Go Gin OpenTelemetry Integration

This guide demonstrates how to integrate APItoolkit with your Go Chi application for distributed tracing using OpenTelemetry. We'll walk through the code and explain each part of the integration process.

To get started, you'll need to install OpenTelemetry Go packages and some basic configuration.

Prerequisites

Ensure you have already completed the first three steps of the onboarding guide.

Installation

Unlike NodeJs which has Auto Instrumentation, the corresponding Go OpenTelemetry initiative is still a work in progress. As a result, it will be a bit technical but not difficulty. So follow closely.

We will be using this Opensource simple rate limiter as our Starter project.

It has two branches;

• main: Without OpenTelemetry

• withotel_: With OpenTelemetry Integrated

This tutorial will guide you on how to move from are Uninstrumented service to an Instrumented one.

1. Add OpenTelemetry Instrumentation

Kindly run the command below to install the required packages and dependencies.

go get go.opentelemetry.io/otel
go get go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc
go get go.opentelemetry.io/otel/sdk/resource
go get go.opentelemetry.io/otel/sdk/trace

Ensure they are installed correctly

2. Initialize the OpenTelemetry SDK

This is required for any application that exports telemetry data.

Create an otel.go file with OpenTelemetry SDK bootstrapping code for good separation of concern and for ease of continuous improvement. The content of this file would look like this:

package main

import (
	"context"
	"errors"
	"os"
	"time"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/exporters/stdout/stdoutlog"
	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
	"go.opentelemetry.io/otel/log/global"
	"go.opentelemetry.io/otel/propagation"
	sdklog "go.opentelemetry.io/otel/sdk/log"
	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
)

var (
	otlpEndpoint = os.Getenv("OTEL_EXPORTER_OTLP_ENDPOINT")
)

// setupOTelSDK bootstraps the OpenTelemetry pipeline.
func setupOTelSDK(ctx context.Context) (shutdown func(context.Context) error, err error) {
	var shutdownFuncs []func(context.Context) error

	// Set up propagator
	prop := propagation.NewCompositeTextMapPropagator(
		propagation.TraceContext{},
		propagation.Baggage{},
	)
	otel.SetTextMapPropagator(prop)

	// Set up trace provider
	traceExporter, err := otlptracegrpc.New(ctx,
		otlptracegrpc.WithEndpoint(otlpEndpoint),
		otlptracegrpc.WithInsecure(),
	)
	if err != nil {
		return nil, err
	}
	tracerProvider := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(traceExporter, sdktrace.WithBatchTimeout(5*time.Second)),
	)
	shutdownFuncs = append(shutdownFuncs, tracerProvider.Shutdown)
	otel.SetTracerProvider(tracerProvider)

	// Set up meter provider
	metricExporter, err := stdoutmetric.New()
	if err != nil {
		return nil, err
	}
	meterProvider := sdkmetric.NewMeterProvider(
		sdkmetric.WithReader(sdkmetric.NewPeriodicReader(metricExporter, sdkmetric.WithInterval(3*time.Second))),
	)
	shutdownFuncs = append(shutdownFuncs, meterProvider.Shutdown)
	otel.SetMeterProvider(meterProvider)

	// Set up logger provider
	logExporter, err := stdoutlog.New()
	if err != nil {
		return nil, err
	}
	loggerProvider := sdklog.NewLoggerProvider(
		sdklog.WithProcessor(sdklog.NewBatchProcessor(logExporter)),
	)
	shutdownFuncs = append(shutdownFuncs, loggerProvider.Shutdown)
	global.SetLoggerProvider(loggerProvider)

	// Return shutdown function
	return func(ctx context.Context) error {
		var err error
		for _, fn := range shutdownFuncs {
			err = errors.Join(err, fn(ctx))
		}
		return err
	}, nil
}

What's happening above:

• This function sets up the OpenTelemetry tracer provider with an OTLP gRPC exporter.

• It configures the service name and ensures all spans are sampled.

3. Instrument your application

Now that we have the OpenTelemetry SDK initializer set up, we can instrument our HTTP server.

Modify your main.go file to include code that initializes OpenTelemetry SDK and instruments the HTTP server using the otelhttp instrumentation library:

package main

import (
	"context"
	"flag"
	"log"

	"github.com/fatih/color"
	"github.com/gin-gonic/gin"
	"go.opentelemetry.io/contrib/instrumentation/github.com/gin-gonic/gin/otelgin"
	"go.uber.org/ratelimit"
)

var (
	limit ratelimit.Limiter
	rps   = flag.Int("rps", 100, "request per second")
)

func init() {
	log.SetFlags(0)
	log.SetPrefix("[GIN] ")
	log.SetOutput(gin.DefaultWriter)
}

func ginRun(rps int) {
	limit = ratelimit.New(rps)
	app := gin.Default()
	app.Use(otelgin.Middleware("gin test project"))
	app.Use(leakBucket())
	app.GET("/rate", handleRate)

	log.Printf(color.CyanString("Current Rate Limit: %v requests/s", rps))
	app.Run(":8081")
}

func main() {
	flag.Parse()

