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 (
	
)

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 ( float64) Sampler {
	if !( >= 0) {
		 = 0
	} else if  >= 1 {
		return AlwaysSample()
	}

	 := uint64( * (1 << 63))
	return Sampler(func( SamplingParameters) SamplingDecision {
		if .ParentContext.IsSampled() {
			return SamplingDecision{Sample: true}
		}
		 := binary.BigEndian.Uint64(.TraceID[0:8]) >> 1
		return SamplingDecision{Sample:  < }
	})
}
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 () Sampler {
	return func( SamplingParameters) SamplingDecision {
		return SamplingDecision{Sample: true}
	}
}
NeverSample returns a Sampler that samples no traces.
func () Sampler {
	return func( SamplingParameters) SamplingDecision {
		return SamplingDecision{Sample: false}
	}