如何为单个流程实现dropwizard指标？

Question

Hi I'm new to java and am trying to learn how to use the Dropwizard Metrics library to measure performance of a single process. I've looked at their getting started and have run what they wrote for the MetricsRegistry but don't understand how to combine both the process and the metricsRegistry into one (where it measures the time it takes my process and not the time it takes itself to run).

I could be wording a lot of things wrong but hopefully my question is clear enough. Thanks in advance for any help/clarification I can get! I pasted the code I want to measure below along (pi digits to nth number) with what Dropwizard Metrics gave for their getting started:

package decimals;

import java.util.Scanner;
import java.math.BigDecimal;


public class Decimals {


    public static void main(String[] args) {

        BigDecimal seven = new BigDecimal(7.0);
        Scanner input = new Scanner(System.in);
        System.out.println("to what nth?");
        int i = input.nextInt();
        BigDecimal pi = new BigDecimal(22.0).divide(seven, i, BigDecimal.ROUND_UP);

        if ( i < 0) {
            System.out.println("can't be less than 0");
        } else {
            System.out.println(pi);
        }
    }
}

//dropwizardmetrics:


package com.***.***;
import com.codahale.metrics.*;
import java.util.concurrent.TimeUnit;

public class MetricsRegistry {
    static final MetricRegistry metrics = new MetricRegistry();
    public static void main(String args[]) {
        startReport();
        Meter requests = metrics.meter("requests");
        requests.mark();
        wait5Seconds();
    }

    private static void startReport() {
        ConsoleReporter reporter = ConsoleReporter.forRegistry(metrics)
                .convertRatesTo(TimeUnit.SECONDS)
                .convertDurationsTo(TimeUnit.MILLISECONDS)
                .build();
        reporter.start(2, TimeUnit.SECONDS);
    }

    private static void wait5Seconds() {
        try {
            Thread.sleep(5*1000);
        }
        catch(InterruptedException e) {}
    }



}

Answer 1

Put all your Pi computation logic into a method called computePi(), and try this in your main method:

public static void main(String args[]) {
    startReport();
    Timer timer = metricRegistry.timer("computePi");    
    Timer.Context context = timer.time();
    try {
        computePi();
    } finally {
        context.stop();
    }
}

In your example, you were using a Meter, which does not measure the time it takes to execute (it measures the rate of occurrence and overall count). I changed it be a Timer, which measures time as well. The timer begins when I call timer.time(). Then I execute your computePi() process in a try block. I use a "finally" block to stop the timer no matter what happens inside of computePi(). This is how you get the exact time that it takes to execute your process.