handler.go

package main

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

	"github.com/pkg/errors"
	"github.com/uber/tchannel-go"
	thttp "github.com/uber/tchannel-go/http"
)

type handler struct {
	sc *tchannel.SubChannel
}

func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if err := h.handleRequest(w, r); err != nil {
		log.Printf("Failed to handle request: %v", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

func (h handler) handleRequest(w http.ResponseWriter, r *http.Request) error {
	ctx, cancel := tchannel.NewContext(300 * time.Second)
	defer cancel()

	call, err := h.sc.BeginCall(ctx, "_pprof", &tchannel.CallOptions{
		Format: tchannel.HTTP,
	})
	if err != nil {
		return errors.Wrap(err, "Failed to start call to _pprof")
	}

	if err := thttp.WriteRequest(call, r); err != nil {
		return errors.Wrap(err, "failed to write HTTP request to TChannel")
	}

	resp, err := thttp.ReadResponse(call.Response())
	if err != nil {
		return errors.Wrap(err, "failed to read HTTP response from TChannel")
	}
	defer resp.Body.Close()

	for k, vs := range resp.Header {
		for _, v := range vs {
			w.Header().Add(k, v)
		}
	}
	w.WriteHeader(resp.StatusCode)

	if _, err := io.Copy(w, resp.Body); err != nil {
		return errors.Wrap(err, "failed to copy HTTP response body from TChannel")
	}

	return nil
}