How to change db connection on the fly in a rails app.

[antlypls]

Hey!

I'm using mongoid 2.2.3 in rails 3.0.10 app.
I've encountered in situation where i need to use multiple mongodb
databases in certain cases.
So I need to be able to switch db settings (different than in
config.yml) during request processing.
In my case it seems that the best place to do this is before_filter in
application controller.

I've found that following code allows to change db for same server^

class ApplicationController < ActionController::Base
before_filter :set_database

def set_database
Mongoid.master.connection.close
Mongoid.database = Mongoid.master.connection.db(db_name)
Mongoid.master.connection.connect
end
end

Is it good solution?

Another question is what is best solution to change whole connection
settings on the fly: host, port, db name?

[Durran Jordan]

That's probably the best way at the moment, but in 3.0.0 I'm going to change the internals to handle this on the fly with ease:

https://github.com/mongoid/mongoid/issues/1291

As for changing the entire connection, you could do it via:

Mongoid.master = Mongo::Connection.new.db("my_other_db_name")

2011/10/12 antlypls <antl...@gmail.com>

[Durran Jordan]

There are a myriad of ways now, but the most common is using #with:

Model.with(database: "other_db_name").create (works with any persistence call: create!, save, delete, etc)

See: http://mongoid.org/en/mongoid/docs/persistence.html#custom

2013/2/19 <louis....@gmail.com>

Hey Durran, has this been implemented in the end? What's the API for doing this?

Thanks,

Louis

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[Jon]

Hey Durran,

Is there a good way to do this in Mongoid 3 now that Mongoid.master= doesn't exist? We're tossing around the idea of completely partitioning clients in different databases, and updating the thousands of Model.where() or update calls to use Model.with(:session => SessionFactory.get_session_for_client()) isn't practical.

Something like a before filter might as antlypls originally suggested might be one way to approach it.

Jon

[Roman Gaufman]

We have a multi tenant app and we're doing this in a before_filter in our ApplicationController:

Mongoid.override_database("#{database_name}")

And this in our after_filter:

Mongoid.override_database(nil)

Works great :)

[Jonathan Hyman]

Thanks. We ended up writing an abstraction using thread-local storage, it works like the example on mongoid.org.

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[Steve Schlotter]

Roman,

I'm curious how this works.  

Does the user get directed to their database when they login using the database_name stored in their user record?  

And multiple users can be logged in and be using different databases simultaneously? 

Steve

[Steve Schlotter]

Jon,

Are you referring to the example here? http://mongoid.org/en/mongoid/docs/persistence.html#custom

[Jonathan Hyman]

Yeah, we use something like this pseudocode

store_in :session => lambda do

  Thread.current[:model_session_name] or raise StandardError.new("No session name defined")

end

This way, we catch all the places in code where we don't have something set.

[Roman Gaufman]

We do this from request.subdomain, each subdomain is a separate database

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