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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package main
import (
"context"
"fmt"
"log"
"net/http"
"time"
"go.opentelemetry.io/contrib/examples/passthrough/handler"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
"go.opentelemetry.io/otel/propagation"
sdktrace "go.opentelemetry.io/otel/sdk/trace"
"go.opentelemetry.io/otel/trace"
)
const name = "go.opentelemetry.io/contrib/examples/passthrough"
func main() {
ctx := context.Background()
initPassthroughGlobals()
tp, err := nonGlobalTracer()
if err != nil {
log.Fatal(err)
}
defer func() { _ = tp.Shutdown(ctx) }()
// make an initial http request
r, err := http.NewRequest("", "", nil)
if err != nil {
panic(err)
}
// This is roughly what an instrumented http client does.
log.Println("The \"make outer request\" span should be recorded, because it is recorded with a Tracer from the SDK TracerProvider")
var span trace.Span
tracer := tp.Tracer(name)
ctx, span = tracer.Start(ctx, "make outer request")
defer span.End()
r = r.WithContext(ctx)
otel.GetTextMapPropagator().Inject(ctx, propagation.HeaderCarrier(r.Header))
backendFunc := func(r *http.Request) {
// This is roughly what an instrumented http server does.
ctx := r.Context()
tp := trace.SpanFromContext(ctx).TracerProvider()
tracer := tp.Tracer(name)
ctx = otel.GetTextMapPropagator().Extract(ctx, propagation.HeaderCarrier(r.Header))
log.Println("The \"handle inner request\" span should be recorded, because it is recorded with a Tracer from the SDK TracerProvider")
_, span := tracer.Start(ctx, "handle inner request")
defer span.End()
// Do "backend work"
time.Sleep(time.Second)
}
// This handler will be a passthrough, since we didn't set a global TracerProvider
passthroughHandler := handler.New(backendFunc)
passthroughHandler.HandleHTTPReq(r)
}
func initPassthroughGlobals() {
// We explicitly DO NOT set the global TracerProvider using otel.SetTracerProvider().
// The unset TracerProvider returns a "non-recording" span, but still passes through context.
log.Println("Register a global TextMapPropagator, but do not register a global TracerProvider to be in \"passthrough\" mode.")
log.Println("The \"passthrough\" mode propagates the TraceContext and Baggage, but does not record spans.")
otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}))
}
// nonGlobalTracer creates a trace provider instance for testing, but doesn't
// set it as the global tracer provider.
func nonGlobalTracer() (*sdktrace.TracerProvider, error) {
exp, err := stdouttrace.New(stdouttrace.WithPrettyPrint())
if err != nil {
return nil, fmt.Errorf("failed to initialize stdouttrace exporter: %w", err)
}
bsp := sdktrace.NewBatchSpanProcessor(exp)
tp := sdktrace.NewTracerProvider(
sdktrace.WithSampler(sdktrace.AlwaysSample()),
sdktrace.WithSpanProcessor(bsp),
)
return tp, nil
}
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