make queries on multiple db in same action controller with transaction rails? - mysql

Question

I have in my database.yml :
default: &default
[...]
development_1:
<<: *default
database: dev1
development_2:
<<: *default
database: dev2
I need to make many queries in foo action but using these 2 DB :
class UsersController < ApplicationController
def foo
users_nb = User.count #this use my default db : dev1
other_connexion = ActiveRecord::Base.establish_connection("#{Rails.env}_2").connection
users_nb_other_site = connexion.execute("SELECT COUNT(*) FROM users").first[0]
end
end
that works, BUT I encapsulate all action controller in transaction like :
ActiveRecord::Base.transaction do
begin
yield
rescue Exception => e
raise ActiveRecord::Rollback
end
with this, my previous code doesn't works, it raise an error :
ActiveRecord::StatementInvalid in UsersController#foo NoMethodError:
undefined method `query' for nil:NilClass Did you mean? to_query:
ROLLBACK
the line of error is : ActiveRecord::Base.transaction do
So how can I do to make my connexion and queries on another db in same time that my principal db?

Answer 1

Ok, my problem was I don't understand ActiveRecord::Base.establish_connection overwrite my first connexion and the transaction too.
I create an abstract class like said here : https://makandracards.com/makandra/10169-when-connecting-to-a-second-database-take-care-not-to-overwrite-existing-connections
class ReadDatabaseConnection < ActiveRecord::Base
def self.abstract_class?
true # So it gets its own connection
end
end
ReadDatabaseConnection.establish_connection(slave_settings)
I keep my 2 connexion like that, without pb !