Module: LaunchDarkly::Evaluation

Included in:
LDClient
Defined in:
lib/ldclient-rb/evaluation.rb

Defined Under Namespace

Classes: EvaluationError

Constant Summary collapse

BUILTINS = 
[:key, :ip, :country, :email, :firstName, :lastName, :avatar, :name, :anonymous]
NUMERIC_VERSION_COMPONENTS_REGEX = 
Regexp.new("^[0-9.]*")
DATE_OPERAND = 
lambda do |v|
  if v.is_a? String
    begin
      DateTime.rfc3339(v).strftime("%Q").to_i
    rescue => e
      nil
    end
  elsif v.is_a? Numeric
    v
  else
    nil
  end
end
SEMVER_OPERAND = 
lambda do |v|
  semver = nil
  if v.is_a? String
    for _ in 0..2 do
      begin
        semver = Semantic::Version.new(v)
        break  # Some versions of jruby cannot properly handle a return here and return from the method that calls this lambda
      rescue ArgumentError
        v = addZeroVersionComponent(v)
      end
    end
  end
  semver
end
OPERATORS = 
{
  in:
    lambda do |a, b|
      a == b
    end,
  endsWith:
    lambda do |a, b|
      (a.is_a? String) && (a.end_with? b)
    end,
  startsWith:
    lambda do |a, b|
      (a.is_a? String) && (a.start_with? b)
    end,
  matches:
    lambda do |a, b|
      (b.is_a? String) && !(Regexp.new b).match(a).nil?
    end,
  contains:
    lambda do |a, b|
      (a.is_a? String) && (a.include? b)
    end,
  lessThan:
    lambda do |a, b|
      (a.is_a? Numeric) && (a < b)
    end,
  lessThanOrEqual:
    lambda do |a, b|
      (a.is_a? Numeric) && (a <= b)
    end,
  greaterThan:
    lambda do |a, b|
      (a.is_a? Numeric) && (a > b)
    end,
  greaterThanOrEqual:
    lambda do |a, b|
      (a.is_a? Numeric) && (a >= b)
    end,
  before:
    comparator(DATE_OPERAND) { |n| n < 0 },
  after:
    comparator(DATE_OPERAND) { |n| n > 0 },
  semVerEqual:
    comparator(SEMVER_OPERAND) { |n| n == 0 },
  semVerLessThan:
    comparator(SEMVER_OPERAND) { |n| n < 0 },
  semVerGreaterThan:
    comparator(SEMVER_OPERAND) { |n| n > 0 },
  segmentMatch:
    lambda do |a, b|
      false   # we should never reach this - instead we special-case this operator in clause_match_user
    end
}

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.addZeroVersionComponent(v) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 39

def self.addZeroVersionComponent(v)
  NUMERIC_VERSION_COMPONENTS_REGEX.match(v) { |m|
    m[0] + ".0" + v[m[0].length..-1]
  }
end

.comparator(converter) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 45

def self.comparator(converter)
  lambda do |a, b|
    av = converter.call(a)
    bv = converter.call(b)
    if !av.nil? && !bv.nil?
      yield av <=> bv
    else
      return false
    end
  end
end

Instance Method Details

#bucket_user(user, key, bucket_by, salt) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 291

def bucket_user(user, key, bucket_by, salt)
  return nil unless user[:key]

  id_hash = bucketable_string_value(user_value(user, bucket_by))
  if id_hash.nil?
    return 0.0
  end

  if user[:secondary]
    id_hash += "." + user[:secondary]
  end

  hash_key = "%s.%s.%s" % [key, salt, id_hash]

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

#bucketable_string_value(value) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 309

def bucketable_string_value(value)
  return value if value.is_a? String
  return value.to_s if value.is_a? Integer
  nil
end

#clause_match_user(clause, user, store) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 213

def clause_match_user(clause, user, store)
  # In the case of a segment match operator, we check if the user is in any of the segments,
  # and possibly negate
  if clause[:op].to_sym == :segmentMatch
    (clause[:values] || []).each do |v|
      segment = store.get(SEGMENTS, v)
      return maybe_negate(clause, true) if !segment.nil? && segment_match_user(segment, user)
    end
    return maybe_negate(clause, false)
  end
  clause_match_user_no_segments(clause, user)
end

#clause_match_user_no_segments(clause, user) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 226

def clause_match_user_no_segments(clause, user)
  val = user_value(user, clause[:attribute])
  return false if val.nil?

