brave.sampler

Class BoundarySampler

java.lang.Object

brave.sampler.Sampler

brave.sampler.BoundarySampler

public final class BoundarySampler
extends Sampler

This sampler is appropriate for high-traffic instrumentation (ex edge web servers that each receive >100K requests) who provision random trace ids, and make the sampling decision only once. It defends against nodes in the cluster selecting exactly the same ids.

Implementation

This uses modulo 10000 arithmetic, which allows a minimum sample rate of 0.01%. Trace id collision was noticed in practice in the Twitter front-end cluster. A random salt is here to defend against nodes in the same cluster sampling exactly the same subset of trace ids. The goal was full 64-bit coverage of trace IDs on multi-host deployments.

Based on https://github.com/twitter/finagle/blob/develop/finagle-zipkin/src/main/scala/com/twitter/finagle/zipkin/thrift/Sampler.scala#L68

Field Summary

Fields inherited from class brave.sampler.Sampler

ALWAYS_SAMPLE, NEVER_SAMPLE

Method Summary

Modifier and Type	Method and Description
static Sampler	create(float rate)
boolean	isSampled(long traceId) Returns true when abs(traceId) <= boundary
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

create

public static Sampler create(float rate)

Parameters:

rate - 0 means never sample, 1 means always sample. Otherwise minimum sample rate is 0.0001, or 0.01% of traces

isSampled

public boolean isSampled(long traceId)

Returns true when abs(traceId) <= boundary

Specified by:

isSampled in class Sampler

toString

public String toString()

Overrides:

toString in class Object