failover.rb

module Flipper
  module Adapters
    class Failover
      include ::Flipper::Adapter

      # Public: Build a new failover instance.
      #
      # primary   - The primary flipper adapter.
      # secondary - The secondary flipper adapter which services reads when
      #             the primary adapter is unavailable.
      # options   - Hash of options:
      #             :dual_write - Boolean, whether to update secondary when
      #                           primary is updated
      #             :errors - Array of exception types for which to failover

      attr_reader :primary, :secondary

      def initialize(primary, secondary, options = {})
        @primary = primary
        @secondary = secondary

        @dual_write = options.fetch(:dual_write, false)
        @errors = options.fetch(:errors, [ StandardError ])
      end

      def adapter_stack
        "#{name}(primary: #{@primary.adapter_stack}, secondary: #{@secondary.adapter_stack})"
      end

      def features
        @primary.features
      rescue *@errors
        @secondary.features
      end

      def get(feature)
        @primary.get(feature)
      rescue *@errors
        @secondary.get(feature)
      end

      def get_multi(features)
        @primary.get_multi(features)
      rescue *@errors
        @secondary.get_multi(features)
      end

      def get_all(**kwargs)
        @primary.get_all(**kwargs)
      rescue *@errors
        @secondary.get_all(**kwargs)
      end

      def add(feature)
        @primary.add(feature).tap do
          @secondary.add(feature) if @dual_write
        end
      end

      def remove(feature)
        @primary.remove(feature).tap do
          @secondary.remove(feature) if @dual_write
        end
      end

      def clear(feature)
        @primary.clear(feature).tap do
          @secondary.clear(feature) if @dual_write
        end
      end

      def enable(feature, gate, thing)
        @primary.enable(feature, gate, thing).tap do
          @secondary.enable(feature, gate, thing) if @dual_write
        end
      end

      def disable(feature, gate, thing)
        @primary.disable(feature, gate, thing).tap do
          @secondary.disable(feature, gate, thing) if @dual_write
        end
      end

      def read_integer(key)
        @primary.read_integer(key)
      rescue *@errors
        @secondary.read_integer(key)
      end

      def set_integer_if_greater(key, value)
        accepted = @primary.set_integer_if_greater(key, value)
        @secondary.set_integer_if_greater(key, value) if accepted && @dual_write
        accepted
      end
    end
  end
end