[Python] Service with named unix socket controller

延續上次 [Python] Create thread, and receive signal to handle reload, shutdown 的需求，建立一個service，但這次不收signal, 而是改用socket接受reload和stop命令。

幾個重點：
1. 不會因為接收signal而中斷IO
2. 需要建立一個controller (client) 來對service發送指令
3. controller會等service確實執行完動作才退出，不像kill丟了signal就跑。
所以service在應該確保每次check socket之間不超過一定時間，萬一對controller下reload的另一端，有來自front end(UI)的request在等，request可能遇到timeout而被中斷。
4. 建立無檔案socket address，不用建檔砍檔也不用管檔案權限，但是只有Linux可用，MacOSx試過不行....

	#!/usr/bin/env python
	# encoding: utf-8
	'''
	usage:
	python testNamedSocketClieht.py reload
	python testNamedSocketClieht.py stop
	'''
	import socket
	import sys
	import time
	server_address = '\x00testNamedSocket'
	if len(sys.argv) == 2:
	act = str(sys.argv[1]).lower()
	if act in ['stop', 'reload']:
	sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
	print 'connecting to %s' % server_address
	try:
	sock.connect(server_address)
	except socket.error, msg:
	print msg
	sys.exit(1)
	try:
	print 'sending "%s"' % act
	sock.sendall(act)
	amount_received = 0
	amount_expected = len(act)
	while amount_received < amount_expected:
	data = sock.recv(16)
	amount_received += len(data)
	print 'received "%s"' % data
	time.sleep(1)
	finally:
	print 'closing socket'
	sock.close()
	else:
	print "Unknown command"
	sys.exit(2)
	sys.exit(0)
	else:
	print "usage: %s stop|reload" % sys.argv[0]
	sys.exit(2)

view raw testNamedSocketClient.py hosted with ❤ by GitHub

	#!/usr/bin/env python
	# encoding: utf-8
	import time
	import socket
	import errno
	'''
	Put null character at beginning to open a
	"Named Unix Socket", without opening file system path.
	Only supported by Linux, not by Mac OSX.
	'''
	server_address = '\x00testNamedSocket'
	class TestService():
	sock = None
	connection = None
	def __init__(self):
	print 'init'
	self.sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
	self.sock.bind(server_address)
	self.sock.setblocking(0)
	# 1 for only keep 1 message queued on buffer.
	self.sock.listen(1)
	def __del__ (self) :
	print 'del'
	if self.connection:
	self.connection.close()
	def delay_reload(self):
	print 'reloading'
	cnt = 5
	while cnt > 0:
	print '.'
	cnt -= 1
	time.sleep(1)
	def delay_stop(self):
	print 'stopping'
	cnt = 10
	while cnt > 0:
	print '.'
	cnt -= 1
	time.sleep(1)
	def check_socket(self):
	try:
	#sock.setblocking(0) will raise error 11 here.
	self.connection, client_address = self.sock.accept()
	print 'connection from %s' % client_address
	data = self.connection.recv(16)
	if not data:
	print 'no data from %s' % client_address
	return None
	print 'received "%s"' % data
	act = str(data).lower()
	if act in ['stop', 'reload']:
	return act
	else:
	#echo unsupported acts immediately
	self.connection.sendall(data)
	except socket.error, e:
	if errno.EAGAIN == e.errno:
	return None
	else:
	raise e
	return None
	def run(self):
	while True:
	print '-'
	act = self.check_socket()
	if 'reload' == act:
	self.delay_reload()
	self.connection.sendall(act)
	elif 'stop' == act:
	self.delay_stop()
	self.connection.sendall(act)
	break
	else:
	pass
	time.sleep(2)
	if __name__ == '__main__':
	mainThread = TestService()
	mainThread.run()

view raw testNamedSocketServer.py hosted with ❤ by GitHub