tidb util 源码
tidb util 代码
文件路径：/util/tracing/util.go
// Copyright 2018 PingCAP, 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 tracing
import (
"context"
"github.com/opentracing/basictracer-go"
"github.com/opentracing/opentracing-go"
)
// TiDBTrace is set as Baggage on traces which are used for tidb tracing.
const TiDBTrace = "tr"
// A CallbackRecorder immediately invokes itself on received trace spans.
type CallbackRecorder func(sp basictracer.RawSpan)
// RecordSpan implements basictracer.SpanRecorder.
func (cr CallbackRecorder) RecordSpan(sp basictracer.RawSpan) {
cr(sp)
}
// NewRecordedTrace returns a Span which records directly via the specified
// callback.
func NewRecordedTrace(opName string, callback func(sp basictracer.RawSpan)) opentracing.Span {
tr := basictracer.New(CallbackRecorder(callback))
opentracing.SetGlobalTracer(tr)
sp := tr.StartSpan(opName)
sp.SetBaggageItem(TiDBTrace, "1")
return sp
}
// noopSpan returns a Span which discards all operations.
func noopSpan() opentracing.Span {
return (opentracing.NoopTracer{}).StartSpan("DefaultSpan")
}
// SpanFromContext returns the span obtained from the context or, if none is found, a new one started through tracer.
func SpanFromContext(ctx context.Context) (sp opentracing.Span) {
if sp = opentracing.SpanFromContext(ctx); sp == nil {
return noopSpan()
}
return sp
}
// ChildSpanFromContxt return a non-nil span. If span can be got from ctx, then returned span is
// a child of such span. Otherwise, returned span is a noop span.
func ChildSpanFromContxt(ctx context.Context, opName string) (opentracing.Span, context.Context) {
if sp := opentracing.SpanFromContext(ctx); sp != nil {
if _, ok := sp.Tracer().(opentracing.NoopTracer); !ok {
child := opentracing.StartSpan(opName, opentracing.ChildOf(sp.Context()))
return child, opentracing.ContextWithSpan(ctx, child)
}
}
return noopSpan(), ctx
}
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