RE: [PHP] operational musings

The company I work for is currently doing this... using PHP in a retail
environment, with a Linux server in every store, talking to the POS
controller via a socket, storing data in a database (postgres), and
processing retail transactions in real-time. And, sending results of
those transactions to a central server (which isn't running Linux, PHP,
or Apache).

I'm finding the PHP socket support to be unreliable, though.

Everything's fine when we have one socket open to talk to the store
controller. I open the socket and bind to an address:port, the store
controller connects to it just fine, and we move on.

However, right now, we're using Postgres as a queue between two programs
that are processing transactions. I'm trying to get rid of Postgres and
use a pair of IPC sockets (created with socket_create_pair() and using
pcntl_fork()).

The IPC sockets seem to be totally unreliable, at this point.
Sometimes, when I call socket_write(), the function just never returns.
My application doesn't die.... but, the line of code immediately
following the socket_write() function never gets executed in the parent
process. The child process receives the data and logs it successfully.
So, I know the socket_write function is getting called and doing
something. It just never returns.

Anyone here have any ideas?

I can send more details, and even chunks of pertinent code.

-----Original Message-----
From: Robert Cummings [mailto:robert@xxxxxxxxxxxxx]
Sent: Tuesday, February 27, 2007 8:13 PM
To: Jay Blanchard
Cc: php-general@xxxxxxxxxxxxx
Subject: Re: [PHP] operational musings

On Tue, 2007-02-27 at 18:59 -0600, Jay Blanchard wrote:
Howdy cats and kittens!

I had an interesting thought after watching a demo of a POS
system and
wondered if the same type of methodology could be applied in a PHP
application. I haven't thought this all the way through, but a
fully-hatched idea like this could signal a major change in
applications
designed with PHP.

In the POS if the network connectivity was lost the store
could continue
to operate, once the network connectivity was restored the data from
each store would sync back up and data would be sent to the central
server, yadda, yadda, yadda. Of course this is in a client/server
application with an executable residing on each workstation.

So, if you wanted to do this with PHP you would likely have
to have a
local web /database server (each store), establish a socket
(primary and
store servers?) to watch for an outage/restore and then
write the code
to support the sync up. Can it be done with PHP? It would
definitely be
worth the trouble given the frequency that connections to stores get
lost.

Let's make a check list:

local webserver -- check
local database server -- check
socket support -- check
write code -- check

All signs point to YES :)

Cheers,
Rob.
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