CODEWITHSUNDEEP
mysqlruby-on-railsrails-engines
Gaurav Singh
Gaurav Singh

Reputation: 51

Rails Engines with multiple databases

I am creating application in Ruby on Rails which is having many engines(for modularity).

I want different databases for each engine. How to configure this?

Database - MYSQL

Upvotes: 4

Views: 1520

Answers (2)

x'ES
x'ES

Reputation: 574

General approach is to take a look at the framework sources and decide can it be reused.

Let's take a look at activerecord/lib/active_record/railties/databases.rake (v5.0.7) first. For example on how db:create implemented.

We will see ActiveRecord::Tasks::DatabaseTasks.create_current.

Let's open ActiveRecord::Tasks::DatabaseTasks and take a look at

    # The possible config values are:
    #
    # * +env+: current environment (like Rails.env).
    # * +database_configuration+: configuration of your databases (as in +config/database.yml+).
    # * +db_dir+: your +db+ directory.
    # * +fixtures_path+: a path to fixtures directory.
    # * +migrations_paths+: a list of paths to directories with migrations.
    # * +seed_loader+: an object which will load seeds, it needs to respond to the +load_seed+ method.
    # * +root+: a path to the root of the application.
    #
    # Example usage of DatabaseTasks outside Rails could look as such:
    #
    #   include ActiveRecord::Tasks
    #   DatabaseTasks.database_configuration = YAML.load_file('my_database_config.yml')
    #   DatabaseTasks.db_dir = 'db'
    #   # other settings...

This way we are getting to following solution:

namespace :your_engine do
  namespace :db do

    task :load_config do
      ActiveRecord::Tasks::DatabaseTasks.database_configuration = YAML.load_file("config/database_your_engine.yml")
      ActiveRecord::Tasks::DatabaseTasks.db_dir = "db_your_engine"
      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = [ "components/your_engine/db/migrate" ]

      ActiveRecord::Base.configurations = ActiveRecord::Tasks::DatabaseTasks.database_configuration
      ActiveRecord::Migrator.migrations_paths = ActiveRecord::Tasks::DatabaseTasks.migrations_paths

      # You can observe following values to see how settings applied.
      # puts ActiveRecord::Base.configurations
      # puts ActiveRecord::Migrator.migrations_paths
      # puts ActiveRecord::Tasks::DatabaseTasks.database_configuration
      # puts ActiveRecord::Tasks::DatabaseTasks.migrations_paths
    end

    desc "Create Your DB"
    task create: :load_config do
      ActiveRecord::Tasks::DatabaseTasks.create_current
    end
  end
end

The same approach for drop/migrate and other needed tasks.

It is good general rule - know you stack at least one level lower than your work with. Sometimes reading underlying sources much more helpful than direct answer.

I will update this answer while going forward with my solution...

Upvotes: 1

Pavel Pachkovsky
Pavel Pachkovsky

Reputation: 371

There is a good explanation by the link http://www.blrice.net/blog/2016/04/09/one-rails-app-with-many-databases/

Upvotes: 3

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