	// Set up OTel
	ctx := context.Background()
	shutdown, err := setupOTelSDK(ctx)
	if err != nil {
		log.Fatalf("Error setting up OTel SDK: %v", err)
	}
	defer func() {
		if err := shutdown(ctx); err != nil {
			log.Fatalf("Error shutting down OTel SDK: %v", err)
		}
	}()

	ginRun(*rps)
}

4. Add Custom Instrumentation

Instrumentation libraries capture telemetry at the edges of your systems, such as inbound and outbound HTTP requests, but they don’t capture what’s going on in your application. For that you’ll need to write some custom manual instrumentation.

Go to the rate_limiter.go and modify the handleRate function to include custom instrumentation using OpenTelemetry API:

package main

import (
	"fmt"
	"log"
	"time"

	"github.com/fatih/color"
	"github.com/gin-gonic/gin"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
)

func leakBucket() gin.HandlerFunc {
	prev := time.Now()
	return func(ctx *gin.Context) {
		now := limit.Take()
		log.Print(color.CyanString("%v", now.Sub(prev)))
		prev = now
	}
}

func handleRate(ctx *gin.Context) {
	// Initialize OpenTelemetry tracer
	tracer := otel.Tracer("rate-limiter-service")
	_, span := tracer.Start(ctx, "rate-limiting")
	defer span.End()

	// Extract request data
	method := ctx.Request.Method
	scheme := "http"
	statusCode := 200
	host := ctx.Request.Host
	port := ctx.Request.URL.Port()
	if port == "" {
		port = "8081"
	}
	startTime := time.Now()

	// Set span status
	span.SetStatus(codes.Ok, "")

	// Add semantic conventions for HTTP request attributes
	span.SetAttributes(
		semconv.HTTPMethodKey.String(method),
		semconv.HTTPSchemeKey.String(scheme),
		semconv.HTTPStatusCodeKey.Int(statusCode),
		semconv.HTTPTargetKey.String(ctx.Request.URL.Path),
		semconv.HTTPURLKey.String(ctx.Request.URL.String()),
		semconv.HTTPHostKey.String(host),
		semconv.NetHostPortKey.String(port),
		semconv.HTTPUserAgentKey.String(ctx.Request.UserAgent()),
		semconv.HTTPRequestContentLengthKey.Int64(ctx.Request.ContentLength),
		semconv.NetPeerIPKey.String(ctx.ClientIP()),
	)

	// Custom attributes for OpenTelemetry span
	span.SetAttributes(
		attribute.String("created_at", startTime.Format(time.RFC3339Nano)),
		attribute.Float64("duration_ns", float64(time.Since(startTime).Nanoseconds())),
		attribute.String("referer", ctx.Request.Referer()),
		attribute.String("request_type", "Incoming"),
		attribute.String("sdk_type", "go-gin"),
		attribute.String("service_version", "1.0.0"), // Add your service version here
		attribute.StringSlice("tags", []string{}),
	)

	// Additional request-specific attributes (path params, query params, headers, body)
	span.SetAttributes(
		attribute.String("query_params", ctx.Request.URL.RawQuery),
		attribute.String("request_body", "{}"), // Assuming empty body for demonstration
		attribute.String("request_headers", fmt.Sprintf("%v", ctx.Request.Header)),
		attribute.String("response_body", "{}"),
		attribute.String("response_headers", "{}"),
	)

	// Respond with JSON
	ctx.JSON(statusCode, "rate limiting test")
}

Set Your Environment Variables

Before running your application, set the following environment variables:

export OTEL_TRACES_EXPORTER="otlp"
export OTEL_EXPORTER_OTLP_ENDPOINT="otelcol.apitoolkit.io:4317"
export OTEL_NODE_RESOURCE_DETECTORS="env,host,os"
export OTEL_SERVICE_NAME="my go gin project test"
export OTEL_RESOURCE_ATTRIBUTES=at-project-key="z6BJfZVEOSozztMfhqZsGTpG9DiXT9Weurvk1bpe9mwF8orB"
export OTEL_EXPORTER_OTLP_PROTOCOL="grpc"
export OTEL_PROPAGATORS="baggage,tracecontext"

Quick overview of the configuration parameters

5. Run the application to Ensure Everything works

Build and run the application with the following command:

go mod tidy
go run .

The server will start on port 8081. You can test it by sending a request:

curl http://localhost:8081/rate

This should return: "rate limiting test"

With this setup, your application will send traces to APItoolkit for visualization and analysis.