GRPC-Java OpenTracing

Installation

This package is available on Maven Central and can be added to your project as follows:

Maven

<dependencies>
    <dependency>
        <groupId>io.opentracing.contrib</groupId>
        <artifactId>grpc-opentracing</artifactId>
        <version>0.2.0</version>
    </dependency>
</dependencies>

Gradle

compile 'io.opentracing.contrib:grpc-opentracing:0.2.0'

Quickstart

If you want to add basic tracing to your clients and servers, you can do so in a few short and simple steps, as shown below. (These code snippets use the grpc example's GreeterGrpc, generated by protocol buffers.)

Servers

• Instantiate a tracer
• Create a ServerTracingInterceptor
• Intercept a service
• (Optional) Access the current span

import io.opentracing.Tracer;

public class YourServer {

    private int port;
    private Server server;
    // Any io.opentracing.Tracer implementation will do here. For instance,
    //   https://github.com/uber/jaeger-client-java/blob/master/jaeger-core/src/main/java/com/uber/jaeger/Tracer.java
    // generates Zipkin-compatible data.
    private final Tracer tracer;

    private void start() throws IOException {
        ServerTracingInterceptor tracingInterceptor = new ServerTracingInterceptor(this.tracer);

        server = ServerBuilder.forPort(port)
            .addService(tracingInterceptor.intercept(someServiceDef))
            .build()
            .start();
    }
}

Clients

• Instantiate a tracer
• Create a ClientTracingInterceptor
• Intercept the client channel

import io.opentracing.Tracer;

public class YourClient {

    private final ManagedChannel channel;
    private final GreeterGrpc.GreeterBlockingStub blockingStub;
    // Any io.opentracing.Tracer implementation will do here. For instance,
    //   https://github.com/uber/jaeger-client-java/blob/master/jaeger-core/src/main/java/com/uber/jaeger/Tracer.java
    // generates Zipkin-compatible data.
    private final Tracer tracer;

    public YourClient(String host, int port) {

        channel = ManagedChannelBuilder.forAddress(host, port)
            .usePlaintext(true)
            .build();

        ClientTracingInterceptor tracingInterceptor = new ClientTracingInterceptor(this.tracer)

        blockingStub = GreeterGrpc.newBlockingStub(tracingInterceptor.intercept(channel));
    }
}

There's an example of a simple traced client (TracedClient) and server (TracedService) in src/test.

Server Tracing

A ServerTracingInterceptor uses default settings, which you can override by creating it using a ServerTracingInterceptor.Builder.

• withOperationName(OperationNameConstructor constructor): Define how the operation name is constructed for all spans created for the intercepted service. Default sets the operation name as the name of the RPC method. More details in the Operation Name section.
• withStreaming(): Logs to the server span whenever a message is received. Note: This package supports streaming but has not been rigorously tested. If you come across any issues, please let us know.
• withVerbosity(): Logs to the server span additional events, such as message received, half close (client finished sending messages), and call complete. Default only logs if a call is cancelled.
• withTracedAttributes(ServerRequestAttribute... attrs): Sets tags on the server span in case you want to track information about the RPC call. See ServerRequestAttribute.java for a list of traceable request attributes.

Example:

ServerTracingInterceptor tracingInterceptor = new ServerTracingInterceptor
    .Builder(tracer)
    .withStreaming()
    .withVerbosity()
    .withOperationName(new OperationNameConstructor() {
        @Override
        public <ReqT, RespT> String constructOperationName(MethodDescriptor<ReqT, RespT> method) {
            // construct some operation name from the method descriptor
        }
    })
    .withTracedAttributes(ServerRequestAttribute.HEADERS,
        ServerRequestAttribute.METHOD_TYPE)
    .build();

Client Tracing

A ClientTracingInterceptor also has default settings, which you can override by creating it using a ClientTracingInterceptor.Builder.

• withOperationName(String operationName): Define how the operation name is constructed for all spans created for this intercepted client. Default is the name of the RPC method. More details in the Operation Name section.
• withActiveSpanSource(ActiveSpanSource activeSpanSource): Define how to extract the current active span, if any. This is needed if you want your client to continue a trace instead of starting a new one. More details in the Active Span Source section.
• withStreaming(): Logs to the client span whenever a message is sent or a response is received. Note: This package supports streaming but has not been rigorously tested. If you come across any issues, please let us know.
• withVerbosity(): Logs to the client span additional events, such as call started, message sent, half close (client finished sending messages), response received, and call complete. Default only logs if a call is cancelled.
• withTracedAttributes(ClientRequestAttribute... attrs): Sets tags on the client span in case you want to track information about the RPC call. See ClientRequestAttribute.java for a list of traceable request attributes.

