On Thu, 2005-09-29 at 16:15 +0100, Nuno Pereira wrote:
> [EMAIL PROTECTED] wrote:
>
> This one is interesting in terms of concurrency...
>
> Is the app2 the one responsable for setting the flag? I supose that it is.
> If that happens it's important that app2 doesn't mess with the flag, i
> mean, it may lead to problems if app2 sees that app1 writes the sales
> data, app2 sees it, starts reading it, app1 writes more data and app2
> sets the flag without seeing that app1 have written more data, and sets
> the flag without reading the new one.
>
> Make this work without problems can be tricky, and I don't see a good
> solution to this in five minutes. When app2 reads data what app does
> with it? How app2 sees what was the last data she read?
>
> --
> Nuno Pereira
>
I don't think there is any concurency problem:
App 2 sets the flag and then polls for it to be unset, it is unset by
app 1 when it has written all of the sales data. meanwhile app 2 is
polling for the flag to be unset again and does nothing until it is, if
app 1 dies before unsetting the flag app then app 2 will sit in a loop
forever.
when the flag is unset, app 2 reads it, process it and posts it to a
website via xmlrpc
app 2 site in a shell script while loop: (pseudocide)
while (1){
start app 2
sleep (60)
}
so there can never be more than one instance of app 2 running.
tony
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