mirror of
https://github.com/restic/restic.git
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105 lines
3.2 KiB
Go
105 lines
3.2 KiB
Go
// Copyright 2017 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build go1.7
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package trace
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import (
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"net/http"
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)
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// Transport is an http.RoundTripper that traces the outgoing requests.
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//
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// Transport is safe for concurrent usage.
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type Transport struct {
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// Base is the base http.RoundTripper to be used to do the actual request.
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//
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// Optional. If nil, http.DefaultTransport is used.
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Base http.RoundTripper
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}
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// RoundTrip creates a trace.Span and inserts it into the outgoing request's headers.
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// The created span can follow a parent span, if a parent is presented in
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// the request's context.
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func (t Transport) RoundTrip(req *http.Request) (*http.Response, error) {
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span := FromContext(req.Context()).NewRemoteChild(req)
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resp, err := t.base().RoundTrip(req)
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// TODO(jbd): Is it possible to defer the span.Finish?
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// In cases where RoundTrip panics, we still can finish the span.
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span.Finish(WithResponse(resp))
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return resp, err
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}
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// CancelRequest cancels an in-flight request by closing its connection.
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func (t Transport) CancelRequest(req *http.Request) {
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type canceler interface {
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CancelRequest(*http.Request)
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}
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if cr, ok := t.base().(canceler); ok {
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cr.CancelRequest(req)
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}
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}
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func (t Transport) base() http.RoundTripper {
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if t.Base != nil {
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return t.Base
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}
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return http.DefaultTransport
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}
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// HTTPHandler returns a http.Handler from the given handler
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// that is aware of the incoming request's span.
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// The span can be extracted from the incoming request in handler
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// functions from incoming request's context:
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//
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// span := trace.FromContext(r.Context())
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//
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// The span will be auto finished by the handler.
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func (c *Client) HTTPHandler(h http.Handler) http.Handler {
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return &handler{traceClient: c, handler: h}
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}
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type handler struct {
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traceClient *Client
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handler http.Handler
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}
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func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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traceID, parentSpanID, options, optionsOk, ok := traceInfoFromHeader(r.Header.Get(httpHeader))
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if !ok {
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traceID = nextTraceID()
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}
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t := &trace{
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traceID: traceID,
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client: h.traceClient,
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globalOptions: options,
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localOptions: options,
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}
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span := startNewChildWithRequest(r, t, parentSpanID)
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span.span.Kind = spanKindServer
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span.rootSpan = true
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configureSpanFromPolicy(span, h.traceClient.policy, ok)
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defer span.Finish()
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r = r.WithContext(NewContext(r.Context(), span))
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if ok && !optionsOk {
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// Inject the trace context back to the response with the sampling options.
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// TODO(jbd): Remove when there is a better way to report the client's sampling.
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w.Header().Set(httpHeader, spanHeader(traceID, parentSpanID, span.trace.localOptions))
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}
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h.handler.ServeHTTP(w, r)
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}
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