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Observability

Connect stays close to net/http, which means any logging, tracing, or metrics that work with an http.Handler or http.Client will also work with Connect. In particular, the otelhttp OpenTelemetry package and the ochttp OpenCensus package both integrate seamlessly with Connect servers and clients.

For more detailed, RPC-focused metrics, use the otelconnect package. otelconnect works with your OpenTelemetry metrics and tracing setup to capture information such as:

  • rpc.system: Was this call gRPC, gRPC-Web, or Connect?
  • rpc.service and rpc.method: What service and method was called?
  • responses_per_rpc: How many messages were written to streaming responses?
  • error_code/status_code: What specific gRPC or Connect error was returned?

OpenTelemetry can be quite complex, so this guide assumes that readers are familiar with:

Enabling OpenTelemetry for Connect​

Once you have OpenTelemetry set up in your application, enabling OpenTelemetry in a Connect project is as simple as adding the otelconnect.NewInterceptor option on Connect handler and client constructors. If you do not have OpenTelemetry in your application, you can refer to the OpenTelemetry Go getting started guide.

import "connectrpc.com/otelconnect"

path, handler := greetv1connect.NewGreetServiceHandler(
    greeter,
    connect.WithInterceptors(
        otelconnect.NewInterceptor(),
    ),
)

client := greetv1connect.NewGreetServiceClient(
    http.DefaultClient,
    "http://localhost:8080",
    connect.WithInterceptors(
        otelconnect.NewInterceptor(),
    ),
)

By default, this will use:

  • TextMapPropagator from otel.GetTextMapPropagator()
  • MeterProvider from global.MeterProvider()
  • TracerProvider from otel.GetTracerProvider()

Using custom MeterProvider, TraceProvider and TextMapPropagators​

When running multiple applications in a single binary, or if different sections of code should use different exporters, pass the correct exporters to otelconnect.NewInterceptor explicitly:

// newInterceptor instruments Connect clients and handlers using custom OpenTelemetry metrics, tracing, and propagation.
func newInterceptor(tp trace.TracerProvider, mp metric.MeterProvider, p propagation.TextMapPropagator) (connect.Interceptor, error) {
    return otelconnect.NewInterceptor(
        otelconnect.WithTracerProvider(tp),
        otelconnect.WithMeterProvider(mp),
        otelconnect.WithPropagator(p),
    )
}

Configuration for internal microservices​

By default, otelconnect-instrumented servers are conservative and behave as though they're internet-facing. They don't trust any tracing information sent by the client, and will create new trace spans for each request. The new spans are linked to the remote span for reference (using OpenTelemetry's trace.Link), but tracing UIs will display the request as a new top-level transaction.

If your server is deployed as an internal microservice, configure otelconnect to trust the client's tracing information using otelconnect.WithTrustRemote. With this option, servers will create child spans for each request.

Reducing metrics and tracing cardinality​

By default, the OpenTelemetry RPC conventions produce high-cardinality server-side metric and tracing output. In particular, servers tag all metrics and trace data with the server's IP address and the remote port number. To drop these attributes, use otelconnect.WithoutServerPeerAttributes. For more customizable attribute filtering, use otelconnect.WithFilter.