Module: LaunchDarkly::Impl::EvaluatorBucketing

Defined in:
lib/ldclient-rb/impl/evaluator_bucketing.rb

Overview

Encapsulates the logic for percentage rollouts.

Since:

  • 5.5.0

Class Method Summary collapse

Class Method Details

.bucket_context(context, context_kind, key, bucket_by, salt, seed) ⇒ Float?

Returns a context’s bucket value as a floating-point value in ‘[0, 1)`.

Parameters:

  • context (LDContext) —

    the context properties

  • context_kind (String, nil) —

    the context kind to match against

  • key (String) —

    the feature flag key (or segment key, if this is for a segment rule)

  • bucket_by (String|Symbol) —

    the name of the context attribute to be used for bucketing

  • salt (String) —

    the feature flag’s or segment’s salt value

Returns:

  • (Float, nil) —

    the bucket value, from 0 inclusive to 1 exclusive

Raises:

Since:

  • 5.5.0



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# File 'lib/ldclient-rb/impl/evaluator_bucketing.rb', line 54

def self.bucket_context(context, context_kind, key, bucket_by, salt, seed)
  matched_context = context.individual_context(context_kind || LaunchDarkly::LDContext::KIND_DEFAULT)
  return nil if matched_context.nil?

  reference = (context_kind.nil? || context_kind.empty?) ? Reference.create_literal(bucket_by) : Reference.create(bucket_by)
  raise InvalidReferenceException.new(reference.error) unless reference.error.nil?

  context_value = matched_context.get_value_for_reference(reference)
  return 0.0 if context_value.nil?

  id_hash = bucketable_string_value(context_value)
  return 0.0 if id_hash.nil?

  if seed
    hash_key = "%d.%s" % [seed, id_hash]
  else
    hash_key = "%s.%s.%s" % [key, salt, id_hash]
  end

  hash_val = Digest::SHA1.hexdigest(hash_key)[0..14]
  hash_val.to_i(16) / Float(0xFFFFFFFFFFFFFFF)
end

.variation_index_for_context(flag, vr, context) ⇒ Array<[Number, nil], Boolean>

Applies either a fixed variation or a rollout for a rule (or the fallthrough rule).

Parameters:

Returns:

  • (Array<[Number, nil], Boolean>) —

    the variation index, or nil if there is an error

Raises:

Since:

  • 5.5.0



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# File 'lib/ldclient-rb/impl/evaluator_bucketing.rb', line 12

def self.variation_index_for_context(flag, vr, context)
  variation = vr.variation
  return variation, false unless variation.nil? # fixed variation
  rollout = vr.rollout
  return nil, false if rollout.nil?
  variations = rollout.variations
  if !variations.nil? && variations.length > 0 # percentage rollout
    rollout_is_experiment = rollout.is_experiment
    bucket_by = rollout_is_experiment ? nil : rollout.bucket_by
    bucket_by = 'key' if bucket_by.nil?

    seed = rollout.seed
    bucket = bucket_context(context, rollout.context_kind, flag.key, bucket_by, flag.salt, seed) # may not be present
    in_experiment = rollout_is_experiment && !bucket.nil?
    sum = 0
    variations.each do |variate|
      sum += variate.weight.to_f / 100000.0
      if bucket.nil? || bucket < sum
        return variate.variation, in_experiment && !variate.untracked
      end
    end
    # The context's bucket value was greater than or equal to the end of the last bucket. This could happen due
    # to a rounding error, or due to the fact that we are scaling to 100000 rather than 99999, or the flag
    # data could contain buckets that don't actually add up to 100000. Rather than returning an error in
    # this case (or changing the scaling, which would potentially change the results for *all* contexts), we
    # will simply put the context in the last bucket.
    last_variation = variations[-1]
    [last_variation.variation, in_experiment && !last_variation.untracked]
  else # the rule isn't well-formed
    [nil, false]
  end
end