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Client

Introduction

The Jetty client integration has been instrumented with OpenCensus and it provides traces and stats. This integration was added in OpenCensus-Java version 0.19.1.

Imports

To add the Jetty client integration, we’ll perform the following import.

import io.opencensus.contrib.http.jetty.client.OcJettyHttpClient;

Dependency management

Please add these lines to a pom.xml file in your current working directory.

<!-- https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-jetty-client -->
<dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-contrib-http-jetty-client</artifactId>
    <version>0.19.1</version>
</dependency>

<!-- https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-util -->
<dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-contrib-http-util</artifactId>
    <version>0.19.1</version>
</dependency>
// https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-jetty-client
compile group: 'io.opencensus', name: 'opencensus-contrib-http-jetty-client', version: '0.19.1'

// https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-util
compile group: 'io.opencensus', name: 'opencensus-contrib-http-util', version: '0.19.1'
<!-- https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-jetty-client -->
<dependency org="io.opencensus" name="opencensus-contrib-http-jetty-client" rev="0.19.1"/>

<!-- https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-util -->
<dependency org="io.opencensus" name="opencensus-contrib-http-util" rev="0.19.1"/>
# https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-jetty-client
'io.opencensus:opencensus-contrib-http-jetty-client:jar:0.19.1'

# https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-util
'io.opencensus:opencensus-contrib-http-util:jar:0.19.1'

Initializing the client

The client can be initialized simply by

package io.opencensus.tutorials.jetty;

import io.opencensus.contrib.http.jetty.client.OcJettyHttpClient;

public class JettyClient {
  public static void main(String[] args) {
    OcJettyHttpClient httpClient = new OcJettyHttpClient();

    try {
      httpClient.start();
    } catch (Exception e) {
      System.err.println("Failed to start the Jetty Http client " + e);
      return;
    }
  }
}

Enabling observability

Enabling observability takes just a few steps:

Stats

To add stats, we’ll just add an extra step of registering HttpViews like this

import io.opencensus.contrib.http.util.HttpViews;

public class JettyClient {
  private static void registerHttpViews() {
    HttpViews.registerAllClientViews();
  }
}

and after this we’ll ensure that we add any of the Stats exporters

Traces

You don’t need do anything else, except enable Trace exporters

Extracting observability

For the purposes of this demo, we’ll do the following:

End to end example

For assistance running any of the backends for any of the exporters, please refer to:

Exporter URL
Prometheus Prometheus codelab
Zipkin Zipkin codelab

In this example, we’ll be fetching from two different URLs:

URL Purpose
https://opencensus.io/community Existent URL
https://opencensus.io/non-existent Non-existent URL

Source code

package io.opencensus.tutorials.jetty;

import io.opencensus.contrib.http.jetty.client.OcJettyHttpClient;
import io.opencensus.contrib.http.util.HttpViews;
import io.opencensus.exporter.stats.prometheus.PrometheusStatsCollector;
import io.opencensus.exporter.trace.zipkin.ZipkinTraceExporter;
import io.opencensus.trace.Tracing;
import io.opencensus.trace.config.TraceConfig;
import io.opencensus.trace.samplers.Samplers;
import io.prometheus.client.exporter.HTTPServer;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import org.eclipse.jetty.client.HttpRequest;
import org.eclipse.jetty.client.api.ContentResponse;

public class JettyClient {
  public static void main(String[] args) {

    // First things first, enable observability exporters.
    try {
      enableOpenCensusExporters();
    } catch (Exception e) {
      System.err.println("Failed to create the OpenCensus exporters: " + e);
      return;
    }

    OcJettyHttpClient httpClient = new OcJettyHttpClient();

    try {
      httpClient.start();
    } catch (Exception e) {
      System.err.println("Failed to start the Jetty Http client " + e);
      return;
    }

    for (int i = 1; i <= 1000; i++) {
      System.out.println("Iteration: #" + i);

      String[] urls = {"https://opencensus.io/community", "https://opencensus.io/non-existent"};

      for (String url : urls) {
        System.out.println("Fetching URL: " + url);
        // Perform the synchronous request.
        HttpRequest syncRequest = (HttpRequest) httpClient.newRequest(url);
        try {
          ContentResponse response = syncRequest.send();

          byte[] payload = response.getContent();
          String strPayload = new String(response.getContent(), StandardCharsets.UTF_8);
          System.out.println("Payload \n" + strPayload);

          System.out.println("\n\n\nNow sleeping for 5s");
          Thread.sleep(5000);

