如何使用around_action包装每个Rails ActiveRecord查询

Question

I would like to create a module that when included, makes every active record query execute as a block that I will wrap.

Specifically I'm using https://github.com/zendesk/active_record_shards to shard to multiple databases. In this scenario we have 10 duplicate databases (same schema but different client instances) and 1 unique database. By default, any calls to our models that belong to the 10 duplicate databases will be wrapped in an application controller around_action that does

ActiveRecord::Base.on_shard(database_name) do
  yield
end 

However we have a set of models that should only execute queries against this 1 unique database. Rather than execute every ActiveRecord query on those models using something like

ActiveRecord::Base.on_shard('unique_db') { Model.find(id) }

I would rather make a module that when included executes the active record query as a block inside the on_shard method so they always execute agains the unique_db

Let me know if I'm going down the wrong path and should just stick with my helper method which basically just shortens the length

module UniqeDB
  def self.exec!
    ActiveRecord::Base.on_shard('unique_db') do
      yield
    end
  end
end

Thanks!

Update: I was able to do something like this, however it overrides every method with (*args, &block) however some methods (like default_scope) only take a block and then it throws exceptions

included do
  ActiveRecord::Base.methods.each do |name|
    define_singleton_method name do |*args, &block|
      ActiveRecord::Base.on_shard('unique_db') do
        super(*args, &block)
      end
    end
  end
end

Update: I opened an issue with the gem to see if there is something i'm missing https://github.com/zendesk/active_record_shards/issues/87

Answer 1

Include the below module in any controller like ' include ExecuteInUniqueDB '

All action inside the controller will only in unique_db

module ExecuteInUniqueDB
  def self.included(base)
    base.class_eval do
      around_action :run_on_unique_db
    end
  end

  def run_on_unique_db(&block)
    ActiveRecord::Base.on_shard('unique_db', &block)
  end
end