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# Copyright (C) 2014-2017 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
module ServerSelector
# Encapsulates specifications for selecting near servers given a list
# of candidates.
#
# @since 2.0.0
class Nearest
include Selectable
# Name of the this read preference in the server's format.
#
# @since 2.5.0
SERVER_FORMATTED_NAME = 'nearest'.freeze
# Get the name of the server mode type.
#
# @example Get the name of the server mode for this preference.
# preference.name
#
# @return [ Symbol ] :nearest
#
# @since 2.0.0
def name
:nearest
end
# Whether the slaveOk bit should be set on wire protocol messages.
# I.e. whether the operation can be performed on a secondary server.
#
# @return [ true ] true
#
# @since 2.0.0
def slave_ok?
true
end
# Whether tag sets are allowed to be defined for this server preference.
#
# @return [ true ] true
#
# @since 2.0.0
def tags_allowed?
true
end
# Convert this server preference definition into a format appropriate
# for a mongos server.
#
# @example Convert this server preference definition into a format
# for mongos.
# preference = Mongo::ServerSelector::Nearest.new
# preference.to_mongos
#
# @return [ Hash ] The server preference formatted for a mongos server.
#
# @since 2.0.0
def to_mongos
@doc ||= (preference = { :mode => SERVER_FORMATTED_NAME }
preference.merge!({ :tags => tag_sets }) unless tag_sets.empty?
preference.merge!({ maxStalenessSeconds: max_staleness }) if max_staleness
preference)
end
alias :to_doc :to_mongos
private
# Select the near servers taking into account any defined tag sets and
# local threshold between the nearest server and other servers.
#
# @example Select nearest servers given a list of candidates.
# preference = Mongo::ServerSelector::Nearest.new
# preference.select_server(cluster)
#
# @return [ Array ] The nearest servers from the list of candidates.
#
# @since 2.0.0
def select(candidates)
matching_servers = filter_stale_servers(candidates, primary(candidates).first)
matching_servers = match_tag_sets(matching_servers) unless tag_sets.empty?
near_servers(matching_servers)
end
def max_staleness_allowed?
true
end
end
end
end
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