[hotrod] Remove most references to OpenTracing (#4585)

## Which problem is this PR solving?
- Part of #3380

Signed-off-by: Yuri Shkuro <github@ysh.us>

examples/hotrod/README.md

@@ -1,12 +1,12 @@
 # Hot R.O.D. - Rides on Demand
 
 This is a demo application that consists of several microservices and illustrates
-the use of the OpenTracing API. It can be run standalone, but requires Jaeger backend
+the use of the OpenTelemetry API & SDK. It can be run standalone, but requires Jaeger backend
 to view the traces. A tutorial / walkthrough is available:
   * as a blog post [Take OpenTracing for a HotROD ride][hotrod-tutorial],
   * as a video [OpenShift Commons Briefing: Distributed Tracing with Jaeger & Prometheus on Kubernetes][hotrod-openshift].
 
-As of Jaeger v1.42.0 this application was upgraded to use OpenTelemetry SDK for traces.
+As of Jaeger v1.42.0 this application was upgraded to use the OpenTelemetry SDK for traces.
 
 ## Features
 
@@ -17,7 +17,7 @@ As of Jaeger v1.42.0 this application was upgraded to use OpenTelemetry SDK for
 * Use baggage propagation to
   * Diagnose inter-request contention (queueing)
   * Attribute time spent in a service
-* Use open source libraries with OpenTracing integration to get vendor-neutral instrumentation for free
+* Use [opentelemetry-go-contrib](https://github.com/open-telemetry/opentelemetry-go-contrib) open source libraries to instrument HTTP and gRPC requests with minimal code changes
 
 ## Running
 

examples/hotrod/pkg/log/factory.go

@@ -40,14 +40,14 @@ func (b Factory) Bg() Logger {
 }
 
 // For returns a context-aware Logger. If the context
-// contains an OpenTracing span, all logging calls are also
+// contains a span, all logging calls are also
 // echo-ed into the span.
 func (b Factory) For(ctx context.Context) Logger {
-	if otelSpan := trace.SpanFromContext(ctx); otelSpan != nil {
-		logger := spanLogger{span: otelSpan, logger: b.logger}
+	if span := trace.SpanFromContext(ctx); span != nil {
+		logger := spanLogger{span: span, logger: b.logger}
 		logger.spanFields = []zapcore.Field{
-			zap.String("trace_id", otelSpan.SpanContext().TraceID().String()),
-			zap.String("span_id", otelSpan.SpanContext().SpanID().String()),
+			zap.String("trace_id", span.SpanContext().TraceID().String()),
+			zap.String("span_id", span.SpanContext().SpanID().String()),
 		}
 		return logger
 	}

examples/hotrod/pkg/tracing/baggage.go

@@ -17,27 +17,10 @@ package tracing
 import (
 	"context"
 
-	"github.com/opentracing/opentracing-go"
 	"go.opentelemetry.io/otel/baggage"
 )
 
 func BaggageItem(ctx context.Context, key string) string {
-	val := opentracingBaggageItem(ctx, key)
-	if val != "" {
-		return val
-	}
-	return otelBaggageItem(ctx, key)
-}
-
-func opentracingBaggageItem(ctx context.Context, key string) string {
-	span := opentracing.SpanFromContext(ctx)
-	if span == nil {
-		return ""
-	}
-	return span.BaggageItem(key)
-}
-
-func otelBaggageItem(ctx context.Context, key string) string {
 	b := baggage.FromContext(ctx)
 	m := b.Member(key)
 	return m.Value()

examples/hotrod/pkg/tracing/init.go

@@ -23,9 +23,7 @@ import (
 	"sync"
 	"time"
 
-	"github.com/opentracing/opentracing-go"
 	"go.opentelemetry.io/otel"
-	otbridge "go.opentelemetry.io/otel/bridge/opentracing"
 	"go.opentelemetry.io/otel/exporters/jaeger"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp"
@@ -46,22 +44,6 @@ var once sync.Once
 
 // InitOTEL initializes OpenTelemetry SDK.
 func InitOTEL(serviceName string, exporterType string, metricsFactory metrics.Factory, logger log.Factory) trace.TracerProvider {
-	_, oteltp := initBOTH(serviceName, exporterType, metricsFactory, logger)
-
-	logger.Bg().Debug("Created OTEL tracer", zap.String("service-name", serviceName))
-	return oteltp
-}
-
-// Init returns OTel-OpenTracing Bridge.
-func Init(serviceName string, exporterType string, metricsFactory metrics.Factory, logger log.Factory) opentracing.Tracer {
-	otTracer, _ := initBOTH(serviceName, exporterType, metricsFactory, logger)
-
-	logger.Bg().Debug("Created OTEL->OT bridge", zap.String("service-name", serviceName))
-	return otTracer
-}
-
-// initBOTH initializes OpenTelemetry SDK and uses OTel-OpenTracing Bridge
-func initBOTH(serviceName string, exporterType string, metricsFactory metrics.Factory, logger log.Factory) (opentracing.Tracer, trace.TracerProvider) {
 	once.Do(func() {
 		otel.SetTextMapPropagator(
 			propagation.NewCompositeTextMapPropagator(
@@ -86,8 +68,8 @@ func initBOTH(serviceName string, exporterType string, metricsFactory metrics.Fa
 			semconv.ServiceNameKey.String(serviceName),
 		)),
 	)
-	otTracer, _ := otbridge.NewTracerPair(tp.Tracer(serviceName))
-	return otTracer, tp
+	logger.Bg().Debug("Created OTEL tracer", zap.String("service-name", serviceName))
+	return tp
 }
 
 // withSecure instructs the client to use HTTPS scheme, instead of hotrod's desired default HTTP

examples/hotrod/services/customer/database.go

@@ -75,12 +75,12 @@ func newDatabase(tracer trace.Tracer, logger log.Factory) *database {
 func (d *database) Get(ctx context.Context, customerID int) (*Customer, error) {
 	d.logger.For(ctx).Info("Loading customer", zap.Int("customer_id", customerID))
 
-	// simulate opentracing instrumentation of an SQL query
 	ctx, span := d.tracer.Start(ctx, "SQL SELECT", trace.WithSpanKind(trace.SpanKindClient))
-	// #nosec
 	span.SetAttributes(
 		semconv.PeerServiceKey.String("mysql"),
-		attribute.Key("sql.query").String(fmt.Sprintf("SELECT * FROM customer WHERE customer_id=%d", customerID)),
+		attribute.
+			Key("sql.query").
+			String(fmt.Sprintf("SELECT * FROM customer WHERE customer_id=%d", customerID)),
 	)
 	defer span.End()