Class: OpenCensus::Trace::Samplers::RateLimiting

Inherits:
Object
  • Object
show all
Defined in:
lib/opencensus/trace/samplers/rate_limiting.rb

Overview

The RateLimiting sampler delays a minimum amount of time between each sample, enforcing a maximum QPS across traces that use this sampler.

Constant Summary collapse

DEFAULT_RATE =

Default rate in samples per second.

0.1

Instance Method Summary collapse

Constructor Details

#initialize(qps = DEFAULT_RATE, rng: nil, time_class: nil) ⇒ RateLimiting

Create a sampler for the given QPS.

Parameters:

  • qps (Number) (defaults to: DEFAULT_RATE) —

    Samples per second. Default is DEFAULT_RATE.

  • rng (#rand) (defaults to: nil) —

    The random number generator to use. Default is a new ::Random instance.

  • time_class (#now) (defaults to: nil) —

    The time class to use. Default is ::Time. Generally used for testing.



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# File 'lib/opencensus/trace/samplers/rate_limiting.rb', line 40

def initialize qps = DEFAULT_RATE, rng: nil, time_class: nil
  @qps = qps
  @time_class = time_class || Time
  @rng = rng || Random.new
  @last_time = @time_class.now.to_f
  @lock = Monitor.new
end

Instance Method Details

#call(opts = {}) ⇒ boolean

Implements the sampler contract. Checks to see whether a sample should be taken at this time.

Parameters:

  • opts (Hash) (defaults to: {}) —

    The options to sample with.

Options Hash (opts):

  • :span_context (SpanContext) —

    If provided, the span context will be checked and the parent's sampling decision will be propagated if the parent was sampled.

Returns:

  • (boolean) —

    Whether to sample at this time.



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# File 'lib/opencensus/trace/samplers/rate_limiting.rb', line 58

def call opts = {}
  span_context = opts[:span_context]
  return true if span_context && span_context.sampled?
  @lock.synchronize do
    time = @time_class.now.to_f
    elapsed = time - @last_time
    @last_time = time
    @rng.rand <= elapsed * @qps
  end
end