If you positively cannot have overbooking (oops, airline talk) over-selling, then all your orders have to either lock a table (using the database to enforce serialization), or they have to be serially examined in someway, such as a single order FIFO queue. You could create an observer, for example, that monitors the creation of an order, checks to see if stock (tickets, seats, CD's, whatever) is available; and gracefully back-out an order that "goes over." Personally, I would be tempted to try a simple solution, like a queue of some sort first, or perhaps an observer, rather than use the database. This is one of those cases where trying to optimize too early may hurt. A simple, single, global queue may be all you need. YMMV. Cheers--
Charles On Wed, Apr 15, 2009 at 3:02 AM, Frederick Cheung < frederick.che...@gmail.com> wrote: > > On Apr 14, 10:55 pm, steveluscher <goo...@steveluscher.com> wrote: > > What do you think is the best way to prevent overselling in this case? > > I've considered: > > > > * Table locking (sucks) > > * Setting a lock file per-Product (filesystem-y and not elegantly > > scalable past one machine) > > * Setting a lock variable per-Product in a memcached store > > * A single-worker queue that validates and processes orders in > > sequence > > * A per Product single-worker queue that validates and processes > > orders in sequence > > * Something I haven't considered? > > > > It sort of depends where the information that only 3 more orders for > Product X lives. > For example if the products table has a stock_remaining column, then > for me the natural thing to do would be to use optimistic locking on > the products table > I wrote up some possibilities at > http://www.spacevatican.org/2008/6/8/dealing-with-concurrency > > Fred > > What do you think? > > Steve! > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