  op = OPERATORS[clause[:op].to_sym]

  if op.nil?
    raise EvaluationError, "Unsupported operator #{clause[:op]} in evaluation"
  end

  if val.is_a? Enumerable
    val.each do |v|
      return maybe_negate(clause, true) if match_any(op, v, clause[:values])
    end
    return maybe_negate(clause, false)
  end

  maybe_negate(clause, match_any(op, val, clause[:values]))
end

#eval_internal(flag, user, store, events) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 142

def eval_internal(flag, user, store, events)
  failed_prereq = false
  # Evaluate prerequisites, if any
  (flag[:prerequisites] || []).each do |prerequisite|
    prereq_flag = store.get(FEATURES, prerequisite[:key])

    if prereq_flag.nil? || !prereq_flag[:on]
      failed_prereq = true
    else
      begin
        prereq_res = eval_internal(prereq_flag, user, store, events)
        variation = get_variation(prereq_flag, prerequisite[:variation])
        events.push(kind: "feature", key: prereq_flag[:key], value: prereq_res, version: prereq_flag[:version], prereqOf: flag[:key])
        if prereq_res.nil? || prereq_res != variation
          failed_prereq = true
        end
      rescue => exn
        @config.logger.error { "[LDClient] Error evaluating prerequisite: #{exn.inspect}" }
        failed_prereq = true
      end
    end
  end

  if failed_prereq
    return nil
  end
  # The prerequisites were satisfied.
  # Now walk through the evaluation steps and get the correct
  # variation index
  eval_rules(flag, user, store)
end

#eval_rules(flag, user, store) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 174

def eval_rules(flag, user, store)
  # Check user target matches
  (flag[:targets] || []).each do |target|
    (target[:values] || []).each do |value|
      return get_variation(flag, target[:variation]) if value == user[:key]
    end
  end

  # Check custom rules
  (flag[:rules] || []).each do |rule|
    return variation_for_user(rule, user, flag) if rule_match_user(rule, user, store)
  end

  # Check the fallthrough rule
  if !flag[:fallthrough].nil?
    return variation_for_user(flag[:fallthrough], user, flag)
  end

  # Not even the fallthrough matched-- return the off variation or default
  nil
end

#evaluate(flag, user, store) ⇒ Object

Evaluates a feature flag, returning a hash containing the evaluation result and any events generated during prerequisite evaluation. Raises EvaluationError if the flag is not well-formed Will return nil, but not raise an exception, indicating that the rules (including fallthrough) did not match In that case, the caller should return the default value.



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# File 'lib/ldclient-rb/evaluation.rb', line 117

def evaluate(flag, user, store)
  if flag.nil?
    raise EvaluationError, "Flag does not exist"
  end

  if user.nil? || user[:key].nil?
    raise EvaluationError, "Invalid user"
  end

  events = []

  if flag[:on]
    res = eval_internal(flag, user, store, events)

    return { value: res, events: events } if !res.nil?
  end

  if !flag[:offVariation].nil? && flag[:offVariation] < flag[:variations].length
    value = flag[:variations][flag[:offVariation]]
    return { value: value, events: events }
  end

  { value: nil, events: events }
end

#get_variation(flag, index) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 196

def get_variation(flag, index)
  if index >= flag[:variations].length
    raise EvaluationError, "Invalid variation index"
  end
  flag[:variations][index]
end

#match_any(op, value, values) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 331

def match_any(op, value, values)
  values.each do |v|
    return true if op.call(value, v)
  end
  return false
end

#maybe_negate(clause, b) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 327

def maybe_negate(clause, b)
  clause[:negate] ? !b : b
end

#rule_match_user(rule, user, store) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 203

def rule_match_user(rule, user, store)
  return false if !rule[:clauses]

  (rule[:clauses] || []).each do |clause|
    return false if !clause_match_user(clause, user, store)
  end

  return true
end

#segment_match_user(segment, user) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 264

def segment_match_user(segment, user)
  return false unless user[:key]

  return true if segment[:included].include?(user[:key])
  return false if segment[:excluded].include?(user[:key])

  (segment[:rules] || []).each do |r|
    return true if segment_rule_match_user(r, user, segment[:key], segment[:salt])
  end

  return false
end

#segment_rule_match_user(rule, user, segment_key, salt) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 277

def segment_rule_match_user(rule, user, segment_key, salt)
  (rule[:clauses] || []).each do |c|
    return false unless clause_match_user_no_segments(c, user)
  end

  # If the weight is absent, this rule matches
  return true if !rule[:weight]
  
  # All of the clauses are met. See if the user buckets in
  bucket = bucket_user(user, segment_key, rule[:bucketBy].nil? ? "key" : rule[:bucketBy], salt)
  weight = rule[:weight].to_f / 100000.0
  return bucket < weight
end

#user_value(user, attribute) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 315

def user_value(user, attribute)
  attribute = attribute.to_sym

  if BUILTINS.include? attribute
    user[attribute]
  elsif !user[:custom].nil?
    user[:custom][attribute]
  else
    nil
  end
end

#variation_for_user(rule, user, flag) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 246

def variation_for_user(rule, user, flag)
  if !rule[:variation].nil? # fixed variation
    return get_variation(flag, rule[:variation])
  elsif !rule[:rollout].nil? # percentage rollout
    rollout = rule[:rollout]
    bucket_by = rollout[:bucketBy].nil? ? "key" : rollout[:bucketBy]
    bucket = bucket_user(user, flag[:key], bucket_by, flag[:salt])
    sum = 0;
    rollout[:variations].each do |variate|
      sum += variate[:weight].to_f / 100000.0
      return get_variation(flag, variate[:variation]) if bucket < sum
    end
    nil
  else # the rule isn't well-formed
    raise EvaluationError, "Rule does not define a variation or rollout"
  end
end