Class: Datadog::OpenFeature::EvaluationEngine

Inherits:
Object
  • Object
show all
Defined in:
lib/datadog/open_feature/evaluation_engine.rb

Overview

This class performs the evaluation of the feature flag

Constant Summary collapse

ReconfigurationError =

Steep: https://github.com/soutaro/steep/issues/1880

Class.new(StandardError)
ALLOWED_TYPES = 
%i[boolean string number float integer object].freeze

Instance Method Summary collapse

Constructor Details

#initialize(reporter, telemetry:, logger:) ⇒ EvaluationEngine

Returns a new instance of EvaluationEngine.



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# File 'lib/datadog/open_feature/evaluation_engine.rb', line 17

def initialize(reporter, telemetry:, logger:)
  @reporter = reporter
  @telemetry = telemetry
  @logger = logger

  @evaluator = NoopEvaluator.new(nil)
end

Instance Method Details

#fetch_value(flag_key, default_value:, expected_type:, evaluation_context: nil) ⇒ Object 



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# File 'lib/datadog/open_feature/evaluation_engine.rb', line 25

def fetch_value(flag_key, default_value:, expected_type:, evaluation_context: nil)
  # Pre-bound to the safe default so the rescue below can still read it if the
  # evaluator read itself raises.
  observe_full_evaluation_data = false
  # Snapshot the evaluator once: a concurrent reconfigure! must not retroactively
  # apply a different environment's full-evaluation-data policy to this evaluation.
  evaluator = @evaluator
  observe_full_evaluation_data = evaluator.observe_full_evaluation_data == true

  unless ALLOWED_TYPES.include?(expected_type)
    message = "unknown type #{expected_type.inspect}, allowed types #{ALLOWED_TYPES.join(", ")}"
    result = ResolutionDetails.build_error(
      value: default_value, error_code: Ext::UNKNOWN_TYPE, error_message: message
    )

    return with_observe_full_evaluation_data(result, observe_full_evaluation_data)
  end

  context = evaluation_context&.fields.to_h
  result = evaluator.get_assignment(
    flag_key, default_value: default_value, context: context, expected_type: expected_type
  )

  result = with_observe_full_evaluation_data(result, observe_full_evaluation_data)

  @reporter.report(result, flag_key: flag_key, context: evaluation_context)

  result
rescue => e
  @telemetry.report(e, description: "OpenFeature: Failed to fetch flag value")

  result = ResolutionDetails.build_error(
    value: default_value, error_code: Ext::GENERAL, error_message: "#{e.class}: #{e.message}"
  )
  # `== true` is load-bearing: Steep types this local as `(nil | bool)` in a rescue
  # body, and coercing at the use site is what narrows it to `bool`.
  with_observe_full_evaluation_data(result, observe_full_evaluation_data == true)
end

#reconfigure!(configuration) ⇒ Object

NOTE: In a currect implementation configuration is expected to be a raw JSON string containing feature flags (straight from the remote config) in the format expected by libdatadog without any modifications



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# File 'lib/datadog/open_feature/evaluation_engine.rb', line 67

def reconfigure!(configuration)
  if configuration.nil?
    @logger.debug("OpenFeature: Removing configuration")

    return @evaluator = NoopEvaluator.new(configuration)
  end

  @evaluator = NativeEvaluator.new(configuration)
rescue => e
  message = "OpenFeature: Failed to reconfigure, reverting to the previous configuration"

  @logger.error("#{message}, #{e.class}: #{e.message}")
  @telemetry.report(e, description: "#{message} (#{e.class})")

  raise ReconfigurationError, "#{e.class}: #{e.message}"
end