SignalFx Tracing Library for Go

The SignalFx Tracing Library for Go helps you automatically instrument Go applications with instrumented library helpers and a tracer to capture and report distributed traces to SignalFx. You can also use the library to manually instrument Go applications with the OpenTracing API.

Requirements and supported software

These are the requirements to use the SignalFx Tracing Library for Go:

• Go 1.12+
• mod or dep dependency management tool

These are the supported libraries you can instrument:

Library	Version
database/sql	Standard Library
gin-gonic/gin	1.5.0
globalsign/mgo	r2018.06.15+
gorilla/mux	1.7+
labstack/echo	4.0+
mongodb/mongo-go-driver	1.0+
net/http	Standard Library

Other libraries are available to instrument, but are in beta and aren't officially supported. You can view all the libraries in the contrib directory.

Configuration values

If the default configuration values don't apply for your environment, override them before running the process you instrument.

Code	Environment Variable	Default Value	Notes
WithServiceName	SIGNALFX_SERVICE_NAME	SignalFx-Tracing	The name of the service.
WithEndpointURL	SIGNALFX_ENDPOINT_URL	http://localhost:9080/v1/trace	The URL to send traces to. Send spans to a Smart Agent, OpenTelemetry Collector, or a SignalFx ingest endpoint.
WithAccessToken	SIGNALFX_ACCESS_TOKEN	none	The access token for your SignalFx organization.
WithGlobalTag	SIGNALFX_SPAN_TAGS	none	Comma-separated list of tags included in every reported span. For example, "key1:val1,key2:val2". Use only string values for tags.
WithRecordedValueMaxLength	SIGNALFX_RECORDED_VALUE_MAX_LENGTH	1200	The maximum number of characters for any Zipkin-encoded tagged or logged value. Behaviour disabled when set to -1.

Instrument a Go application

Follow these steps to instrument target libraries with provided instrumentors.

For more information about how to instrument a Go application, see the examples.

1. Import github.com/signalfx/signalfx-go-tracing to your go mod or dep dependencies.

2. Import the instrumentor for the target library you want to instrument and replace utilities with their traced equivalents.

   Find an instrumentor for each supported target library in the contrib directory. Each instrumentor has an example_test.go file that demonstrates how to instrument a target library. Don't import examples directly in your application.

3. Enable tracing globally with tracing.Start(). This creates a tracer and registers it as the OpenTracing global tracer.

Inject trace context in HTTP requests

Link individual log entries with trace IDs and span IDs associated with corresponding events by passing metadata in HTTP reqeusts.

To inject trace context in HTTP requests, follow these steps:

1. Replace the default HTTP multiplexer:

   import (
     httptrace "github.com/signalfx/signalfx-go-tracing/contrib/net/http"
     "github.com/signalfx/signalfx-go-tracing/ddtrace/tracer" // global tracer
     "github.com/signalfx/signalfx-go-tracing/tracing" // helper
   )

2. Create the new HTTP multiplexer and attach it to your HTTP instance:

   mux := httptrace.NewServeMux()
   mux.HandleFunc("/", handler) // handler to your function
   // add all other routes
   http.ListenAndServe(":8888", mux)

3. Use a helper for the tracer to get the span ID and trace ID from each request:

   func TraceIdFromCtx(ctx context.Context) (result string) {
     if span, ok := tracer.SpanFromContext(ctx); ok {
       result = tracer.TraceIDHex(span.Context())
     }
     return
   }

   It cooperates with the global tracer instance.

Example log injection configuration

This is an example of what injecting span IDs and trace IDs can look like in your environment:

package main

import (
  httptrace "github.com/signalfx/signalfx-go-tracing/contrib/net/http"
  "github.com/signalfx/signalfx-go-tracing/ddtrace/tracer" // global tracer
  "github.com/signalfx/signalfx-go-tracing/tracing" // helper

  "context"
  "fmt"
  "log"
  "net/http"
)

func TraceIdFromCtx(ctx context.Context) (result string) {
  if span, ok := tracer.SpanFromContext(ctx); ok {
    result = tracer.TraceIDHex(span.Context())
  }
  return
}

func handler(w http.ResponseWriter, r *http.Request) {
  ctx := r.Context()
  log.Print("Recevied request for ", r.URL.Path[1:], " ", TraceIdFromCtx(ctx))
}

func main() {
  tracing.Start()
  defer tracing.Stop()
  mux.HandleFunc("/", handler)
  http.ListenAndServe(":8888", mux)
}

API

See the SignalFx Tracing Library for Go API on godoc.

Testing

Test locally using the Go toolset. The grpc.v12 integration will fail because it covers for deprecated methods. This is expected. In the CI environment we vendor this version of the library inside the integration. Under normal circumstances this is not something that we want to do, because users using this integration might be running versions different from the vendored one, creating hard to debug conflicts.

To run integration tests locally, you should set the INTEGRATION environment variable. The dependencies of the integration tests are best run via Docker. To get an idea about the versions and the set-up take a look at our CI config.

The best way to run the entire test suite is using the CircleCI CLI. Simply run circleci build in the repository root. Note that you might have to increase the resources dedicated to Docker to around 4GB.