helper thread checking filesystem resources

Question

I am running http server which serves requests constantly. I would like to have separate "helper" thread, checking if directory in filesystem is available. If the resource is gone, then I would like this helper thread to return value to main thread so I can stop the http server.

def main():
    os.chdir(root)
    server = HTTPServer(('0.0.0.0', 80), MyHandler)
    server.serve_forever()

I was thinking about sth like

def foo(bar, baz):
  print 'hello {0}'.format(bar)
  return 'foo' + baz

from multiprocessing.pool import ThreadPool
pool = ThreadPool(processes=1)

async_result = pool.apply_async(foo, ('world', 'foo')) # tuple of args for foo

# do some other stuff in the main process

return_val = async_result.get()  # get the return value from your function.

and stop the server if return_val == "stop"

Is it the best way of doing it?

Answer 1

if you're willing to drop the async stuff (because honestly i don't see your justification for needing it) you can just do

while foo():
    server.handle_request()

instead of server.serve_forever()

if you really want to do the check asynchronously you need to show a bit more code of how you intend to use it, do you want it to check constantly? once in a while? triggered by some event?

edit: you can still use a while loop just with the if inside

while True:
    if foo():
        server.handle_request()
    else:
        sleep(1) # or if foo is blocking (like when accessing the file system) you can just not sleep