// 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 (
"io"
"net/http"
"net/http/httptrace"
"go.opencensus.io/plugin/ochttp/propagation/b3"
"go.opencensus.io/trace"
"go.opencensus.io/trace/propagation"
)
// TODO(jbd): Add godoc examples.
var defaultFormat propagation.HTTPFormat = &b3.HTTPFormat{}
// Attributes recorded on the span for the requests.
// Only trace exporters will need them.
const (
HostAttribute = "http.host"
MethodAttribute = "http.method"
PathAttribute = "http.path"
UserAgentAttribute = "http.user_agent"
StatusCodeAttribute = "http.status_code"
)
type traceTransport struct {
base http.RoundTripper
startOptions trace.StartOptions
format propagation.HTTPFormat
formatSpanName func(*http.Request) string
newClientTrace func(*http.Request, *trace.Span) *httptrace.ClientTrace
}
// TODO(jbd): Add message events for request and response size.
// RoundTrip creates a trace.Span and inserts it into the outgoing request's headers.
// The created span can follow a parent span, if a parent is presented in
// the request's context.
func (t *traceTransport) RoundTrip(req *http.Request) (*http.Response, error) {
name := t.formatSpanName(req)
// TODO(jbd): Discuss whether we want to prefix
// outgoing requests with Sent.
ctx, span := trace.StartSpan(req.Context(), name,
trace.WithSampler(t.startOptions.Sampler),
trace.WithSpanKind(trace.SpanKindClient))
if t.newClientTrace != nil {
req = req.WithContext(httptrace.WithClientTrace(ctx, t.newClientTrace(req, span)))
} else {
req = req.WithContext(ctx)
}
if t.format != nil {
// SpanContextToRequest will modify its Request argument, which is
// contrary to the contract for http.RoundTripper, so we need to
// pass it a copy of the Request.
// However, the Request struct itself was already copied by
// the WithContext calls above and so we just need to copy the header.
header := make(http.Header)
for k, v := range req.Header {
header[k] = v
}
req.Header = header
t.format.SpanContextToRequest(span.SpanContext(), req)
}
span.AddAttributes(requestAttrs(req)...)
resp, err := t.base.RoundTrip(req)
if err != nil {
span.SetStatus(trace.Status{Code: trace.StatusCodeUnknown, Message: err.Error()})
span.End()
return resp, err
}
span.AddAttributes(responseAttrs(resp)...)
span.SetStatus(TraceStatus(resp.StatusCode, resp.Status))
// span.End() will be invoked after
// a read from resp.Body returns io.EOF or when
// resp.Body.Close() is invoked.
resp.Body = &bodyTracker{rc: resp.Body, span: span}
return resp, err
}
// bodyTracker wraps a response.Body and invokes
// trace.EndSpan on encountering io.EOF on reading
// the body of the original response.
type bodyTracker struct {
rc io.ReadCloser
span *trace.Span
}
var _ io.ReadCloser = (*bodyTracker)(nil)
func (bt *bodyTracker) Read(b []byte) (int, error) {
n, err := bt.rc.Read(b)
switch err {
case nil:
return n, nil
case io.EOF:
bt.span.End()
default:
// For all other errors, set the span status
bt.span.SetStatus(trace.Status{
// Code 2 is the error code for Internal server error.
Code: 2,
Message: err.Error(),
})
}
return n, err
}
func (bt *bodyTracker) 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.
bt.span.End()
return bt.rc.Close()
}
// CancelRequest cancels an in-flight request by closing its connection.
func (t *traceTransport) CancelRequest(req *http.Request) {
type canceler interface {
CancelRequest(*http.Request)
}
if cr, ok := t.base.(canceler); ok {
cr.CancelRequest(req)
}
}
func spanNameFromURL(req *http.Request) string {
return req.URL.Path
}
func requestAttrs(r *http.Request) []trace.Attribute {
return []trace.Attribute{
trace.StringAttribute(PathAttribute, r.URL.Path),
trace.StringAttribute(HostAttribute, r.URL.Host),
trace.StringAttribute(MethodAttribute, r.Method),
trace.StringAttribute(UserAgentAttribute, r.UserAgent()),
}
}
func responseAttrs(resp *http.Response) []trace.Attribute {
return []trace.Attribute{
trace.Int64Attribute(StatusCodeAttribute, int64(resp.StatusCode)),
}
}
// TraceStatus is a utility to convert the HTTP status code to a trace.Status that
// represents the outcome as closely as possible.
func TraceStatus(httpStatusCode int, statusLine string) trace.Status {
var code int32
if httpStatusCode < 200 || httpStatusCode >= 400 {
code = trace.StatusCodeUnknown
}
switch httpStatusCode {
case 499:
code = trace.StatusCodeCancelled
case http.StatusBadRequest:
code = trace.StatusCodeInvalidArgument
case http.StatusGatewayTimeout:
code = trace.StatusCodeDeadlineExceeded
case http.StatusNotFound:
code = trace.StatusCodeNotFound
case http.StatusForbidden:
code = trace.StatusCodePermissionDenied
case http.StatusUnauthorized: // 401 is actually unauthenticated.
code = trace.StatusCodeUnauthenticated
case http.StatusTooManyRequests:
code = trace.StatusCodeResourceExhausted
case http.StatusNotImplemented:
code = trace.StatusCodeUnimplemented
case http.StatusServiceUnavailable:
code = trace.StatusCodeUnavailable
case http.StatusOK:
code = trace.StatusCodeOK
}
return trace.Status{Code: code, Message: codeToStr[code]}
}
var codeToStr = map[int32]string{
trace.StatusCodeOK: `OK`,
trace.StatusCodeCancelled: `CANCELLED`,
trace.StatusCodeUnknown: `UNKNOWN`,
trace.StatusCodeInvalidArgument: `INVALID_ARGUMENT`,
trace.StatusCodeDeadlineExceeded: `DEADLINE_EXCEEDED`,
trace.StatusCodeNotFound: `NOT_FOUND`,
trace.StatusCodeAlreadyExists: `ALREADY_EXISTS`,
trace.StatusCodePermissionDenied: `PERMISSION_DENIED`,
trace.StatusCodeResourceExhausted: `RESOURCE_EXHAUSTED`,
trace.StatusCodeFailedPrecondition: `FAILED_PRECONDITION`,
trace.StatusCodeAborted: `ABORTED`,
trace.StatusCodeOutOfRange: `OUT_OF_RANGE`,
trace.StatusCodeUnimplemented: `UNIMPLEMENTED`,
trace.StatusCodeInternal: `INTERNAL`,
trace.StatusCodeUnavailable: `UNAVAILABLE`,
trace.StatusCodeDataLoss: `DATA_LOSS`,
trace.StatusCodeUnauthenticated: `UNAUTHENTICATED`,
}
func isHealthEndpoint(path string) bool {
// Health checking is pretty frequent and
// traces collected for health endpoints
// can be extremely noisy and expensive.
// Disable canonical health checking endpoints
// like /healthz and /_ah/health for now.
if path == "/healthz" || path == "/_ah/health" {
return true
}
return false
}
