On 22/02/2015, at 5:33 AM, Paul Royik <[email protected]> wrote:
> From time to time I've got following error:
> [Sat Feb 21 12:24:27.181049 2015] [wsgi:info] [pid 5482:tid 139829356984064]
> [remote 127.0.0.1:12680] mod_wsgi (pid=5482): Force restart of process
> 'localhost:20241'.
>
> Is it normal?
That means that the WSGI script file for your application was modified. This is
detected and the mod_wsgi daemon process restarted automatically.
This is another reason why you shouldn't be doing stuff under web application
processes.
When this occurs, if you had an algorithm worker process running at the time,
the killing off of the daemon process running your web application may not
result in the worker being killed and so it could keep running with nothing
then killing it.
Will have to check that though, as depends on whether when daemon process is
killed that children also killed automatically.
How do you upload code changes to your system? Are you just using ssh to copy
your whole code base every time and so the WSGI script file modification time
will be updated even if not changed?
Graham
> On Saturday, February 21, 2015 at 3:14:16 PM UTC+2, Paul Royik wrote:
> Thank you very much.
> It works now.
> But I noticed one thing. When calculator works, memory jumps from 180 to 250
> (and the back to 180 as expected). When I used thread method, I didn't see
> such big jump. Can you tell me why in this case the jump is so big? I guess,
> that if 10 people will do it simulaneously, then I will run out of memory.
>
> Anyway, this is the cleanest and best solution.
>
>
> On Saturday, February 21, 2015 at 2:26:40 PM UTC+2, Graham Dumpleton wrote:
> The short answer is that code will not work with the version of mod_wsgi you
> are using. It will not kill the forked process properly and would actually
> kill the WSGI application daemon process instead, leaving the forked process
> still running and thus why it consumed memory. That it was killing the WSGI
> application daemon process would have been evident in the error logs which is
> why I asked about logs.
>
> Some extra tricks were required with a special directive needing to be given
> to mod_wsgi for the version you are using to allow signal handlers to be
> overridden and the forked process would need to reset the signal handlers
> before running the job.
>
> Since it was a pain to have to use the fiddles I worked out a way in mod_wsgi
> to avoid needing to do all that. You will need to upgrade to the latest
> mod_wsgi version though, which is 4.4.9.
>
> That isn't all that is required though as that code doesn't properly wait on
> the process when terminating it. This will result in a zombie process hanging
> around, which isn't a good idea. In worst case, since terminate() only tries
> SIGTERM, it may not go away.
>
> Now you can't simply go run 'pip install -U mod_wsgi' because of the issue we
> had with that breaking the mod_wsgi-httpd install. That issue has also now
> been fixed though. What you therefore want to do is reinstall both
> mod_wsgi-httpd and mod_wsgi.
>
> So if I got it right, you should be able to do.
>
> pip2.7 -v -v -v --log $HOME/pip.log install -U --user --build $HOME/tmp/pip
> mod_wsgi-httpd
> pip2.7 install -U --user mod_wsgi
>
> I am hoping that doesn't effect your running site. To be safe you may want to
> shut it down when doing the update.
>
> Once upgraded, use the following code. Remove print statements when happy. I
> would get rid of the force_kill flag as you probably always want to be force
> killing it and escalating that to SIGKILL to definitely get rid of it.
>
> import multiprocessing
> import signal
> import time
> import os
>
> class TimeoutException(Exception):
> pass
>
> class RunableProcessing(multiprocessing.Process):
> def __init__(self, func, *args, **kwargs):
> self.queue = multiprocessing.Queue(maxsize=1)
> args = (func,) + args
> multiprocessing.Process.__init__(self, target=self.run_func,
> args=args, kwargs=kwargs)
>
> def run_func(self, func, *args, **kwargs):
> try:
> result = func(*args, **kwargs)
> self.queue.put((True, result))
> except Exception as e:
> self.queue.put((False, e))
>
> def done(self):
> return self.queue.full()
>
> def result(self):
> return self.queue.get()
>
> def timeout(seconds, force_kill=True):
> def wrapper(function):
> def inner(*args, **kwargs):
> now = time.time()
> proc = RunableProcessing(function, *args, **kwargs)
> proc.start()
> proc.join(seconds)
> if proc.is_alive():
> print 'still alive'
> if force_kill:
> print 'kill it'
> proc.terminate()
> proc.join(3)
> print 'is it dead', proc.is_alive()
> if proc.is_alive():
> try:
> print 'force kill'
> os.kill(proc.pid, signal.SIGKILL)
> except Exception:
> pass
> proc.join(1)
> print 'alive', proc.is_alive()
> runtime = int(time.time() - now)
> raise TimeoutException('timed out after {0}
> seconds'.format(runtime))
> assert proc.done()
> success, result = proc.result()
> if success:
> return result
> else:
> raise result
> return inner
> return wrapper
>
> def term(*args):
> print 'term'
> time.sleep(4.0)
> print 'done'
>
> @timeout(5.0)
> def func():
> signal.signal(signal.SIGTERM, term)
> print 'sleep'
> time.sleep(10)
>
> def application(environ, start_response):
> status = '200 OK'
> output = b'Hello World!'
>
> func()
>
> response_headers = [('Content-type', 'text/plain'),
> ('Content-Length', str(len(output)))]
> start_response(status, response_headers)
>
> return [output]
>
> On 21/02/2015, at 10:23 PM, Paul Royik <[email protected]> wrote:
>
> I used this code:
> class TimeoutException(Exception):
> pass
>
>
> class RunableProcessing(multiprocessing.Process):
> def __init__(self, func, *args, **kwargs):
> self.queue = multiprocessing.Queue(maxsize=1)
> args = (func,) + args
> multiprocessing.Process.__init__(self, target=self.run_func,
> args=args, kwargs=kwargs)
>
> def run_func(self,
> ...
>
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