> On Feb 20, 2017, at 00:58, Роман Мещеряков <[email protected]>
> wrote:
>
>
> Hi everyone,
>
> The answers are below
>
> --
> Kind regards, Roman Mescheryakov
>
>
> 19.02.2017, 02:21, "Jean-Paul Calderone" <[email protected]
> <mailto:[email protected]>>:
>> On Sat, Feb 18, 2017 at 2:25 PM, Glyph Lefkowitz <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>>> On Feb 2, 2017, at 1:17 AM, Роман Мещеряков <[email protected]
>>> <mailto:[email protected]>> wrote:
>>>
>>> Hello everyone! I wrote Twisted-based TCP server which is capable of
>>> running in several relatively different modes. When mode switch is needed,
>>> I would like the server to restart itself by some means, for it to read new
>>> mode from configuration file and create corresponding implementation. Also
>>> I wanted the restart to occur without re-running twistd process, because it
>>> seems to me more appropriate for Linux daemon.
>>
>> Hi Roman,
>>
>> Sorry it took a while to get to this one :).
>>
>> If your solution is working for you, then it's fine. You've correctly
>> understood the API associated with IServiceCollection and your
>> implementation (at least at first glance, I don't have time to test it
>> exhaustively :)) is correct.
>>
>> However, there's a more philosophical question as well: if you really want
>> to re-start from scratch, what exactly are you shutting down and starting up
>> again? Wouldn't you want to be able to load new code? Simply stopping and
>> starting objects won't re-initialize the process from the beginning, only
>> from some indeterminate middle state where parts of the program are already
>> set up; this doesn't have the usual desired effect of a "restart" where
>> potentially unknown or buggy state is cleared away.
>>
>> You may want to consider simply calling execv
>> https://docs.python.org/2.7/library/os.html#os.execv
>> <https://docs.python.org/2.7/library/os.html#os.execv> with [sys.executable]
>> + sys.argv rather than trying to do this in terms of Twisted's APIs.
>
> You are right, Glyph, using os.execv would be more simple, reliable and
> straightforward way of achieving my goal. The only thing that bothers me due
> to lack of Linux experience: is it OK to os.execv inside daemon process?
> Because I run my process using twistd, not python directly.
If you're actually daemonizing ('twistd' without '-n') then there might be a
small issue. However, a modern best practice is to never daemonize; this is
why the new `twist` runner (which you should probably switch to) doesn't
daemonize and expects your supervisor to handle backgrounding.
>>
>> Or better yet. Don't be afraid to just exit. Your process is being managed
>> by a supervisor with a rich feature set - like easily controlled re-restart
>> behavior, right (If not, what do you do when your daemon simply crashes)?
>>
>
> Well, in fact I'm in the development stage now and did't have time to deal
> with this question yet :) As of now I understand very little about daemons
> and their supervisors (I belive it is systemd for Raspbian...).
Yes, systemd will do this.
> Jean-Paul and Glyph, thank you for guiding me in the right direction! :)
>
>
Happy to help!
-g
>> Jean-Paul
>>
>> ,
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