Testing Jaeger service maps

main.go

package main

import (
	"context"
	"fmt"
	"io"
	"log"
	"net/http"
	"time"

	"github.com/opentracing/opentracing-go"
	"github.com/opentracing/opentracing-go/ext"
	"github.com/uber/jaeger-client-go/config"
	"golang.org/x/sync/errgroup"
)

const (
	addrServiceA = "localhost:1234"
	addrServiceB = "localhost:4321"
)

func newTracer(name string) (opentracing.Tracer, io.Closer, error) {
	cfg, err := config.FromEnv()
	if err != nil {
		return nil, nil, err
	}
	cfg.ServiceName = name
	cfg.Sampler.Type = "const"
	cfg.Sampler.Param = 1
	return cfg.NewTracer()
}

func runServiceA(ctx context.Context) error {
	tracer, closer, err := newTracer("jaeger-service-a")
	if err != nil {
		return err
	}
	defer closer.Close()

	return http.ListenAndServe(addrServiceA, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		spanCtx, _ := tracer.Extract(opentracing.HTTPHeaders, opentracing.HTTPHeadersCarrier(r.Header))
		serverSpan := tracer.StartSpan("server", ext.RPCServerOption(spanCtx))
		defer serverSpan.Finish()

		clientSpan := tracer.StartSpan("client", opentracing.ChildOf(serverSpan.Context()))
		defer clientSpan.Finish()
		ext.SpanKindRPCClient.Set(clientSpan)

		req, _ := http.NewRequest("GET", fmt.Sprintf("http://%s/", addrServiceB), nil)
		ext.HTTPUrl.Set(clientSpan, req.URL.String())
		ext.HTTPMethod.Set(clientSpan, req.Method)

		// Inject the client span context into the headers
		tracer.Inject(clientSpan.Context(), opentracing.HTTPHeaders, opentracing.HTTPHeadersCarrier(req.Header))
		resp, err := http.DefaultClient.Do(req)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		defer resp.Body.Close()
		ext.HTTPStatusCode.Set(clientSpan, uint16(resp.StatusCode))

		w.WriteHeader(resp.StatusCode)
		io.Copy(w, resp.Body)
	}))
}

func runServiceB(ctx context.Context) error {
	tracer, closer, err := newTracer("jaeger-service-b")
	if err != nil {
		return err
	}
	defer closer.Close()

	return http.ListenAndServe(addrServiceB, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		spanCtx, _ := tracer.Extract(opentracing.HTTPHeaders, opentracing.HTTPHeadersCarrier(r.Header))
		serverSpan := tracer.StartSpan("server", ext.RPCServerOption(spanCtx))
		defer serverSpan.Finish()

		dbSpan := tracer.StartSpan("querying database", opentracing.ChildOf(serverSpan.Context()))
		ext.DBStatement.Set(dbSpan, "SELECT * FROM table")
		ext.DBType.Set(dbSpan, "sql")
		ext.PeerHostname.Set(dbSpan, "mysql-host")
		ext.PeerPort.Set(dbSpan, 3306)
		ext.PeerService.Set(dbSpan, "mysql")
		time.Sleep(time.Millisecond)
		dbSpan.Finish()

		clientSpan := tracer.StartSpan("client", opentracing.ChildOf(serverSpan.Context()))
		defer clientSpan.Finish()
		ext.SpanKindRPCClient.Set(clientSpan)

		req, _ := http.NewRequest("GET", "https://testing.invalid/", nil)
		ext.HTTPUrl.Set(clientSpan, req.URL.String())
		ext.HTTPMethod.Set(clientSpan, req.Method)
		resp, err := http.DefaultClient.Do(req)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		defer resp.Body.Close()
		ext.HTTPStatusCode.Set(clientSpan, uint16(resp.StatusCode))
	}))
}

func main() {
	g, ctx := errgroup.WithContext(context.Background())
	g.Go(func() error { return runServiceA(ctx) })
	g.Go(func() error { return runServiceB(ctx) })
	if err := g.Wait(); err != nil {
		log.Fatal(err)
	}
}