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:

<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>

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:

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

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

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

Regardless of your infrastructure, when you don't explicitly set the GCP 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 GCP project ID. For more information, go to google-cloud-library specifying a project id. To set the environment variable, do the following:

export GOOGLE_CLOUD_PROJECT=your-project-id

set GOOGLE_CLOUD_PROJECT=your-project-id

$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:

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

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:

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:

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 GCP and when your application runs outside of GCP.

Running on GCP

When your application is running on GCP, your application is automatically authenticated and you don't need to provide authentication credentials. However, you do need to ensure that your GCP 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 GCP, 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.

GCP 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:

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

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

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

Viewing the traces

After deployment, you can view the traces in the GCP 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