Metrics-Java版的指标度量工具之二

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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