Non-GUI, single processort inter process massaging - how?

Chris Green cl at isbd.net
Sat Jul 21 10:33:16 EDT 2018


Steven D'Aprano <steve+comp.lang.python at pearwood.info> wrote:
> On Sat, 21 Jul 2018 09:07:23 +0100, Chris Green wrote:
> 
> [...]
> > I want to be able to interrogate the server process from several client
> > processes, some will interrogate it multiple times, others once only. 
> > They are mostly (all?) run from the command line (bash).
> 
> 
> This sounds like a good approach for signals. Your server script sets up 
> one or more callbacks that print the desired information to stdout, or 
> writes it to a file, whichever is more convenient, and then you send the 
> appropriate signal to the server process from the client processes.
> 
[snip useful sample scripts]

Yes, maybe, though I was hoping for something a bit more sophisticated.

At the moment it's the 'client' processes which manage the output side
of things, pushing it across to the 'server' would mean that the
client does nothing except send a signal.  As the outputs are to quite
a variety of things (e.g. terminal  screen, serial connection, LCD
display) this would push a lot of code to the server which currently
is quite nicely separated into client modules.

Communicating by file is a possible approach I had considered though,
the server can do its smoothing etc. of results and write them to a
file which is then read as required by the client processes.  The only
issue then is the need for some sort of locking as one doesn't want
the client to read while the server is writing.  One could overcome
this by using a temporary file though, mv/rename is supposed to be
atomic.

Going back to my original request the clients don't really need to be
able to 'interrogate' the server, they just need to be able to access
results produced by the server.  So maybe simply having the server
write the values to file is all that's really needed.

-- 
Chris Green
·


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