CherryPy waits for extra thread to end that is stopped later

Question

I am building a application that uses CherryPy to serve a REST API, and another thread that does background work (in fact, it reads data from a serial port).

import cherrypy
import threading

class main:
    @cherrypy.expose
    def index(self):
        return "Hello World."

def run():
   while running == True:
       # read data from serial port and store in a variable

running = True
t = threading.Thread(target = run)
t.start()

if __name__ == '__main__':
    cherrypy.quickstart(main())

running = False

Both api.pc_main() and run work fine. The trouble is, I use a running boolean to stop my thread, but that piece of code is never reached, because CherryPy waits for that thread to finish when I push Ctrl-C. I actually have to use kill -9 to stop the process.

global variables are always a bad idea because of such cases — Azat Ibrakov, Apr 29 '17 at 14:44
@AzatIbrakov that is just to make the example. The actual code uses a class that has the `running` boolean. — Bart Friederichs, Apr 29 '17 at 14:45
it doesn't change anything, you just moving variable from global scope to class scope — Azat Ibrakov, Apr 29 '17 at 14:46
@AzatIbrakov well, it does change something. It isn't global anymore. Not to mention, it is not the point of my question. — Bart Friederichs, Apr 29 '17 at 14:47
@AzatIbrakov no. The serial port will have a continuous stream of data coming, that I need to read. — Bart Friederichs, Apr 29 '17 at 14:48
can you use `Python 3` instead? it has a nice `asyncio` lib for solving such problems — Azat Ibrakov, Apr 29 '17 at 14:50
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/142968/discussion-between-bart-friederichs-and-azat-ibrakov). — Bart Friederichs, Apr 29 '17 at 14:52

score 2 · Accepted Answer · edited May 23 '17 at 12:34

I fixed it by making my thread a CherryPy plugin. I used the code found here: Why is CTRL-C not captured and signal_handler called?

from cherrypy.process.plugins import SimplePlugin

class myplugin(SimplePlugin):
    running = False
    thread = None

    def __init__(self, bus):
        SimplePlugin.__init__(self, bus)

    def start(self):
        print "Starting thread."
        self.running = True
        if not self.thread:
            self.thread = threading.Thread(target = self.run)
            self.thread.start()

    def stop(self):
        print "Stopping thread."
        self.running = False

        if self.thread:
            self.thread.join()
            self.thread = None


    def run(self):
        while self.running == True:
            print "Thread runs."
            time.sleep(1)

then in the main script:

if __name__ == '__main__':
    mythread(cherrypy.engine).subscribe()
    cherrypy.quickstart(main())

CherryPy waits for extra thread to end that is stopped later

1 Answers1