features.rb

# frozen_string_literal: true
# rubocop:todo all

# Copyright (C) 2014-2020 MongoDB Inc.
#
# Licensed under the Apache License, Version 2.0 (the 'License');
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an 'AS IS' BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

module Mongo
  class Server
    class Description

      # Defines behavior around what features a specific server supports.
      #
      # @since 2.0.0
      class Features
        # List of features and the wire protocol version they appear in.
        #
        # Wire protocol versions map to server releases as follows:
        # -  2 => 2.6
        # -  3 => 3.0
        # -  4 => 3.2
        # -  5 => 3.4
        # -  6 => 3.6
        # -  7 => 4.0
        # -  8 => 4.2
        # -  9 => 4.4
        # - 13 => 5.0
        # - 14 => 5.1
        # - 17 => 6.0
        #
        # @since 2.0.0
        MAPPINGS = {
          merge_out_on_secondary: 13,
          get_more_comment: 9,
          retryable_write_error_label: 9,
          commit_quorum: 9,
          # Server versions older than 4.2 do not reliably validate options
          # provided by the client during findAndModify operations, requiring the
          # driver to raise client-side errors when those options are provided.
          find_and_modify_option_validation: 8,
          sharded_transactions: 8,
          transactions: 7,
          scram_sha_256: 7,
          array_filters: 6,
          op_msg: 6,
          sessions: 6,
          collation: 5,
          max_staleness: 5,
          # Server versions older than 3.4 do not reliably validate options
          # provided by the client during update/delete operations, requiring the
          # driver to raise client-side errors when those options are provided.
          update_delete_option_validation: 5,
          find_command: 4,
          list_collections: 3,
          list_indexes: 3,
          scram_sha_1: 3,
          write_command: 2,
          users_info: 2,
        }.freeze

        # Error message if the server is too old for this version of the driver.
        #
        # @since 2.5.0
        SERVER_TOO_OLD = "Server at (%s) reports wire version (%s), but this version of the Ruby driver " +
                           "requires at least (%s)."

        # Error message if the driver is too old for the version of the server.
        #
        # @since 2.5.0
        DRIVER_TOO_OLD = "Server at (%s) requires wire version (%s), but this version of the Ruby driver " +
                           "only supports up to (%s)."

        # The wire protocol versions that this version of the driver supports.
        #
        # @since 2.0.0
        DRIVER_WIRE_VERSIONS = (6..21).freeze

        # Create the methods for each mapping to tell if they are supported.
        #
        # @since 2.0.0
        MAPPINGS.each do |name, version|
          # Determine whether or not the feature is supported.
          #
          # @example Is a feature enabled?
          #   features.list_collections_enabled?
          #
          # @return [ true, false ] Whether the feature is supported.
          #
          # @since 2.0.0
          define_method("#{name}_enabled?") do
            server_wire_versions.include?(MAPPINGS[name])
          end
        end

        # @return [ Range ] server_wire_versions The server's supported wire
        #   versions.
        attr_reader :server_wire_versions

        # Initialize the features.
        #
        # @example Initialize the features.
        #   Features.new(0..3)
        #
        # @param [ Range ] server_wire_versions The server supported wire
        #   versions.
        #
        # @since 2.0.0
        def initialize(server_wire_versions, address = nil)
          if server_wire_versions.min.nil?
            raise ArgumentError, "server_wire_versions's min is nil"
          end
          if server_wire_versions.max.nil?
            raise ArgumentError, "server_wire_versions's max is nil"
          end
          @server_wire_versions = server_wire_versions
          @address = address

          if Mongo::Lint.enabled?
            freeze
          end
        end

        # Check that there is an overlap between the driver supported wire
        #   version range and the server wire version range.
        #
        # @example Verify the wire version overlap.
        #   features.check_driver_support!
        #
        # @raise [ Error::UnsupportedFeatures ] If the wire version range is
        #   not covered by the driver.
        #
        # @since 2.5.1
        def check_driver_support!
          if DRIVER_WIRE_VERSIONS.min > @server_wire_versions.max
            raise Error::UnsupportedFeatures.new(SERVER_TOO_OLD % [@address,
                                                                   @server_wire_versions.max,
                                                                   DRIVER_WIRE_VERSIONS.min])
          elsif DRIVER_WIRE_VERSIONS.max < @server_wire_versions.min
            raise Error::UnsupportedFeatures.new(DRIVER_TOO_OLD % [@address,
                                                                   @server_wire_versions.min,
                                                                   DRIVER_WIRE_VERSIONS.max])
          end
        end
      end
    end
  end
end