[Info-vax] OT: Record locking for web transactions

[David Froble]

Jan-Erik Soderholm wrote:
> JF Mezei wrote 2014-02-17 21:13:
>>
>> With RMS, things were simple. the process running the UI also had the
>> record locks. If process dies, any/all locks are released.
>>
>> How does one handle this with web transactions ?
>>
> 
> The web is basicaly stateless, so you never keep locks from one
> access to another.

This is also my understanding.  Basically, you're talking about a 
different environment and concepts than what we all grew up with.

Note, all this is assuming that you're working with users running a browser.

Let's say that you have a web site selling chocolates.

You get an incoming request.  A user wants to see what you have.

You prepare a page showing your inventory, and sent it to the user.  At 
that time, you have no idea if the user will ever be back.  Maybe he 
found chocolate elsewhere, and was just comparing.

Next, you get another connection request, and it contains the page info 
you sent out, and an order for various products.  (Let's leave out 
credit card payment for now.)  At this time you actually have something 
to do.  You extract the information, name, shipping address, types of 
chocolate, quantities, basically what you need to process an order.  So, 
you can now read and lock data, update, and write, and whatever else 
required.

There is no connection between transmissions from the client, except 
return data from whatever you sent out.  So the first page you sent out 
should have whatever you need to process the customer's order.

This is a rather simplistic explanation, and I'm sure there is more that 
can be done.  But the key is "stateless transactions".

Frankly, I think that it's a big step backwards, sort of like the old 
IBM terminals where an entire form was filled out before sending 
anything to the computer, but even worse.  But nobody is asking me.

Now, if I was designing the concepts, it would be something more like a 
"connected terminal", perhaps some code that ran on the client system, 
and communicated back and forth with the server.  What do you do when 
someone turns off their terminal and walks away?  Perhaps you cancel any 
partial transactions?  Similar could be done, with timeouts and such. 
First timeout, "do you need more time?", and second timeout trashes the 
entire thing.

Or have an open socket connection, and if it goes down, trash the entire 
thing, sort of like with the old modems, lose carrier, and you lose your 
loged in process.

But again, nobody asked me ....