Example:

import io.opentracing.Span;

ClientTracingInterceptor tracingInterceptor = new ClientTracingInterceptor
    .Builder(tracer)
    .withStreaming()
    .withVerbosity()
    .withOperationName(new OperationNameConstructor() {
        @Override
        public <ReqT, RespT> String constructOperationName(MethodDescriptor<ReqT, RespT> method) {
            // construct some operation name from the method descriptor
        }
    })
    .withActiveSpanSource(new ActiveSpanSource() {
        @Override
        public Span getActiveSpan() {
            // implement how to get the current active span, for example:
            return OpenTracingContextKey.activeSpan();
        }
    })
    .withTracingAttributes(ClientRequestAttribute.ALL_CALL_OPTIONS,
        ClientRequestAttribute.HEADERS)
    .build();

Current Span Context

In your server request handler, you can access the current active span for that request by calling

Span span = OpenTracingContextKey.activeSpan();

This is useful if you want to manually set tags on the span, log important events, or create a new child span for internal units of work. You can also use this key to wrap these internal units of work with a new context that has a user-defined active span.

For example:

Tracer tracer = ...;

// some unit of internal work that you want to trace
Runnable internalWork = someInternalWork

// a wrapper that traces the work of the runnable
class TracedRunnable implements Runnable {
    Runnable work;
    Tracer tracer;

    TracedRunnable(Runnable work, Tracer tracer) {
        this.work = work;
        this.tracer = tracer;
    }

    public void run() {

        // create a child span for the current active span
        Span span = tracer
            .buildSpan("internal-work")
            .asChildOf(OpenTracingContextKey.activeSpan())
            .start();

        // create a new context with the child span as the active span
        Context contextWithNewSpan = Context.current()
            .withValue(OpenTracingContextKey.get(), span);

        // wrap the original work and run it
        Runnable tracedWork = contextWithNewSpan.wrap(this.work);
        tracedWork.run();

        // make sure to finish any manually created spans!
        span.finish();
    }
}

Runnable tracedInternalWork = new TracedRunnable(internalWork, tracer);
tracedInternalWork.run();

Operation Names

The default operation name for any span is the RPC method name (io.grpc.MethodDescriptor.getFullMethodName()). However, you may want to add your own prefixes, alter the name, or define a new name. For examples of good operation names, check out the OpenTracing semantics.

To alter the operation name, you need to add an implementation of the interface OperationNameConstructor to the ClientTracingInterceptor.Builder or ServerTracingInterceptor.Builder. For example, if you want to add a prefix to the default operation name of your ClientInterceptor, your code would look like this:

ClientTracingInterceptor interceptor = ClientTracingInterceptor.Builder ...
    .withOperationName(new OperationNameConstructor() {
        @Override
        public <ReqT, RespT> String constructOperationName(MethodDescriptor<ReqT, RespT> method) {
            return "your-prefix" + method.getFullMethodName();
        }
    })
    .with....
    .build()

Active Span Sources

If you want your client to continue a trace rather than starting a new one, then you can tell your ClientTracingInterceptor how to extract the current active span by building it with your own implementation of the interface ActiveSpanSource. This interface has one method, getActiveSpan, in which you will define how to access the current active span.

For example, if you're creating the client in an environment that has the active span stored in a global dictionary-style context under OPENTRACING_SPAN_KEY, then you could configure your Interceptor as follows:

import io.opentracing.Span;

ClientTracingInterceptor interceptor = new ClientTracingInterceptor
    .Builder(tracer)
    ...
    .withActiveSpanSource(new ActiveSpanSource() {
        @Override
        public Span getActiveSpan() {
            return Context.get(OPENTRACING_SPAN_KEY);
        }
    })
    ...
    .build();

We also provide two built-in implementations:

• ActiveSpanSource.GRPC_CONTEXT uses the current io.grpc.Context and returns the active span for OpenTracingContextKey. This is the default active span source.
• ActiveSpanSource.NONE always returns null as the active span, which means the client will always start a new trace

Integrating with Other Interceptors

Although we provide ServerTracingInterceptor.intercept(service) and ClientTracingInterceptor.intercept(channel) methods, you don't want to use these if you're chaining multiple interceptors. Instead, use the following code (preferably putting the tracing interceptor at the top of the interceptor stack so that it traces the entire request lifecycle, including other interceptors):

Servers

server = ServerBuilder.forPort(port)
    .addService(ServerInterceptors.intercept(service, someInterceptor,
        someOtherInterceptor, serverTracingInterceptor))
    .build()
    .start();

Clients

blockingStub = GreeterGrpc.newBlockingStub(ClientInterceptors.intercept(channel,
    someInterceptor, someOtherInterceptor, clientTracingInterceptor));

Releasing new versions

Create a gradle.properties in this directory. It should look approximately like this:

sonatypeUsername=bensigelman
sonatypePassword=<your OSSRH sonatype password>
signing.keyId=<`gpg --list-keys` output, minus the prefix like "2048R/">
signing.password=<your gpg password>
signing.secretKeyRingFile=/Your/Homedir/.gnupg/secring.gpg

Then run:

$ gradle uploadArchives closeAndPromoteRepository