Module: OpenCensus::Trace::Samplers

Defined in:


A sampler determines whether a given request's latency trace should actually be reported. It is usually not necessary to trace every request, especially for an application serving heavy traffic. You may use a sampler to decide, for a given request, whether to report its trace.

The OpenCensus specification defines four samplers: AlwaysSample, NeverSample, Probability, and RateLimiting.

A sampler is a Proc that takes a hash of environment information and returns a boolean indicating whether or not to sample the current request. Alternately, it could be an object that duck-types the Proc interface by implementing the call method. The hash passed to call may contain the following keys, all of which are optional. Samplers must adjust their behavior to account for the availability or absence of any environment information:

  • span_context The SpanContext that created the span being sampled.
  • rack_env The hash of Rack environment information

Applications may set a default sampler in the config. In addition, the sampler may be overridden whenever a span is created.

Defined Under Namespace

Classes: AlwaysSample, NeverSample, Probability, RateLimiting

Constant Summary collapse

MaxQPS =

MaxQPS is an older, deprecated name for the RateLimiting sampler.