Setting up Stackdriver Trace for Java

You can enable Stackdriver Trace for Java applications by using OpenCensus. OpenCensus is a set of instrumentation libraries for collecting trace and metric data that work with multiple backends. For the latest details about OpenCensus for Java, along with additional documentation and examples, go to census-instrumentation/opencensus-java.

Installing the library

To collect traces, add OpenCensus tracing and the Stackdriver exporter to your application's Maven or Gradle file:

Maven

View on GitHub Feedback

<dependency>
  <groupId>io.opencensus</groupId>
  <artifactId>opencensus-api</artifactId>
  <version>0.12.2</version>
</dependency>
<dependency>
  <groupId>io.opencensus</groupId>
  <artifactId>opencensus-exporter-trace-stackdriver</artifactId>
  <version>0.12.2</version>
</dependency>
<dependency>
  <groupId>io.opencensus</groupId>
  <artifactId>opencensus-impl</artifactId>
  <version>0.12.2</version>
  <scope>runtime</scope>
</dependency>

Gradle

compile 'io.opencensus:opencensus-api:0.12.2'
compile 'io.opencensus:opencensus-exporter-trace-stackdriver:0.12.2'
runtime 'io.opencensus:opencensus-impl:0.12.2'

Configuring the Stackdriver exporter

In order to export the collected Trace data, use a StackdriverTraceExporter object:

View on GitHub Feedback

public static void createAndRegisterGoogleCloudPlatform(String projectId) throws IOException {
  StackdriverTraceExporter.createAndRegister(
      StackdriverTraceConfiguration.builder()
          .setProjectId(projectId)
          .build());
}

If you are running on Google Cloud infrastructure, then you don't need to call setProjectID and supply your Google Cloud project ID. If you don't set this field, the client library for Java automatically gathers this data from a Google Cloud metadata server.

If you aren't running on Google Cloud infrastructure, then you must supply your Google Cloud project ID to your application.

Regardless of your infrastructure, when you don't explicitly set the Google Cloud project ID, the google-cloud Java library, which is invoked by OpenCensus, automatically determines if the environment variable GOOGLE_CLOUD_PROJECT is set, and if so, the library uses the value of GOOGLE_CLOUD_PROJECT as your Google Cloud project ID. For more information, go to google-cloud-library specifying a project id. To set the environment variable, do the following:

Linux or macOS

export GOOGLE_CLOUD_PROJECT=your-project-id

Windows

set GOOGLE_CLOUD_PROJECT=your-project-id

PowerShell:

$env:GOOGLE_CLOUD_PROJECT="your-project-id"

Add a custom Trace span

While the OpenCensus library contains automatic integrations for several popular web and RPC frameworks, you can also create custom traces:

View on GitHub Feedback

private static final Tracer tracer = Tracing.getTracer();

public static void doWork() {
  // Create a child Span of the current Span.
  try (Scope ss = tracer.spanBuilder("MyChildWorkSpan").startScopedSpan()) {
    doInitialWork();
    tracer.getCurrentSpan().addAnnotation("Finished initial work");
    doFinalWork();
  }
}

private static void doInitialWork() {
  // ...
  tracer.getCurrentSpan().addAnnotation("Doing initial work");
  // ...
}

private static void doFinalWork() {
  // ...
  tracer.getCurrentSpan().addAnnotation("Hello world!");
  // ...
}

Enabling full sampling

Note: Do not use this option in a production environment. Doing so can generate a large volume of trace data and increase your usage bill.

By default, only 1 in 10,000 traces is sampled.

In a developer environment, this sampling rate might be too slow to show you trace data. You can use the alwaysSample option to sample all traces.

To enable full sampling, use the setSampler method and specify the alwaysSample option:

View on GitHub Feedback

public static void doWorkFullSampled() {
  try (
      Scope ss = tracer.spanBuilder("MyChildWorkSpan")
                   .setSampler(Samplers.alwaysSample())
                   .startScopedSpan()) {
    doInitialWork();
    tracer.getCurrentSpan().addAnnotation("Finished initial work");
    doFinalWork();
  }
}

Overriding automatic authentication

With Java, you can override the automatic authentication and project selection. For example, the following sample illustrates how to create an exporter whose credentials expire 60 seconds from creation time:

View on GitHub Feedback

public static void createAndRegisterWithToken(String accessToken) throws IOException {
  Date expirationTime = DateTime.now().plusSeconds(60).toDate();

  GoogleCredentials credentials =
      GoogleCredentials.create(new AccessToken(accessToken, expirationTime));
  StackdriverTraceExporter.createAndRegister(
      StackdriverTraceConfiguration.builder()
          .setProjectId("MyStackdriverProjectId")
          .setCredentials(credentials)
          .build());
}

Configuring your platform

You can use Trace on Google Cloud and when your application runs outside of Google Cloud.

Running on Google Cloud

When your application is running on Google Cloud, your application is automatically authenticated and you don't need to provide authentication credentials. However, you do need to ensure that your Google Cloud platform has the Stackdriver Trace API access scope enabled.

For the following configurations, the default settings for the access scopes have the Stackdriver Trace API enabled:

• App Engine flexible environment

• App Engine standard environment

• Google Kubernetes Engine

• Compute Engine

If you use custom access scopes, then you must ensure that Stackdriver Trace API access scope enabled. For gcloud users, specify access scopes using the --scopes flag and include the trace.append Stackdriver Trace API access scope. For example, to create a GKE cluster with only the Stackdriver Trace API enabled, do the following:

gcloud container clusters create example-cluster-name --scopes=https://www.googleapis.com/auth/trace.append

Running locally and elsewhere

When your application is running outside of Google Cloud, you must provide authentication credentials in the form of a service account to the client library. The service account must contain the Cloud Trace agent role. For instructions, see Creating a service account.

Google Cloud client libraries use Application default credentials (ADC) to find your application's credentials. You provide these credentials by setting the GOOGLE_APPLICATION_CREDENTIALS environment variable:

Linux/macOS

    export GOOGLE_APPLICATION_CREDENTIALS=path-to-your-service-accounts-private-key

Windows

    set GOOGLE_APPLICATION_CREDENTIALS=path-to-your-service-accounts-private-key

PowerShell:

    $env:GOOGLE_APPLICATION_CREDENTIALS="path-to-your-service-accounts-private-key"

Viewing the traces

After deployment, you can view the traces in the Cloud Console Trace Viewer.

Go to the Trace Viewer page

Resources

• OpenCensus
• GitHub: census-instrumentation/opencensus-java
• API Reference Documentation
• Source code
• GitHub issue tracker
• Stack Overflow