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module RedisFailover
# Provides manual failover support to a new master.
class ManualFailover
# Path for manual failover communication.
ZNODE_PATH = 'manual_failover'.freeze
# Denotes that any slave can be used as a candidate for promotion.
ANY_SLAVE = "ANY_SLAVE".freeze
def self.path(root_znode)
"#{root_znode}/#{ZNODE_PATH}"
end
# Creates a new instance.
#
# @param [ZK] zk the ZooKeeper client
# @param [ZNode] root_znode the root ZK node
# @param [Hash] options the options used for manual failover
# @option options [String] :host the host of the failover candidate
# @option options [String] :port the port of the failover candidate
# @note
# If options is empty, a random slave will be used
# as a failover candidate.
def initialize(zk, root_znode, options = {})
@zk = zk
@root_znode = root_znode
@options = options
unless @options.empty?
port = Integer(@options[:port]) rescue nil
raise ArgumentError, ':host not properly specified' if @options[:host].to_s.empty?
raise ArgumentError, ':port not properly specified' if port.nil?
end
end
# Performs a manual failover.
def perform
create_path
node = @options.empty? ? ANY_SLAVE : "#{@options[:host]}:#{@options[:port]}"
@zk.set(self.class.path(@root_znode), node)
end
private
# Creates the znode path used for coordinating manual failovers.
def create_path
@zk.create(self.class.path(@root_znode))
rescue ZK::Exceptions::NodeExists
# best effort
end
end
end
Version data entries
13 entries across 13 versions & 3 rubygems