
               min = 483.07 milliseconds
               max = 901.92 milliseconds
              mean = 612.64 milliseconds
            stddev = 196.32 milliseconds
            median = 532.79 milliseconds
              75% <= 818.31 milliseconds
              95% <= 901.92 milliseconds
              98% <= 901.92 milliseconds
              99% <= 901.92 milliseconds
            99.9% <= 901.92 milliseconds

14-2-18 9:31:57 ================================================================

-- Timers ----------------------------------------------------------------------
com.netease.test.metrics.TestTimers.request
             count = 8
         mean rate = 1.33 calls/second
     1-minute rate = 1.40 calls/second
     5-minute rate = 1.40 calls/second
    15-minute rate = 1.40 calls/second
               min = 41.07 milliseconds
               max = 968.19 milliseconds
              mean = 639.50 milliseconds
            stddev = 306.12 milliseconds
            median = 692.77 milliseconds
              75% <= 885.96 milliseconds
              95% <= 968.19 milliseconds
              98% <= 968.19 milliseconds
              99% <= 968.19 milliseconds
            99.9% <= 968.19 milliseconds

14-2-18 9:32:00 ================================================================

-- Timers ----------------------------------------------------------------------
com.netease.test.metrics.TestTimers.request
             count = 15
         mean rate = 1.67 calls/second
     1-minute rate = 1.40 calls/second
     5-minute rate = 1.40 calls/second
    15-minute rate = 1.40 calls/second
               min = 41.07 milliseconds
               max = 968.19 milliseconds
              mean = 591.35 milliseconds
            stddev = 302.96 milliseconds
            median = 650.56 milliseconds
              75% <= 838.07 milliseconds
              95% <= 968.19 milliseconds
              98% <= 968.19 milliseconds
              99% <= 968.19 milliseconds
            99.9% <= 968.19 milliseconds

*/

Health Checks

Metrics提供了一个独立的模块：Health Checks，用于对Application、其子模块或者关联模块的运行是否正常做检测。该模块是独立metrics-core模块的，使用时则导入metrics-healthchecks包。

<dependency>
  <groupId>com.codahale.metrics</groupId>
  <artifactId>metrics-healthchecks</artifactId>
  <version>3.0.1</version>
</dependency>

使用起来和与上述几种类型的Metrics有点类似，但是需要重新实例化一个Metrics容器HealthCheckRegistry，待检测模块继承抽象类HealthCheck并实现check()方法即可，然后将该模块注册到HealthCheckRegistry中，判断的时候通过isHealthy()接口即可。如下示例代码：

package com.netease.test.metrics;

import com.codahale.metrics.health.HealthCheck;
import com.codahale.metrics.health.HealthCheckRegistry;

import java.util.Map;
import java.util.Random;

/**
 * User: hzwangxx
 * Date: 14-2-18
 * Time: 9:57
 */
public class DatabaseHealthCheck extends HealthCheck{
    private final Database database;

    public DatabaseHealthCheck(Database database) {
        this.database = database;
    }

    @Override
    protected Result check() throws Exception {
        if (database.ping()) {
            return Result.healthy();
        }
        return Result.unhealthy("Can't ping database.");
    }

    /**
     * 模拟Database对象
     */
    static class Database {
        /**
         * 模拟database的ping方法
         * @return 随机返回boolean值
         */
        public boolean ping() {
            Random random = new Random();
            return random.nextBoolean();
        }
    }

    public static void main(String[] args) {
//        MetricRegistry metrics = new MetricRegistry();
//        ConsoleReporter reporter = ConsoleReporter.forRegistry(metrics).build();
        HealthCheckRegistry registry = new HealthCheckRegistry();
        registry.register("database1", new DatabaseHealthCheck(new Database()));
        registry.register("database2", new DatabaseHealthCheck(new Database()));
        while (true) {
            for (Map.Entry<String, Result> entry : registry.runHealthChecks().entrySet()) {
                if (entry.getValue().isHealthy()) {
                    System.out.println(entry.getKey() + ": OK");
                } else {
                    System.err.println(entry.getKey() + ": FAIL, error message: " + entry.getValue().getMessage());
                    final Throwable e = entry.getValue().getError();
                    if (e != null) {
                        e.printStackTrace();
                    }
                }
            }
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {

            }
        }
    }
}

/*
console output:
database1: OK
database2: FAIL, error message: Can't ping database.
database1: FAIL, error message: Can't ping database.
database2: OK
database1: OK
database2: FAIL, error message: Can't ping database.
database1: FAIL, error message: Can't ping database.
database2: OK
database1: FAIL, error message: Can't ping database.
database2: FAIL, error message: Can't ping database.
database1: FAIL, error message: Can't ping database.
database2: FAIL, error message: Can't ping database.
database1: OK
database2: OK
database1: OK
database2: FAIL, error message: Can't ping database.
database1: FAIL, error message: Can't ping database.
database2: OK
database1: OK
database2: OK
database1: FAIL, error message: Can't ping database.
database2: OK
database1: OK
database2: OK
database1: OK
database2: OK
database1: OK
database2: FAIL, error message: Can't ping database.
database1: FAIL, error message: Can't ping database.
database2: FAIL, error message: Can't ping database.

 */

其他支持

metrics提供了对Ehcache、Apache HttpClient、JDBI、Jersey、Jetty、Log4J、Logback、JVM等的集成，可以方便地将Metrics输出到Ganglia、Graphite中，供用户图形化展示。

参考资料

http://metrics.codahale.com/

https://github.com/dropwizard/metrics

http://blog.csdn.net/scutshuxue/article/details/8350135

http://blog.synyx.de/2013/09/yammer-metrics-made-easy-part-i/

http://blog.synyx.de/2013/09/yammer-metrics-made-easy-part-ii/

http://wiki.apache.org/hadoop/HADOOP-6728-MetricsV2