Class: Celluloid::Presence::ZkPresence

Inherits:
Object
  • Object
show all
Includes:
Celluloid, Notifications
Defined in:
lib/celluloid-presence/presence.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ ZkPresence

Returns a new instance of ZkPresence.



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# File 'lib/celluloid-presence/presence.rb', line 18

def initialize(options = {})
	@env = options[:env] || 'production'
	@base_path = options[:service_name].nil? ? "#{PREFIX}/#{@env}/default" : "#{PREFIX}/#{@env}/#{options[:service_name]}"
	@base_path_sym = @base_path.to_sym
	@node_path = nil	# This is officially set in connect_setup
	@service_name = options[:service_name] || :default
	@nodes = []
		
	if options[:node_address].nil?
		use_ip_v4 = !options[:ip_v6]		# IP v6 or IP v4 if using the default node data
		@node_address = proc { ip_address(use_ip_v4) }
	else
		node_address = options[:node_address]
		@node_address = proc { node_address.is_a?(Proc) ? node_address.call : node_address }
	end
	@last_known_address = nil
		
	#
	# These callbacks will be executed on a seperate thread
	# Which is why we need to use notifications update state
	#
	zk.register(@base_path)
	subscribe("zk_event_#{@base_path}", :zk_callback)
	subscribe('zk_connected', :on_connected)
	subscribe('zk_connecting', :on_connecting)
	
	on_connected
end

Instance Attribute Details

#nodes ⇒ Object (readonly)

Provides the list of known nodes



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# File 'lib/celluloid-presence/presence.rb', line 51

def nodes
  @nodes
end

Class Method Details

.finalizer ⇒ Object 



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# File 'lib/celluloid-presence/presence.rb', line 13

def self.finalizer
	:finalize
end

Instance Method Details

#get(node_id) ⇒ Object

Returns the value of a node



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# File 'lib/celluloid-presence/presence.rb', line 102

def get(node_id)
	result, _ = zk.get("#{@base_path}/#{node_id}")
	result
rescue ZK::Exceptions::NoNode
end

#name ⇒ Object

Returns the name of this node



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# File 'lib/celluloid-presence/presence.rb', line 111

def name
	@node_path.split('/')[-1]
end

#on_connected(event = nil) ⇒ Object

This informs us of a new connection being established with zookeeper



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# File 'lib/celluloid-presence/presence.rb', line 72

def on_connected(event = nil)
	return unless zk.connected?
	
	address = @node_address.call
	if @node_path.nil? or not zk.exists?(@node_path)	# Create presence node as it doesn't exist
		#p 'node re-created'
		@last_known_address = address
		connect_setup
	elsif @last_known_address != address		# Recreate existing presence node as our IP changed
		#p 'node ip_changed, recreating'
		zk.async.ensure(:delete, @node_path)
		@last_known_address = address
		connect_setup
	else												# Else our node presence information is accurate, lets get the latest list
		@nodes = zk.children(@base_path, :watch => true)
	end
	
	update_node_information								# inform listeners of a node list update
end

#on_connecting(event) ⇒ Object

This informs us that we’ve been disconnected from zookeeper



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# File 'lib/celluloid-presence/presence.rb', line 95

def on_connecting event
	publish("#{@service_name}_nodes_stale")
end

#zk_callback(event_name, event) ⇒ Object

This informs us of changes to the list of base path’s children



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# File 'lib/celluloid-presence/presence.rb', line 57

def zk_callback(event_name, event)
	#p "EVENT OCUURED #{event.event_name} #{event.path}"
	if event.node_child?	# We are only listening to child events so we only need to handle these
		begin
			@nodes = zk.children(@base_path, :watch => true)    # re-set watch
			update_node_information
		rescue ZK::Exceptions::NoNode		# Technically this shouldn't happen unless someone deleted our base path
			on_connected
		end
	end
end