Java Open Standards

Java Open Standards

OpenTracing

Datadog integrates seamlessly with the OpenTracing API.

Setup

For Maven, add this to pom.xml:

<!-- OpenTracing API -->
<dependency>
    <groupId>io.opentracing</groupId>
    <artifactId>opentracing-api</artifactId>
    <version>0.32.0</version>
</dependency>

<dependency>
    <groupId>io.opentracing</groupId>
    <artifactId>opentracing-util</artifactId>
    <version>0.32.0</version>
</dependency>

<!-- Datadog API -->
<dependency>
    <groupId>com.datadoghq</groupId>
    <artifactId>dd-trace-api</artifactId>
    <version>${dd-trace-java.version}</version>
</dependency>

<!-- Datadog OpenTracing bridge (only needed if you do not use dd-java-agent for autoinstrumentation) -->
<dependency>
    <groupId>com.datadoghq</groupId>
    <artifactId>dd-trace-ot</artifactId>
    <version>${dd-trace-java.version}</version>
</dependency>

For Gradle, add:

compile group: 'io.opentracing', name: 'opentracing-api', version: "0.32.0"
compile group: 'io.opentracing', name: 'opentracing-util', version: "0.32.0"
compile group: 'com.datadoghq', name: 'dd-trace-api', version: "${dd-trace-java.version}"
// Datadog OpenTracing bridge (only needed if you do not use dd-java-agent for autoinstrumentation)
compile group: 'com.datadoghq', name: 'dd-trace-ot', version: "${dd-trace-java.version}"

Configure your application using environment variables or system properties as discussed in the configuration section.

If you’re not using autoinstrumentation, you must register a configured tracer with GlobalTracer. For this, call GlobalTracer.register(DDTracer.builder().build()) early on in your application startup (for example, main method).

import datadog.opentracing.DDTracer;
import io.opentracing.Tracer;
import io.opentracing.util.GlobalTracer;

public class Application {
    public static void main(String[] args) {
        DDTracer tracer = DDTracer.builder().build();
        GlobalTracer.register(tracer);
        // register the same tracer with the Datadog API
        datadog.trace.api.GlobalTracer.registerIfAbsent(tracer);
    }
}

Aside from environment variables and system properties, there are additional configuration options as part of the DDTracer.Builder interface. Consult the Javadoc for a full listing.

Note: Never add dd-java-agent to your classpath. Doing so can cause unexpected behavior.

Asynchronous traces

An asynchronous trace is when a span is started in one thread and finished in another. To instrument this behavior, a new scope must be used in each thread the span is active.

// Step 1: start the Scope/Span on the work submission thread
final Tracer tracer = GlobalTracer.get();
final Span span = tracer.buildSpan("ServicehandlerSpan").start();

try (final Scope scope = tracer.activateSpan(span)) {
    // submission thread impl...

    submitAsyncTask(new Runnable() {
        @Override
        public void run() {
            // Step 2: reactivate the Span in the worker thread
            try (final Scope scope = tracer.activateSpan(span)) {
              // worker thread impl
            } finally {
              // Step 3: Finish Span when work is complete
              span.finish();
            }
       }
    });
}

Inject and extract context for distributed tracing

Create a distributed trace using manual instrumentation with OpenTracing:

// Step 1: Inject the Datadog headers in the client code
Span span = tracer.buildSpan("httpClientSpan").start();
try (Scope scope = tracer.activate(span)) {
    HttpRequest request = /* your code here */;

    tracer.inject(span.context(),
                  Format.Builtin.HTTP_HEADERS,
                  new MyHttpHeadersInjectAdapter(request));

    // http request impl...
} finally {
    span.finish();
}

public static class MyHttpHeadersInjectAdapter implements TextMap {
    private final HttpRequest httpRequest;

    public HttpHeadersInjectAdapter(final HttpRequest httpRequest) {
        this.httpRequest = httpRequest;
    }

    @Override
    public void put(final String key, final String value) {
        httpRequest.addHeader(key, value);
    }

    @Override
    public Iterator<Map.Entry<String, String>> iterator() {
        throw new UnsupportedOperationException("This class should be used only with tracer#inject()");
    }
}

// Step 2: Extract the Datadog headers in the server code
HttpRequest request = /* your code here */;

final SpanContext extractedContext =
  GlobalTracer.get().extract(Format.Builtin.HTTP_HEADERS,
                             new MyHttpRequestExtractAdapter(request));

// is a child of http client span in step 1
Span span = tracer.buildSpan("httpServerSpan").asChildOf(extractedContext).start();
try (Scope scope = tracer.activateSpan(span)) {
    // http server impl...
} finally {
    span.finish();
}

public class MyHttpRequestExtractAdapter implements TextMap {
    private final HttpRequest request;

    public HttpRequestExtractAdapter(final HttpRequest request) {
        this.request = request;
    }

    @Override
    public Iterator<Map.Entry<String, String>> iterator() {
        return request.headers().iterator();
    }

    @Override
    public void put(final String key, final String value) {
        throw new UnsupportedOperationException("This class should be used only with Tracer.extract()!");
    }
}

Notice the above examples only use the OpenTracing classes. Check the OpenTracing API for more details and information.