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// Copyright 2018, OpenCensus Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ochttp
import (
"context"
"io"
"net/http"
"strconv"
"sync"
"time"
"go.opencensus.io/stats"
"go.opencensus.io/tag"
)
// statsTransport is an http.RoundTripper that collects stats for the outgoing requests.
type statsTransport struct {
base http.RoundTripper
}
// RoundTrip implements http.RoundTripper, delegating to Base and recording stats for the request.
func (t statsTransport) RoundTrip(req *http.Request) (*http.Response, error) {
ctx, _ := tag.New(req.Context(),
tag.Upsert(Host, req.URL.Host),
tag.Upsert(Path, req.URL.Path),
tag.Upsert(Method, req.Method))
req = req.WithContext(ctx)
track := &tracker{
start: time.Now(),
ctx: ctx,
}
if req.Body == nil {
// TODO: Handle cases where ContentLength is not set.
track.reqSize = -1
} else if req.ContentLength > 0 {
track.reqSize = req.ContentLength
}
stats.Record(ctx, ClientRequestCount.M(1))
// Perform request.
resp, err := t.base.RoundTrip(req)
if err != nil {
track.statusCode = http.StatusInternalServerError
track.end()
} else {
track.statusCode = resp.StatusCode
if resp.Body == nil {
track.end()
} else {
track.body = resp.Body
resp.Body = track
}
}
return resp, err
}
// CancelRequest cancels an in-flight request by closing its connection.
func (t statsTransport) CancelRequest(req *http.Request) {
type canceler interface {
CancelRequest(*http.Request)
}
if cr, ok := t.base.(canceler); ok {
cr.CancelRequest(req)
}
}
type tracker struct {
ctx context.Context
respSize int64
reqSize int64
start time.Time
body io.ReadCloser
statusCode int
endOnce sync.Once
}
var _ io.ReadCloser = (*tracker)(nil)
func (t *tracker) end() {
t.endOnce.Do(func() {
m := []stats.Measurement{
ClientLatency.M(float64(time.Since(t.start)) / float64(time.Millisecond)),
ClientResponseBytes.M(t.respSize),
}
if t.reqSize >= 0 {
m = append(m, ClientRequestBytes.M(t.reqSize))
}
ctx, _ := tag.New(t.ctx, tag.Upsert(StatusCode, strconv.Itoa(t.statusCode)))
stats.Record(ctx, m...)
})
}
func (t *tracker) Read(b []byte) (int, error) {
n, err := t.body.Read(b)
switch err {
case nil:
t.respSize += int64(n)
return n, nil
case io.EOF:
t.end()
}
return n, err
}
func (t *tracker) Close() error {
// Invoking endSpan on Close will help catch the cases
// in which a read returned a non-nil error, we set the
// span status but didn't end the span.
t.end()
return t.body.Close()
}
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