How to use

CollectorSampler

in

zipkin2.collector

@Override
public String toString() {
 return "CollectorSampler(" + boundary() + ")";
}

@Bean
@ConditionalOnMissingBean(CollectorSampler.class)
CollectorSampler traceIdSampler(@Value("${zipkin.collector.sample-rate:1.0}") float rate) {
 return CollectorSampler.create(rate);
}

List<Span> sample(List<Span> input) {
 List<Span> sampled = new ArrayList<>(input.size());
 for (int i = 0, length = input.size(); i < length; i++) {
  Span s = input.get(i);
  if (sampler.isSampled(s.traceId(), Boolean.TRUE.equals(s.debug()))) {
   sampled.add(s);
  }
 }
 int dropped = input.size() - sampled.size();
 if (dropped > 0) metrics.incrementSpansDropped(dropped);
 return sampled;
}

/**
 * Returns true if spans with this trace ID should be recorded to storage.
 *
 * <p>Zipkin v1 allows storage-layer sampling, which can help prevent spikes in traffic from
 * overloading the system. Debug spans are always stored.
 *
 * <p>This uses only the lower 64 bits of the trace ID as instrumentation still send mixed trace
 * ID width.
 *
 * @param hexTraceId the lower 64 bits of the span's trace ID are checked against the boundary
 * @param debug when true, always passes sampling
 */
public boolean isSampled(String hexTraceId, boolean debug) {
 if (Boolean.TRUE.equals(debug)) return true;
 long traceId = HexCodec.lowerHexToUnsignedLong(hexTraceId);
 // The absolute value of Long.MIN_VALUE is larger than a long, so Math.abs returns identity.
 // This converts to MAX_VALUE to avoid always dropping when traceId == Long.MIN_VALUE
 long t = traceId == Long.MIN_VALUE ? Long.MAX_VALUE : Math.abs(traceId);
 return t <= boundary();
}