Multiprocess Support

[sknepal]

Hi, does Terminado somehow mess with the multiprocess support provided by Tornado? I'm getting RuntimeError: Cannot run in multiple processes: IOLoop instance has already been initialized. You cannot call IOLoop.instance() before calling start_processes() error while trying to implement multiprocess as shown here. It works fine with single process.

What gave the above error is this:

import tornado.web
from tornado.ioloop import IOLoop
from terminado import TermSocket, UniqueTermManager
import tornado.httpserver

if __name__ == '__main__':
    term_manager = UniqueTermManager(shell_command=["rbash"])
    handlers = [
                (r"/websocket", TermSocket, {'term_manager': term_manager}),
                (r"/()", tornado.web.StaticFileHandler, {'path':'index.html'}),
                (r"/(.*)", tornado.web.StaticFileHandler, {'path':'.'}),
               ]
    try:
        app = tornado.web.Application(handlers,debug=False,autoreload=False)
        server = tornado.httpserver.HTTPServer(app)
        server.bind(8079)
	server.start(0)
        IOLoop.current().start()
    finally:
        term_manager.shutdown()

Can you please provide an example usage of Terminado with Multiprocess and/or Multithread support? Thank you!

[takluyver]

I had no idea that tornado had specific multiprocess support. The manager object needs a reference to the IOLoop, so instantiating that gets the current IOLoop, which appears to be what causes the problem.

Looking at those docs, I think you should be able to use the 'advanced multi-process' interface it describes.

[sknepal]

@takluyver I did try the sample code of the 'advanced multi-process' mentioned there, but it also resulted in the same error. Do you think I need to make any changes to it (specifically for Terminado's case) ? Can you please look into supporting it? Thank you.

[takluyver]

I suspect you'll need to call fork_processes() before you create term_manager.

[sknepal]

Thank you it does not show the error now.

But, I am having another issue. I am using Terminado as a backend for xtermjs to make terminal accessible on the web. Instead of directly running rbash, I am using a jailed terminal by using firejail (i.e. term_manager = UniqueTermManager(shell_command=["firejail","rbash"]). The problem is, firejail does not exit when the client closes the tab/window. It does not appear as a zombie process either, its pretty much active. Can you please point me to the write direction?

Edit: Seems like its a Firejail issue. I'll put the question there; but if you have a solution to handle it via Terminado, please share. Thanks!