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]
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:
    lambda do |a, b|
      begin
        if a.is_a? String
          a = DateTime.rfc3339(a).strftime('%Q').to_i 
        end
        if b.is_a? String
          b = DateTime.rfc3339(b).strftime('%Q').to_i
        end          
        (a.is_a? Numeric) ? a < b : false
      rescue => e
        false
      end
    end,
  after:
    lambda do |a, b|
      begin
        if a.is_a? String
          a = DateTime.rfc3339(a).strftime('%Q').to_i 
        end
        if b.is_a? String
          b = DateTime.rfc3339(b).strftime('%Q').to_i 
        end          
        (a.is_a? Numeric) ? a > b : false
      rescue => e
        false
      end
    end
}

Instance Method Summary collapse

Instance Method Details

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



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# File 'lib/ldclient-rb/evaluation.rb', line 225

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

  id_hash = user_value(user, bucket_by)

  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

#clause_match_user(clause, user) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 187

def clause_match_user(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 107

def eval_internal(flag, user, store, events)
  failed_prereq = false
  # Evaluate prerequisites, if any
  if !flag[:prerequisites].nil?
    flag[:prerequisites].each do |prerequisite|

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

#eval_rules(flag, user) ⇒ Object 



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

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

  # Check custom rules
  if !flag[:rules].nil?
    flag[:rules].each do |rule|
      return variation_for_user(rule, user, flag) if rule_match_user(rule, user)
    end
  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 82

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 170

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 256

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 252

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

#rule_match_user(rule, user) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 177

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

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

  return true
end

#user_value(user, attribute) ⇒ Object 



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# File 'lib/ldclient-rb/evaluation.rb', line 240

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 207

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