Class: Datadog::Tracing::Sampling::Span::Rule

Inherits:
Object
  • Object
show all
Defined in:
lib/datadog/tracing/sampling/span/rule.rb

Overview

Span sampling rule that applies a sampling rate if the span matches the provided Matcher. Additionally, a rate limiter is also applied.

If a span does not conform to the matcher, no changes are made.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(matcher, sample_rate: Span::Ext::DEFAULT_SAMPLE_RATE, rate_limit: Span::Ext::DEFAULT_MAX_PER_SECOND) ⇒ Rule

Creates a new span sampling rule.

Parameters:

  • matcher (Sampling::Span::Matcher) —

    whether this rule applies to a specific span

  • sample_rate (Float) (defaults to: Span::Ext::DEFAULT_SAMPLE_RATE) —

    span sampling ratio, between 0.0 (0%) and 1.0 (100%).

  • rate_limit (Numeric) (defaults to: Span::Ext::DEFAULT_MAX_PER_SECOND) —

    maximum number of spans sampled per second. Negative numbers mean unlimited spans.



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# File 'lib/datadog/tracing/sampling/span/rule.rb', line 22

def initialize(
  matcher,
  sample_rate: Span::Ext::DEFAULT_SAMPLE_RATE,
  rate_limit: Span::Ext::DEFAULT_MAX_PER_SECOND
)

  @matcher = matcher
  @sample_rate = sample_rate
  @rate_limit = rate_limit

  @sampler = Sampling::RateSampler.new
  # Set the sample_rate outside of the initializer to allow for
  # zero to be a "drop all".
  # The RateSampler initializer enforces non-zero, falling back to 100% sampling
  # if zero is provided.
  @sampler.sample_rate = sample_rate
  @rate_limiter = Sampling::TokenBucket.new(rate_limit)
end

Instance Attribute Details

#matcher ⇒ Object (readonly)

Returns the value of attribute matcher.



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# File 'lib/datadog/tracing/sampling/span/rule.rb', line 15

def matcher
  @matcher
end

#rate_limit ⇒ Object (readonly)

Returns the value of attribute rate_limit.



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# File 'lib/datadog/tracing/sampling/span/rule.rb', line 15

def rate_limit
  @rate_limit
end

#sample_rate ⇒ Object (readonly)

Returns the value of attribute sample_rate.



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# File 'lib/datadog/tracing/sampling/span/rule.rb', line 15

def sample_rate
  @sample_rate
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/datadog/tracing/sampling/span/rule.rb', line 71

def ==(other)
  return super unless other.is_a?(Rule)

  matcher == other.matcher &&
    sample_rate == other.sample_rate &&
    rate_limit == other.rate_limit
end

#sample!(span_op) ⇒ :kept, ...

This method should only be invoked for spans that are part of a trace that has been dropped by trace-level sampling. Invoking it for other spans will cause incorrect sampling metrics to be reported by the Datadog App.

Returns ‘true` if the provided span is sampled. If the span is dropped due to sampling rate or rate limiting, it returns `false`.

Returns ‘nil` if the span did not meet the matching criteria by the provided matcher.

This method modifies the ‘span` if it matches the provided matcher.

Parameters:

Returns:

  • (:kept, :rejected) —

    should this span be sampled?

  • (:not_matched) —

    span did not satisfy the matcher, no changes are made to the span



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# File 'lib/datadog/tracing/sampling/span/rule.rb', line 58

def sample!(span_op)
  return :not_matched unless @matcher.match?(span_op)

  if @sampler.sample?(span_op) && @rate_limiter.allow?(1)
    span_op.set_metric(Span::Ext::TAG_MECHANISM, Sampling::Ext::Mechanism::SPAN_SAMPLING_RATE)
    span_op.set_metric(Span::Ext::TAG_RULE_RATE, @sample_rate)
    span_op.set_metric(Span::Ext::TAG_MAX_PER_SECOND, @rate_limit)
    :kept
  else
    :rejected
  end
end