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request.go
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request.go
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// Copyright (C) 2014 Space Monkey, Inc.
//
// 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 trace
import (
"strconv"
)
// Request is a structure representing an incoming RPC request. Every field
// is optional.
type Request struct {
TraceId *int64
SpanId *int64
ParentId *int64
Sampled *bool
Flags *int64
}
// HeaderGetter is an interface that http.Header matches for RequestFromHeader
type HeaderGetter interface {
Get(string) string
}
// HeaderSetter is an interface that http.Header matches for Request.SetHeader
type HeaderSetter interface {
Set(string, string)
}
// RequestFromHeader will create a Request object given an http.Header or
// anything that matches the HeaderGetter interface.
func RequestFromHeader(header HeaderGetter) (rv Request) {
trace_id, err := fromHeader(header.Get("X-B3-TraceId"))
if err == nil {
rv.TraceId = &trace_id
}
span_id, err := fromHeader(header.Get("X-B3-SpanId"))
if err == nil {
rv.SpanId = &span_id
}
parent_id, err := fromHeader(header.Get("X-B3-ParentSpanId"))
if err == nil {
rv.ParentId = &parent_id
}
sampled, err := strconv.ParseBool(header.Get("X-B3-Sampled"))
if err == nil {
rv.Sampled = &sampled
}
rv.Sampled = &sampled
flags, err := fromHeader(header.Get("X-B3-Flags"))
if err == nil {
rv.Flags = &flags
}
return rv
}
// SetHeader will take a Request and fill out an http.Header, or anything that
// matches the HeaderSetter interface.
func (r Request) SetHeader(header HeaderSetter) {
if r.TraceId != nil {
header.Set("X-B3-TraceId", toHeader(*r.TraceId))
}
if r.SpanId != nil {
header.Set("X-B3-SpanId", toHeader(*r.SpanId))
}
if r.ParentId != nil {
header.Set("X-B3-ParentSpanId", toHeader(*r.ParentId))
}
if r.Sampled != nil {
header.Set("X-B3-Sampled", strconv.FormatBool(*r.Sampled))
}
if r.Flags != nil {
header.Set("X-B3-Flags", toHeader(*r.Flags))
}
}
// fromHeader reads a signed int64 that has been formatted as a hex uint64
func fromHeader(s string) (int64, error) {
v, err := strconv.ParseUint(s, 16, 64)
return int64(v), err
}
// toHeader writes a signed int64 as hex uint64
func toHeader(i int64) string {
return strconv.FormatUint(uint64(i), 16)
}