On Jun 9, 2008, at 4:57 PM, Jonathan LaCour wrote:
> > Michael Bayer wrote: > >>> Thanks I'll take a look. I left out what I think is an >>> important part of this scenario (or maybe it's trivial - I don't >>> have a good perspective on this yet). In any case, I would like >>> to use the ORM component of sqlalchemy and completely hide the >>> fact that the read/ write connections are possibly different. >>> (They might become the same connection if the local database >>> becomes unaccessible and/or is too far behind the master). >> >> that is going to be very hard to accomplish as the Session does >> not have a clustering rules engine built into it in order to >> determine read/write locations, nor is that within its scope. It >> can only handle "class X talks to engine Y". > > Just an FYI, I am actually splitting reads and writes in a fairly > straightforward way in my web application by inferring the intent > of the request based upon the method. We developed the application > so that all requests that write to the database are in a POST. > Everything else uses other methods (primarily GET). > > We use a scoped session, ensuring that each request gets its own > session and then wrote some WSGI middleware which will automatically > bind the session to the correct database instance (one of the > masters, or the correct slave) based upon the request method. We > also automatically wrap POST's in a transaction, and roll back upon > errors. > > FWIW, this middleware is like 20 lines of code long. If your app > is not web-based you might have trouble getting away with something > like this :) yup, my approach for this uses decorators: @readonly def do_something_readonly(request_vars): @writeable def do_something_writeable(request_vars): the scoped_session is configured by the decorator. but this still has an "explicit"ness to it that it seemed the poster was looking to avoid. but perhaps I mis-read. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
