async-process.py

# Copyright (c) 2010, Philip Plante of EndlessPaths.com
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

import logging
import shlex
import subprocess
import tornado.web
import tornado.ioloop
import tornado.httpclient

class AsyncProcessMixIn(tornado.web.RequestHandler):
	def call_subprocess(self, command, callback=None):
		self.ioloop = tornado.ioloop.IOLoop.instance()
		self.pipe = p = subprocess.Popen(shlex.split(command), 
			stdin=subprocess.PIPE, 
			stdout=subprocess.PIPE, 
			stderr=subprocess.PIPE, 
			close_fds=True)
		self.ioloop.add_handler(p.stdout.fileno(), 
			self.async_callback(self.on_subprocess_result, callback), 
			self.ioloop.READ)

	def on_subprocess_result(self, callback, fd, result):
		try:
			if callback:
				callback(self.pipe.stdout, self.pipe.stderr)
		except Exception, e:
			logging.error(e)
		finally:
			self.ioloop.remove_handler(fd)

class SampleHandler(AsyncProcessMixIn):
	@tornado.web.asynchronous
	def get(self):
		self.call_subprocess('ls /', self.on_ls)
	
	def on_ls(self, out, err):
		self.write("stdout is:\n%s" % (out.read(),))
		self.write("stderr is:\n%s" % (err.read(),))
		self.finish()

application = tornado.web.Application([
    (r"/", SampleHandler),
])

if __name__ == "__main__":
    application.listen(8888)
    tornado.ioloop.IOLoop.instance().start()