[Twisted-Python] Twisted and Thread, thread not running when twisted app is running as service

[Barry Scott]

On Thursday, 21 May 2020 21:45:44 BST Sereysethy TOUCH wrote:
> I am on MacOS, it is a development phase, but deployment will be on Linux.
> 
> It is hard to run dtrace/dtruss on MacOS due to the "system integrity
> protection" on MacOS. I got some output but very limited information.
> 
> So if there is a workaround you might suggest?

Why bother debugging it on macOS it never has to work there?

If you are targetting linux then develop and test in linux I'd recommend.
I use VMware fusion on the mac and run VMs for the target
environements I need. Works very well.

Barry

> 
> TS
> 
> On Thu, May 21, 2020 at 10:20 PM Jean-Paul Calderone <
> 
> exarkun at twistedmatrix.com> wrote:
> > On Thu, May 21, 2020 at 3:56 PM Sereysethy TOUCH <
> > 
> > touch.sereysethy at gmail.com> wrote:
> >> Hi Jean-Paul,
> >> 
> >> I found the error after working on a short, self contained, correcte
> >> example. It is not about twisted and normal thread in general, but
> >> something else.
> >> 
> >> After more tests, I come to realise that whenever I instantiate this
> >> class PolicyClient from this library
> >> https://github.com/ray-project/ray/blob/master/rllib/env/policy_client.py
> >> in my protocol or just anywhere, twisted app either freezes or
> >> terminates, and this *only* happens when the app runs as a daemon,
> >> created using a service (.tac file).
> >> 
> >> I hope you can take a look at the class PolicyClient, why it causes
> >> problem to reactor main loop. Please point me to where the idea might
> >> come
> >> from.
> >> 
> >> I can give you the example but not sure if it is enough, as the client
> >> needs to connect to a server.
> > 
> > It looks like PolicyClient does a blocking HTTP request in __init__.
> > Since PolicyClient is instantiated in the reactor thread, this will block
> > the reactor.  Perhaps this call is hanging for some reason when the
> > process
> > has daemonized?  This would be unusual but not unheard of.  For example,
> > there are macOS environments where a process does not have access to the
> > network if it is not associated with a windowing session.
> > 
> > What platform do you observe the problem on, and what more can you learn
> > about what the process does on its way to hanging (eg can you run strace
> > on
> > it)?
> > 
> > Jean-Paul
> > 
> >> Thank you,
> >> TS
> >> 
> >> 
> >> On Thu, May 21, 2020 at 5:23 PM Jean-Paul Calderone <
> >> 
> >> exarkun at twistedmatrix.com> wrote:
> >>> On Thu, May 21, 2020 at 10:58 AM Sereysethy TOUCH <
> >>> 
> >>> touch.sereysethy at gmail.com> wrote:
> >>>> Hello,
> >>>> 
> >>>> I am developing a twisted app, and it runs as a service using twistd -y
> >>>> to start the app.
> >>>> I am having a problem of running a thread. I know it is not recommended
> >>>> to use thread, but the library that I use, the object created is
> >>>> running in
> >>>> a thread.
> >>>> 
> >>>> Here is the problem:
> >>>> 
> >>>> 1) if I start reactor by running reactor.run() directly, thread is
> >>>> running fine
> >>>> 2) if I run it as a service using twisted, the thread is not running,
> >>>> it runs but it seems to be blocked, because I tried to write something
> >>>> to
> >>>> file using time.sleep(), but file is empty.
> >>>> 
> >>>> Is there something that I miss? How can I debug this?
> >>> 
> >>> A good next step would be to create at Short, Self Contained, Correct
> >>> (Compilable), Example <http://sscce.org/> and share it.
> >>> 
> >>> Jean-Paul
> >>> 
> >>>> Thank you,
> >>>> 
> >>>> TS
> >>>> _______________________________________________
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