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Dropwizard

Background

Dropwizard Metrics is a popular solution used by Java developers to capture JVM and application-level metrics from their services. In addition to distributed tracing, OpenCensus also captures application-level metrics from Java services, and interoperability between Dropwizard and OpenCensus has been one of our most asked for Java features.

We have good news: OpenCensus now provides an easy way to export and migrate Dropwizard metrics to OpenCensus, and then on to your backend of choice.

Prerequisites

For assistance setting up Prometheus, Click here for a guided codelab.

You can swap out any other exporter from the list of Java exporters

Adding dependencies

If you’ve got a Maven application, you’ll need to add opencensus-contrib-dropwizard as a dependency.

<dependencies>
    <dependency>
        <groupId>io.opencensus</groupId>
        <artifactId>opencensus-contrib-dropwizard</artifactId>                  
        <version>0.17.0</version>
    </dependency>
</dependencies>

And you can find its latest version [here].

For Gradle add to your dependencies:

compile ‘io.opencensus:opencensus-dropwizard:0.17.0’

Enable an exporter

Add the following code snippet to your <dependencies>...</dependencies> node in pom.xml:

<dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-exporter-stats-prometheus</artifactId>
    <version>0.17.0</version>
</dependency>

<dependency>
    <groupId>io.prometheus</groupId>
    <artifactId>simpleclient_httpserver</artifactId>
    <version>0.4.0</version>
</dependency>

We also need to expose the Prometheus endpoint say on address “localhost:8888” in order for Prometheus to scrape our application. Please add the following to our Java code.

private static void setupOpenCensusAndPrometheusExporter() throws IOException {
  // Register the Prometheus exporter
  PrometheusStatsCollector.createAndRegister();

  // Run the server as a daemon on address "localhost:8888"
  HTTPServer server = new HTTPServer("localhost", 8888, true);
}

End to end example

import java.util.Collections;
import java.io.IOException;
import io.opencensus.exporter.stats.prometheus.PrometheusStatsCollector;
import io.prometheus.client.exporter.HTTPServer;

public class YourClass {
  // Create registry for Dropwizard metrics.
  static final com.codahale.metrics.MetricRegistry
    codahaleRegistry = new com.codahale.metrics.MetricRegistry();

  // Create a Dropwizard counter.
  static final com.codahale.metrics.Counter
     requests = codahaleRegistry.counter("requests");

  public static void main(String[] args) {

    // Increment the requests.
    requests.inc();

    // Hook the Dropwizard registry into the OpenCensus registry
    // via the DropWizardMetrics metric producer.
    io.opencensus.metrics.Metrics.getExportComponent().getMetricProducerManager().add(
          new io.opencensus.contrib.dropwizard.DropWizardMetrics(
            Collections.singletonList(codahaleRegistry)));

    setupOpenCensusAndPrometheusExporter();

    //...Continue with the rest of your application here
  }

  private static void setupOpenCensusAndPrometheusExporter() throws IOException {
    // Register the Prometheus exporter
    PrometheusStatsCollector.createAndRegister();

    // Run the server as a daemon on address "localhost:8888"
    HTTPServer server = new HTTPServer("localhost", 8888, true);
  }
}

Visuals

Here are a few sample charts created out of data exported by OpenCensus using Prometheus exporter.

http://localhost:9090

Go to http://localhost:9090/graph and, start typing “codahale”. Select “codahale_requests_counter”: Prometheus “codahale_requests_counter” Prometheus “codahale_get_requests_duration_size_gauge”

References

Resource URL
Dropwizard Project https://www.dropwizard.io
OpenCensus-Dropwizard on Maven Central https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-dropwizard