On Tue, Jun 24, 2014 at 2:54 PM, Mike Copeland <m...@ggisoft.com> wrote:
> Simplified scenario...
> 2 Windows computers using a VFP9 SP2 application, served by 1 MySQL
> (MariaDB) server on Linux box
>
> What is the best way for computer #1 to "do something" and have computer
> #2 detect that change?
> (for example, save a new record on the server for a processed shipment)
>
> What my feeble mind has thought of so far...
> -- #2 uses a timer to query the server for changes (lotsa traffic!
> especially with dozens of workstations)
>
"DOES NOT SCALE" is the fashionable criticism these days. In your situation
of 2 computers, this is fine. For dozens, not so much of a problem: a dozen
pre-compiled queries every five seconds is trivial bandwidth and process.
Now, if you're scaling to tens of thousands, or millions, you need to
reconsider your strategy.
> -- #1 'signals' #2 somehow using Windows API (never done anything like
> this)
>
Bad idea on so many levels. You've gone from a client-server app to a
peer-to-peer app. And does Computer #1 signal ALL the computers that are
somehow registered as being attached when this is multi-user. Things get
out of hand, geometrically.
> -- a better way I'm oblivious to (no surprise!)
>
> Is there a better way?
>
Refine your scenario. If this is just "the shipping computer needs to know
if there's more work to do, once an order is posted," then, yes, querying a
queue of work to be done ("SELECT NEXT 1 * from ORDERS WHERE tTimeStamp >
ltLastChecked") is the simplest. It can scale to multiple computers doing
the query with a simple flag for each to call dibs when they lock an order
to process.
If this is a more complex process, simplified for asking the question,
well, you're just going to get simple answers :) There are all sorts of
techniques for workflow processing, message queueing and process
orchestration.
>
> Mike Copeland
>
[excessive quoting removed by server]
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