# Vertx Zipkin Tracing

Vert.x integrates with Zipkin thanks to the Zipkin Brave client.

Vert.x uses the ZipKin HTTP sender based using a Vert.x HTTP Client reporting spans to `http://localhost:9411/api/v2/spans` in JSON format.

    Vertx vertx = Vertx.vertx(new VertxOptions()
      .setTracingOptions(
        new ZipkinTracingOptions().setServiceName("A cute service")
      )
    );

The service name is the mandatory Zipkin service name. If you don’t set it, then `a-service` will be used instead.

You can configure the sender to use a specific URL

    Vertx vertx = Vertx.vertx(new VertxOptions()
      .setTracingOptions(
        new ZipkinTracingOptions()
          .setSenderOptions(new HttpSenderOptions().setSenderEndpoint(senderEndpoint))
      )
    );

The default sender uses a single HTTP connection in plain text with compressed bodies.

You can override the configuration of the HTTP sender with custom `HttpClientOptions`.

    Vertx vertx = Vertx.vertx(new VertxOptions()
      .setTracingOptions(
        new ZipkinTracingOptions()
          .setSenderOptions(new HttpSenderOptions()
            .setSenderEndpoint(senderEndpoint)
            .setSsl(true)
            .setKeyCertOptions(sslOptions))
      )
    );

Finally, you can set a custom ZipKin `Tracing` allowing for greater control over the configuration.

    Vertx vertx = Vertx.builder()
      .withTracer(new ZipkinTracerFactory(tracing))
      .build();

## Tracing policy

The tracing policy defines the behavior of a component when tracing is enabled:

- `PROPAGATE`: the component reports a span in the active trace

- `ALWAYS`: the component reports a span in the active trace or creates a new active trace

- `IGNORE`: the component will not be involved in any trace.

The tracing policy is usually configured in the component options.

## HTTP tracing

The Vert.x HTTP server and client reports span around HTTP requests:

- `operationName`: the HTTP method

- tags

- `http.method`: the HTTP method

- `http.url`: the request URL

- `http.status_code`: the HTTP status code

The default HTTP server tracing policy is `ALWAYS`, you can configure the policy with `setTracingPolicy`

    HttpServer server = vertx.createHttpServer(new HttpServerOptions()
      .setTracingPolicy(TracingPolicy.IGNORE)
    );

The default HTTP client tracing policy is `PROPAGATE`, you can configure the policy with `setTracingPolicy`

    HttpClient client = vertx.createHttpClient(new HttpClientOptions()
      .setTracingPolicy(TracingPolicy.IGNORE)
    );

## EventBus tracing

The Vert.x EventBus reports spans around message exchanges.

The default sending policy is `PROPAGATE`, you can configure the policy with `setTracingPolicy`.

    DeliveryOptions options = new DeliveryOptions().setTracingPolicy(TracingPolicy.ALWAYS);
    vertx.eventBus().send("the-address", "foo", options);