Rails - Jun 2009 - Production vs Development I need to make different connections and call different code

Bare with me on this one....

We have a lot of read only data.  And it is accessed a lot more then
the user created data at this stage.  The datbase structure is (on
production):

production_user db

2 production_read_only databases behind HAProxy

So some models make a connection to the read_only databases through
HAproxy, which all works great.  The issue is that some of the user
created data that is stored in the production_user db needs to be
joined to the read only database at times.

So the scenario might be:
You have 5 kinds of apples all stored in the read only database, they
don''t change often.

But, a user comes and creates an account and picks his/her favorite
apples and saves that config.  On development you can use
has_and_belongs_to_many for both the user and apples and it works
great, all one database.

But, on production I need to store:
1) The user account on the production_user db
2) the HABTM table on the user db because the read only databases are
optimized for reads only and there are a lot of searches going on for
apples apparently :)

But, the apples themselves are on the read only database.  So if I say
apples.users or users.apples i need to make connections to pull the
interesting ides out of the corresponding tables, and make connections
to the other databases in order to get my data.

I could use a lot of
apple.users_from_production if RAILS_ENV == ''production''
apple.users unless  RAILS_ENV == ''production''
all over the place, but that seems hokie.

Anyone else had to do this and what was your solution?  Any help would
be appreciated.  Another solution would be helpful too, but the
database structure is pretty well set.  The readonly side needs to be
very scalable and nodes need to be able to disappear and reappear
based on load, hence haproxy so I can''t ''just go to one db and
use
memcache everywhere''. :D

Thanks.
Erik

> But, a user comes and creates an account and picks his/her favorite
> apples and saves that config.  On development you can use
> has_and_belongs_to_many for both the user and apples and it works
> great, all one database.
>
> But, on production I need to store:
> 1) The user account on the production_user db
> 2) the HABTM table on the user db because the read only databases are
> optimized for reads only and there are a lot of searches going on for
> apples apparently :)
>
Each model can use a different database connection. Assuming :readonly  
is a configuration defined in database.yml you can do

class Apple < ActiveRecord::Base
   establish_connection :readonly
end

to have it use that connection
> But, the apples themselves are on the read only database.  So if I say
> apples.users or users.apples i need to make connections to pull the
> interesting ides out of the corresponding tables, and make connections
> to the other databases in order to get my data.
>
> I could use a lot of
> apple.users_from_production if RAILS_ENV == ''production''
> apple.users unless  RAILS_ENV == ''production''
> all over the place, but that seems hokie.
>
> Anyone else had to do this and what was your solution?  Any help would
> be appreciated.  Another solution would be helpful too, but the
> database structure is pretty well set.  The readonly side needs to be
> very scalable and nodes need to be able to disappear and reappear
> based on load, hence haproxy so I can''t ''just go to one
db and use
> memcache everywhere''. :D
>
> Thanks.
> Erik
>
> >