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ad service

The ad service provides advertisement based on context keys. If no context keys are provided then it returns random ads.

OpenTelemetry instrumentation

Initialization

In Java, the OpenTelemetry SDK is initialized using a Java agent and environment variables, or Java system command line properties. In this example we use the Honeycomb OpenTelemetry Distro for Java. This is a wrapper to the standard OpenTelemetry Java agent, providing shortcuts to configure for Honeycomb output, and attach a Span processor which will export Baggage members as Span attributes. In this example, we are using an OpenTelmetry Collector in our telemetry pipeline, the following environment variables are used to point ot that configuration:

Other environment variables may be required with other configurations, please refer to the Honeycomb documentation for usage of this agent.

Instrumenting with the @WithSpan annotation

The OpenTelemetry Java SDK provides annotations to facilitate instrumentation. Adding the @WithSpan annotation to any function will wrap that function's execution within a span. You can specify the emitted span name using the @WithSpan("my-name") syntax. If not specified, the class and function name will be used as the span name. The getAds and getRandomAds functions have this annotation.

    // Wrap function in an OpenTelemetry span
    @WithSpan  //results in a span name of AdServiceImpl.getAds
    public void getAds(AdRequest req, StreamObserver<AdResponse> responseObserver) {
        // ...
    }

    // Wrap function in an OpenTelemetry span
    @WithSpan("random-ads")
    private List<Ad> getRandomAds() {
        // ...
    }

Span attributes and events

With the OpenTelemetry Java SDK, you can leverage existing spans that are auto-instrumented, or manually created using Span.current(). This technique is used in the getAds function so attributes and events can be added to the span.

    // Get the current OpenTelemetry span
    Span span = Span.current();

Attributes can be added to the span using Span.setAttribute()

    // Add a span attribute
    span.setAttribute("method", "getAds");
    span.setAttribute("context_keys", req.getContextKeysList().toString());

Span events can be created using Span.addEvent()

    // Add a span event
    span.addEvent(
            "Constructing Ads using context",
            io.opentelemetry.api.common.Attributes.of(
                    AttributeKey.stringKey("Context Keys"), req.getContextKeysList().toString(),
                    AttributeKey.longKey("Context Keys length"), keyCount));