brave.sampler.Sampler Maven / Gradle / Ivy
package brave.sampler;
/**
* Sampler is responsible for deciding if a particular trace should be "sampled", i.e. whether the
* overhead of tracing will occur and/or if a trace will be reported to the collection tier.
*
* Zipkin v1 uses before-the-fact sampling. This means that the decision to keep or drop the
* trace is made before any work is measured, or annotations are added. As such, the input parameter
* to zipkin v1 samplers is the trace ID (lower 64-bits under the assumption all bits are random).
*
*
The instrumentation sampling decision happens once, at the root of the trace, and is
* propagated downstream. For this reason, the algorithm needn't be consistent based on trace ID.
*/
// abstract for factory-method support on Java language level 7
public abstract class Sampler {
public static final Sampler ALWAYS_SAMPLE = new Sampler() {
@Override public boolean isSampled(long traceId) {
return true;
}
@Override public String toString() {
return "AlwaysSample";
}
};
public static final Sampler NEVER_SAMPLE = new Sampler() {
@Override public boolean isSampled(long traceId) {
return false;
}
@Override public String toString() {
return "NeverSample";
}
};
/** Returns true if the trace ID should be measured. */
public abstract boolean isSampled(long traceId);
/**
* Returns a sampler, given a rate expressed as a percentage.
*
*
The sampler returned is good for low volumes of traffic (<100K requests), as it is precise.
* If you have high volumes of traffic, consider {@link BoundarySampler}.
*
* @param rate minimum sample rate is 0.01, or 1% of traces
*/
public static Sampler create(float rate) {
return CountingSampler.create(rate);
}
}