        } catch (java.lang.InterruptedException e) {
          System.err.println("This thread was interrupted: " + e);
        } catch (java.util.concurrent.TimeoutException e) {
          System.err.println("The request timed out unfortunately: " + e);
        } catch (java.util.concurrent.ExecutionException e) {
          System.err.println("Execution failed: " + e);
        } catch (Exception e) {
          System.err.println("Unhandled exception: " + e);
        }
      }
    }
  }

  private static void enableOpenCensusExporters() throws IOException {
    // Firstly enable stats from the Http client views.
    HttpViews.registerAllClientViews();

    // Register the Prometheus stats collector aka "exporter".
    PrometheusStatsCollector.createAndRegister();
    HTTPServer prometheusServer = new HTTPServer(8889, true);

    // Update the trace sampling rate to 100% aka "AlwaysSample".
    TraceConfig traceConfig = Tracing.getTraceConfig();
    traceConfig.updateActiveTraceParams(
        traceConfig.getActiveTraceParams().toBuilder().setSampler(Samplers.alwaysSample()).build());

    // Enable the Zipkin trace exporter.
    ZipkinTraceExporter.createAndRegister(
        "http://localhost:9411/api/v2/spans", "jetty-client-tutorial");
  }
}
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>io.opencensus.tutorials.jetty</groupId>
    <artifactId>jetty-client-tutorial</artifactId>
    <packaging>jar</packaging>
    <version>0.0.1</version>
    <name>jettyclient</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <opencensus.version>0.19.1</opencensus.version>
        <!-- Change this to the Jetty version that you would like to use -->
        <jetty.version>9.4.12.v20180830</jetty.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>io.opencensus</groupId>
            <artifactId>opencensus-contrib-http-jetty-client</artifactId>
            <version>${opencensus.version}</version>
        </dependency>

        <dependency>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-client</artifactId>
            <version>${jetty.version}</version>
        </dependency>

        <dependency>
            <groupId>io.netty</groupId>
            <artifactId>netty-tcnative-boringssl-static</artifactId>
            <version>2.0.8.Final</version>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>io.opencensus</groupId>
            <artifactId>opencensus-api</artifactId>
            <version>${opencensus.version}</version>
        </dependency>

        <dependency>
            <groupId>io.opencensus</groupId>
            <artifactId>opencensus-impl</artifactId>
            <version>${opencensus.version}</version>
        </dependency>

        <dependency>
            <groupId>io.opencensus</groupId>
            <artifactId>opencensus-exporter-stats-prometheus</artifactId>
            <version>${opencensus.version}</version>
        </dependency>

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

        <dependency>
            <groupId>io.opencensus</groupId>
            <artifactId>opencensus-exporter-trace-zipkin</artifactId>
            <version>${opencensus.version}</version>
        </dependency>
    </dependencies>

    <build>
        <extensions>
            <extension>
                <groupId>kr.motd.maven</groupId>
                <artifactId>os-maven-plugin</artifactId>
                <version>1.5.0.Final</version>
            </extension>
        </extensions>

        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.7.0</version>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>

        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>appassembler-maven-plugin</artifactId>
                <version>1.10</version>
                <configuration>
                    <programs>
                        <program>
                            <id>SQLApp</id>
                            <mainClass>io.opencensus.tutorials.jetty.JettyClient</mainClass>
                        </program>
                    </programs>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Running it

With Zipkin running as per End-to-end example and Prometheus installed, the last step is to turn on Prometheus with this configuration file that we’ll save in prom.yaml

scrape_configs:
  - job_name: 'jetty_tutorial'

    scrape_interval: 5s

    static_configs:
      - targets: ['localhost:8889']

and then run Prometheus like this

prometheus --config.file=prom.yaml

And finally to run the code

mvn install && mvn exec:java -Dexec.mainClass=io.opencensus.tutorials.jetty.JettyClient

Examining your traces

On navigating to the Zipkin UI at http://localhost:9411/zipkin, you should see

All traces

Existent page

Non-Existent page

Examining your stats

On navigating to the Prometheus UI at http://localhost:9090, you should see

All stats

Roundtrip latency

Sent bytes

References

Resource URL
Jetty client JavaDoc org.eclipse.jetty.client
OcJettyClient JavaDoc io.opencensus.contrib.http.jetty.client.OcJettyHttpClient
OcJetty on Maven Central https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-jetty-client
HTTP util on Maven Central https://mvnrepository.com/artifact/io.opencensus/opencensus-contrib-http-util