`class Socket`

Implements the systemd NOTIFY_SOCKET process readiness protocol. See https://www.freedesktop.org/software/systemd/man/sd_notify.html for more details of the underlying protocol.

Definitions

`NOTIFY_SOCKET = 'NOTIFY_SOCKET'`

The name of the environment variable which contains the path to the notification socket.

`MAXIMUM_MESSAGE_SIZE = 4096`

The maximum allowed size of the UDP message.

`def self.open!(environment = ENV)`

Open a notification client attached to the current NOTIFY_SOCKET = 'NOTIFY_SOCKET' if possible.

Implementation

def self.open!(environment = ENV)
	if path = environment.delete(NOTIFY_SOCKET)
		self.new(path)
	end
end

`def initialize(path)`

Initialize the notification client.

Signature

parameter　path　String: The path to the UNIX socket used for sending messages to the process manager.

Implementation

def initialize(path)
	@path = path
	@endpoint = IO::Endpoint.unix(path, ::Socket::SOCK_DGRAM)
end

`def dump(message)`

Dump a message in the format requied by sd_notify.

Signature

parameter　message　Hash: Keys and values should be string convertible objects. Values which are true/false are converted to 1/0 respectively.

Implementation

def dump(message)
	buffer = String.new
	
	message.each do |key, value|
		# Conversions required by NOTIFY_SOCKET specifications:
		if value == true
			value = 1
		elsif value == false
			value = 0
		end
		
		buffer << "#{key.to_s.upcase}=#{value}\n"
	end
	
	return buffer
end

`def send(**message)`

Send the given message.

Signature

parameter　message　Hash

Implementation

def send(**message)
	data = dump(message)
	
	if data.bytesize > MAXIMUM_MESSAGE_SIZE
		raise ArgumentError, "Message length #{message.bytesize} exceeds #{MAXIMUM_MESSAGE_SIZE}: #{message.inspect}"
	end
	
	Sync do
		@endpoint.connect do |peer|
			peer.send(data)
		end
	end
end

`def error!(text, **message)`

Send the specified error. sd_notify requires an errno key, which defaults to -1 to indicate a generic error.

Implementation

def error!(text, **message)
	message[:errno] ||= -1
	
	send(status: text, **message)
end