108 lines
4.2 KiB
Java
108 lines
4.2 KiB
Java
/*
|
|
* Copyright 2019, OpenConsensus 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 openconsensus.trace.samplers;
|
|
|
|
import com.google.auto.value.AutoValue;
|
|
import java.util.List;
|
|
import javax.annotation.Nullable;
|
|
import javax.annotation.concurrent.Immutable;
|
|
import openconsensus.internal.Utils;
|
|
import openconsensus.trace.Sampler;
|
|
import openconsensus.trace.Span;
|
|
import openconsensus.trace.SpanContext;
|
|
import openconsensus.trace.SpanId;
|
|
import openconsensus.trace.TraceId;
|
|
|
|
/**
|
|
* We assume the lower 64 bits of the traceId's are randomly distributed around the whole (long)
|
|
* range. We convert an incoming probability into an upper bound on that value, such that we can
|
|
* just compare the absolute value of the id and the bound to see if we are within the desired
|
|
* probability range. Using the low bits of the traceId also ensures that systems that only use 64
|
|
* bit ID's will also work with this sampler.
|
|
*/
|
|
@AutoValue
|
|
@Immutable
|
|
abstract class ProbabilitySampler extends Sampler {
|
|
|
|
ProbabilitySampler() {}
|
|
|
|
abstract double getProbability();
|
|
|
|
abstract long getIdUpperBound();
|
|
|
|
/**
|
|
* Returns a new {@link ProbabilitySampler}. The probability of sampling a trace is equal to that
|
|
* of the specified probability.
|
|
*
|
|
* @param probability The desired probability of sampling. Must be within [0.0, 1.0].
|
|
* @return a new {@link ProbabilitySampler}.
|
|
* @throws IllegalArgumentException if {@code probability} is out of range
|
|
*/
|
|
static ProbabilitySampler create(double probability) {
|
|
Utils.checkArgument(
|
|
probability >= 0.0 && probability <= 1.0, "probability must be in range [0.0, 1.0]");
|
|
long idUpperBound;
|
|
// Special case the limits, to avoid any possible issues with lack of precision across
|
|
// double/long boundaries. For probability == 0.0, we use Long.MIN_VALUE as this guarantees
|
|
// that we will never sample a trace, even in the case where the id == Long.MIN_VALUE, since
|
|
// Math.Abs(Long.MIN_VALUE) == Long.MIN_VALUE.
|
|
if (probability == 0.0) {
|
|
idUpperBound = Long.MIN_VALUE;
|
|
} else if (probability == 1.0) {
|
|
idUpperBound = Long.MAX_VALUE;
|
|
} else {
|
|
idUpperBound = (long) (probability * Long.MAX_VALUE);
|
|
}
|
|
return new AutoValue_ProbabilitySampler(probability, idUpperBound);
|
|
}
|
|
|
|
@Override
|
|
public final boolean shouldSample(
|
|
@Nullable SpanContext parentContext,
|
|
@Nullable Boolean hasRemoteParent,
|
|
TraceId traceId,
|
|
SpanId spanId,
|
|
String name,
|
|
@Nullable List<Span> parentLinks) {
|
|
// If the parent is sampled keep the sampling decision.
|
|
if (parentContext != null && parentContext.getTraceOptions().isSampled()) {
|
|
return true;
|
|
}
|
|
if (parentLinks != null) {
|
|
// If any parent link is sampled keep the sampling decision.
|
|
for (Span parentLink : parentLinks) {
|
|
if (parentLink.getContext().getTraceOptions().isSampled()) {
|
|
return true;
|
|
}
|
|
}
|
|
}
|
|
// Always sample if we are within probability range. This is true even for child spans (that
|
|
// may have had a different sampling decision made) to allow for different sampling policies,
|
|
// and dynamic increases to sampling probabilities for debugging purposes.
|
|
// Note use of '<' for comparison. This ensures that we never sample for probability == 0.0,
|
|
// while allowing for a (very) small chance of *not* sampling if the id == Long.MAX_VALUE.
|
|
// This is considered a reasonable tradeoff for the simplicity/performance requirements (this
|
|
// code is executed in-line for every Span creation).
|
|
return Math.abs(traceId.getLowerLong()) < getIdUpperBound();
|
|
}
|
|
|
|
@Override
|
|
public final String getDescription() {
|
|
return String.format("ProbabilitySampler{%.6f}", getProbability());
|
|
}
|
|
}
|