Add simple tests for the tracing pkg

go.mod

@@ -25,6 +25,7 @@ require (
 	go.opentelemetry.io/otel v1.9.1-0.20220810155701-d96e8d2912af
 	go.opentelemetry.io/otel/exporters/zipkin v1.9.0
 	go.opentelemetry.io/otel/sdk v1.9.0
+	go.opentelemetry.io/otel/trace v1.9.0
 	golang.org/x/crypto v0.0.0-20220622213112-05595931fe9d
 	golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4
 )

tracing/tracing.go

@@ -15,12 +15,16 @@ import (
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/zipkin"
 	"go.opentelemetry.io/otel/sdk/trace"
+	apitrace "go.opentelemetry.io/otel/trace"
 )
 
 var (
 	// Enabled reports whether tracing is globally enabled or not.
 	Enabled bool
 
+	// Global Tracer instance.
+	Tracer apitrace.Tracer
+
 	// The active tracing configuration, if Enabled is true.
 	config tracingConfig
 
@@ -37,7 +41,7 @@ type tracingConfig struct {
 // Read the global tracing configuration file. Its location is
 // hardcoded, but it can be overriden using the TRACING_CONFIG
 // environment variable.
-func readTracingConfig() error {
+func readTracingConfig() (*tracingConfig, error) {
 	// Read and decode configuration.
 	cfgPath := globalTracingConfigPath
 	if s := os.Getenv("TRACING_CONFIG"); s != "" {
@@ -45,20 +49,21 @@ func readTracingConfig() error {
 	}
 	data, err := ioutil.ReadFile(cfgPath)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
+	var config tracingConfig
 	if err := json.Unmarshal(data, &config); err != nil {
 		log.Printf("warning: error in tracing configuration: %v, tracing disabled", err)
-		return err
+		return nil, err
 	}
 
 	if config.ReportURL == "" {
 		log.Printf("warning: tracing configuration contains no report_url, tracing disabled")
-		return errors.New("no report_url")
+		return nil, errors.New("no report_url")
 	}
 
-	return nil
+	return &config, nil
 }
 
 // Compute the service name for Zipkin: this is usually the program
@@ -78,24 +83,18 @@ func getServiceName() string {
 // We need to check the configuration as soon as possible, because
 // it's likely that client transports are created before HTTP servers,
 // and we need to wrap them with opencensus at creation time.
-func init() {
-	// Kill switch from environment.
-	if s := os.Getenv("TRACING_ENABLE"); s == "0" {
-		return
-	}
-
-	if err := readTracingConfig(); err != nil {
-		return
-	}
-
-	Enabled = true
-}
-
 func initTracing(endpointAddr string) {
-	if !Enabled {
-		return
-	}
 	initOnce.Do(func() {
+		// Kill switch from environment.
+		if s := os.Getenv("TRACING_ENABLE"); s == "0" {
+			return
+		}
+
+		config, err := readTracingConfig()
+		if err != nil {
+			return
+		}
+
 		ze, err := zipkin.New(config.ReportURL)
 		if err != nil {
 			log.Printf("error creating Zipkin exporter: %v", err)
@@ -123,6 +122,7 @@ func initTracing(endpointAddr string) {
 		)
 
 		otel.SetTracerProvider(tp)
+		Tracer = tp.Tracer(endpointAddr)
 
 		log.Printf("tracing enabled (report_url %s)", config.ReportURL)
 

tracing/tracing_test.go

+package tracing
+
+import (
+	"encoding/json"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+)
+
+func TestTracing(t *testing.T) {
+	h := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+	})
+	httpSrv := httptest.NewServer(h)
+	defer httpSrv.Close()
+
+	tmpf, err := ioutil.TempFile("", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(tmpf.Name())
+	defer tmpf.Close()
+
+	if err := json.NewEncoder(tmpf).Encode(&tracingConfig{
+		ReportURL: httpSrv.URL,
+		Sample:    "1.0",
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	os.Setenv("TRACING_ENABLE", "1")
+	os.Setenv("TRACING_CONFIG", tmpf.Name())
+
+	Init()
+
+	if !Enabled {
+		t.Fatal("tracing not enabled")
+	}
+}