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spanref.go
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spanref.go
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// Copyright (c) 2017 Uber Technologies, 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 model
import (
"fmt"
)
// SpanRefType describes the type of a span reference
type SpanRefType int
const (
// ChildOf span reference type describes a reference to a parent span
// that depends on the response from the current (child) span
ChildOf SpanRefType = iota
// FollowsFrom span reference type describes a reference to a "parent" span
// that does not depend on the response from the current (child) span
FollowsFrom
childOfStr = "child-of"
followsFromStr = "follows-from"
)
// SpanRef describes a reference from one span to another
type SpanRef struct {
RefType SpanRefType `json:"refType"`
TraceID TraceID `json:"traceID"`
SpanID SpanID `json:"spanID"`
}
func (p SpanRefType) String() string {
switch p {
case ChildOf:
return childOfStr
case FollowsFrom:
return followsFromStr
}
return "<invalid>"
}
// SpanRefTypeFromString converts a string into SpanRefType enum.
func SpanRefTypeFromString(s string) (SpanRefType, error) {
switch s {
case childOfStr:
return ChildOf, nil
case followsFromStr:
return FollowsFrom, nil
}
return SpanRefType(0), fmt.Errorf("not a valid SpanRefType string %s", s)
}
// MarshalText allows SpanRefType to serialize itself in JSON as a string.
func (p SpanRefType) MarshalText() ([]byte, error) {
return []byte(p.String()), nil
}
// UnmarshalText allows SpanRefType to deserialize itself from a JSON string.
func (p *SpanRefType) UnmarshalText(text []byte) error {
q, err := SpanRefTypeFromString(string(text))
if err != nil {
return err
}
*p = q
return nil
}
// MaybeAddParentSpanID adds non-zero parentSpanID to refs as a child-of reference.
// We no longer store ParentSpanID in the domain model, but the data in the database
// or other formats might still have these IDs without representing them in the References,
// so this converts parent IDs to canonical reference format.
func MaybeAddParentSpanID(traceID TraceID, parentSpanID SpanID, refs []SpanRef) []SpanRef {
if parentSpanID == 0 {
return refs
}
for i := range refs {
r := &refs[i]
if r.SpanID == parentSpanID && r.TraceID == traceID && r.RefType == ChildOf {
return refs
}
}
newRef := SpanRef{
TraceID: traceID,
SpanID: parentSpanID,
RefType: ChildOf,
}
if len(refs) == 0 {
return append(refs, newRef)
}
newRefs := make([]SpanRef, len(refs)+1)
newRefs[0] = newRef
copy(newRefs[1:], refs)
return newRefs
}
// NewChildOfRef creates a new child-of span reference.
func NewChildOfRef(traceID TraceID, spanID SpanID) SpanRef {
return SpanRef{
RefType: ChildOf,
TraceID: traceID,
SpanID: spanID,
}
}
// NewFollowsFromRef creates a new follows-from span reference.
func NewFollowsFromRef(traceID TraceID, spanID SpanID) SpanRef {
return SpanRef{
RefType: FollowsFrom,
TraceID: traceID,
SpanID: spanID,
}
}