98 lines
3 KiB
Go
98 lines
3 KiB
Go
// Copyright 2018, OpenCensus Authors
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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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package ochttp
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import (
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"net/http"
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"go.opencensus.io/trace"
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"go.opencensus.io/trace/propagation"
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)
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// Transport is an http.RoundTripper that instruments all outgoing requests with
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// OpenCensus stats and tracing.
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//
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// The zero value is intended to be a useful default, but for
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// now it's recommended that you explicitly set Propagation, since the default
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// for this may change.
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type Transport struct {
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// Base may be set to wrap another http.RoundTripper that does the actual
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// requests. By default http.DefaultTransport is used.
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//
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// If base HTTP roundtripper implements CancelRequest,
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// the returned round tripper will be cancelable.
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Base http.RoundTripper
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// Propagation defines how traces are propagated. If unspecified, a default
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// (currently B3 format) will be used.
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Propagation propagation.HTTPFormat
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// StartOptions are applied to the span started by this Transport around each
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// request.
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//
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// StartOptions.SpanKind will always be set to trace.SpanKindClient
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// for spans started by this transport.
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StartOptions trace.StartOptions
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// NameFromRequest holds the function to use for generating the span name
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// from the information found in the outgoing HTTP Request. By default the
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// name equals the URL Path.
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FormatSpanName func(*http.Request) string
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// TODO: Implement tag propagation for HTTP.
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}
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// RoundTrip implements http.RoundTripper, delegating to Base and recording stats and traces for the request.
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func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
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rt := t.base()
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// TODO: remove excessive nesting of http.RoundTrippers here.
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format := t.Propagation
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if format == nil {
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format = defaultFormat
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}
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spanNameFormatter := t.FormatSpanName
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if spanNameFormatter == nil {
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spanNameFormatter = spanNameFromURL
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}
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rt = &traceTransport{
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base: rt,
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format: format,
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startOptions: trace.StartOptions{
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Sampler: t.StartOptions.Sampler,
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SpanKind: trace.SpanKindClient,
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},
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formatSpanName: spanNameFormatter,
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}
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rt = statsTransport{base: rt}
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return rt.RoundTrip(req)
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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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// 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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