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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package handler // import "go.opentelemetry.io/contrib/examples/passthrough/handler"
import (
"context"
"log"
"net/http"
"time"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/propagation"
"go.opentelemetry.io/otel/trace"
)
// Handler is a minimal implementation of the handler and client from
// go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp for demonstration purposes.
// It handles an incoming http request, and makes an outgoing http request.
type Handler struct {
propagators propagation.TextMapPropagator
tracer trace.Tracer
next func(r *http.Request)
}
// New returns a new Handler that will trace requests before handing them off
// to next.
func New(next func(r *http.Request)) *Handler {
// Like most instrumentation packages, this handler defaults to using the
// global propagators and tracer providers.
return &Handler{
propagators: otel.GetTextMapPropagator(),
tracer: otel.Tracer("go.opentelemetry.io/contrib/examples/passthrough/handler"),
next: next,
}
}
// HandleHTTPReq mimics what an instrumented http server does.
func (h *Handler) HandleHTTPReq(r *http.Request) {
ctx := h.propagators.Extract(r.Context(), propagation.HeaderCarrier(r.Header))
var span trace.Span
log.Println("The \"handle passthrough request\" span should NOT be recorded, because it is recorded by a TracerProvider not backed by the SDK.")
ctx, span = h.tracer.Start(ctx, "handle passthrough request")
defer span.End()
// Pretend to do work
time.Sleep(time.Second)
h.makeOutgoingRequest(ctx)
}
// makeOutgoingRequest mimics what an instrumented http client does.
func (h *Handler) makeOutgoingRequest(ctx context.Context) {
// make a new http request
r, err := http.NewRequest("", "", nil)
if err != nil {
panic(err)
}
log.Println("The \"make outgoing request from passthrough\" span should NOT be recorded, because it is recorded by a TracerProvider not backed by the SDK.")
ctx, span := h.tracer.Start(ctx, "make outgoing request from passthrough")
defer span.End()
r = r.WithContext(ctx)
h.propagators.Inject(ctx, propagation.HeaderCarrier(r.Header))
h.next(r)
}
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