suggestion on a complicated inter-process communication

[Way]

Thanks a lot for reply. I understand it is abnormal to implement such
IPC, while it is worthy for my application.

Well, my process3 and 4 are from an outside application, which both
need License Check and os.system to involk.

>From my experience, if Process5 involks Process3, such License Check
can be very very slow (even slower than its real run).

That is why I need to separate Process3 and 4 onto different processes
to proceed.

On Apr 28, 1:57 am, Jonathan Gardner <jgard... at jonathangardner.net>
wrote:
> On Apr 27, 8:59 pm, Way <csw... at gmail.com> wrote:
>
>
>
> > Hello friends,
>
> > I have a little messy situation on IPC. Please if you can, give me
> > some suggestion on how to implement. Thanks a lot!
>
> > -> denotes create
>
> > MainProcess -> Process1 -> Process3 (from os.system)
> >                    |
> >                     -> Process2 (from os.system) -> Process4 (from
> > os.system) ->Process5
>
> > I would like to make the communication between Process1 and Process5.
> > Process1 needs Process5's output to provide argument to generate
> > Process3, and in turn Process5 needs to wait Process3 finished.
>
> > Thank you very much if you can give a hint.
>
> Abstraction should resolve this. What I mean is that Process2
> shouldn't be defined in terms of what it actually does, but what it
> appears to do. If you look at each process and think only what its
> child processes do and what its parent process expects it to do, then
> your job should get a lot simpler. Process1 expects Process2 to
> deliver a set of parameters to spawn Process3, and then it will wait
> until Process3 terminates.
>
> Looking at it this way, questions come to mind: Why can't Process2 run
> Process3 itself? It's unusual to have one process tell another process
> what to do when it can simply do it itself.
>
> By the way, I've never seen a time when this kind of design is
> necessary. There are other ways around your problem than spawning a
> bunch of processes. Each process should really be independent of all
> the other processes, doing only a very well-specified task in a well-
> specified way. The only time I could think of doing something like
> this is when you're getting a webserver setup and Process5 needs to
> communicate with Process3 to render the page or something like that.
> But even in that case, each process is really independently defined
> and implemented.