On Jun 6, 12:34 pm, Michael Bayer <[EMAIL PROTECTED]> wrote:
> On Jun 6, 2008, at 2:29 PM, qhfgva wrote:
>
>
>
>
>
> > We have (what I think of as) a moderately complicated database
> > configuration and I'm hoping there will be a way to configure
> > sqlalchemy to deal with it. The basic scenario is like this:
>
> > There are N mysql servers in different geographical regions that are
> > all replicating against one master. In the interest of speed the rule
> > in each location is to do reads which are very frequent against the
> > local copy of the database and if there is a write to do that against
> > the master. As an added wrinkle the user has an option to write to
> > the master with a master_pos_wait so that the current process will
> > wait until replication has caught up with the update just executed.
> > Hopefully that makes sense and gives enough of a flavor of what I've
> > got in mind.
>
> > I'm pretty new to sqlalchemy. Is the above feasible? If so are there
> > examples to compare with and learn from doing something similar?
> > Where (api/code) would I start looking to accomplish the above?
>
> > Any tips to get me going would be much appreciated.
>
> easiest approach is to use multiple sessions, multiple engines. Your
> app would need to know which engine it wants to talk to, and binds a
> session to that engine. Binding is described here:
> http://www.sqlalchemy.org/docs/04/session.html#unitofwork_getting_bin...
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).
In other words I'd like to have a handle to, say, a user object, and
do reads/updates to it with the programmer using this object not
caring about how the work gets done. So for instance I select a
number of user objects that come from the local database. Later I
update a field on one of these and the update takes place on the
master directly.
Is that weird? Doable? Unfortunately this is the environment I need
to get this working with.
As a side note, we manage this difference by hand now, it's really
annoying which is why I'd love to abstract it away.
thanks.
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