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trace.go
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trace.go
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// Copyright 2020 lack
//
// 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 provides an interface for distributed tracing
package trace
import (
"context"
"time"
"github.com/lack-io/vine/util/context/metadata"
)
// Tracer is an interface for distributed tracing
type Tracer interface {
// Start a trace
Start(ctx context.Context, name string) (context.Context, *Span)
// Finish the trace
Finish(*Span) error
// Read the traces
Read(...ReadOption) ([]*Span, error)
}
// SpanType describe the nature of the trace span
type SpanType int
const (
// SpanTypeRequestInbound is a span created when serving a request
SpanTypeRequestInbound SpanType = iota
// SpanTypeRequestOutbound is a span created when making a service call
SpanTypeRequestOutbound
)
// Span is used to record an entry
type Span struct {
// Id of the trace
Trace string
// name of the span
Name string
// id of the span
Id string
// parent span id
Parent string
// Start time
Started time.Time
// Duration in nano seconds
Duration time.Duration
// associated data
Metadata map[string]string
// Type
Type SpanType
}
const (
traceIDKey = "Vine-Trace-Id"
spanIDKey = "Vine-Span-Id"
)
// FromContext returns a span from context
func FromContext(ctx context.Context) (traceID string, parentSpanID string, isFound bool) {
traceID, traceOk := metadata.Get(ctx, traceIDKey)
vineID, vineOk := metadata.Get(ctx, "Vine-Id")
if !traceOk && !vineOk {
isFound = false
return
}
if !traceOk {
traceID = vineID
}
parentSpanID, ok := metadata.Get(ctx, spanIDKey)
return traceID, parentSpanID, ok
}
// ToContext saves the trace and span ids in the context
func ToContext(ctx context.Context, traceID, parentSpanID string) context.Context {
return metadata.MergeContext(ctx, map[string]string{
traceIDKey: traceID,
spanIDKey: parentSpanID,
}, true)
}
var (
DefaultTracer Tracer = new(noop)
)
type noop struct{}
func (n *noop) Init(...Option) error {
return nil
}
func (n *noop) Start(ctx context.Context, name string) (context.Context, *Span) {
return nil, nil
}
func (n *noop) Finish(*Span) error {
return nil
}
func (n *noop) Read(...ReadOption) ([]*Span, error) {
return nil, nil
}