mirror of https://github.com/hashicorp/consul
76 lines
2.2 KiB
Go
76 lines
2.2 KiB
Go
// Copyright 2017, 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 trace
|
|
|
|
import (
|
|
"encoding/binary"
|
|
)
|
|
|
|
const defaultSamplingProbability = 1e-4
|
|
|
|
// Sampler decides whether a trace should be sampled and exported.
|
|
type Sampler func(SamplingParameters) SamplingDecision
|
|
|
|
// SamplingParameters contains the values passed to a Sampler.
|
|
type SamplingParameters struct {
|
|
ParentContext SpanContext
|
|
TraceID TraceID
|
|
SpanID SpanID
|
|
Name string
|
|
HasRemoteParent bool
|
|
}
|
|
|
|
// SamplingDecision is the value returned by a Sampler.
|
|
type SamplingDecision struct {
|
|
Sample bool
|
|
}
|
|
|
|
// ProbabilitySampler returns a Sampler that samples a given fraction of traces.
|
|
//
|
|
// It also samples spans whose parents are sampled.
|
|
func ProbabilitySampler(fraction float64) Sampler {
|
|
if !(fraction >= 0) {
|
|
fraction = 0
|
|
} else if fraction >= 1 {
|
|
return AlwaysSample()
|
|
}
|
|
|
|
traceIDUpperBound := uint64(fraction * (1 << 63))
|
|
return Sampler(func(p SamplingParameters) SamplingDecision {
|
|
if p.ParentContext.IsSampled() {
|
|
return SamplingDecision{Sample: true}
|
|
}
|
|
x := binary.BigEndian.Uint64(p.TraceID[0:8]) >> 1
|
|
return SamplingDecision{Sample: x < traceIDUpperBound}
|
|
})
|
|
}
|
|
|
|
// AlwaysSample returns a Sampler that samples every trace.
|
|
// Be careful about using this sampler in a production application with
|
|
// significant traffic: a new trace will be started and exported for every
|
|
// request.
|
|
func AlwaysSample() Sampler {
|
|
return func(p SamplingParameters) SamplingDecision {
|
|
return SamplingDecision{Sample: true}
|
|
}
|
|
}
|
|
|
|
// NeverSample returns a Sampler that samples no traces.
|
|
func NeverSample() Sampler {
|
|
return func(p SamplingParameters) SamplingDecision {
|
|
return SamplingDecision{Sample: false}
|
|
}
|
|
}
|