Commit a nested transaction

Question

Let's say I have a method that provides access to an API client in the scope of a user and the API client will automatically update the users OAuth tokens when they expire.

class User < ActiveRecord::Base

  def api
    ApiClient.new access_token: oauth_access_token,
                  refresh_token: oauth_refresh_token,
                  on_oauth_refresh: -> (tokens) {
                    # This proc will be called by the API client when an 
                    # OAuth refresh occurs
                    update_attributes({
                      oauth_access_token: tokens[:access_token],
                      oauth_refresh_token: tokens[:refresh_token]
                     })
                   }
  end

end

If I consume this API within a Rails transaction and a refresh occurs and then an error occurs - I can't persist the new OAuth tokens (because the proc above is also treated as part of the transaction):

u = User.first

User.transaction { 
  local_info = Info.create!

  # My tokens are expired so the client automatically
  # refreshes them and calls the proc that updates them locally.
  external_info = u.api.get_external_info(local_info.id)

  # Now when I try to locally save the info returned by the API an exception
  # occurs (for example due to validation). This rolls back the entire 
  # transaction (including the update of the user's new tokens.)
  local_info.info = external_info 
  local_info.save!
}

I'm simplifying the example but basically the consuming of the API and the persistence of data returned by the API need to happen within a transaction. How can I ensure the update to the user's tokens gets committed even if the parent transaction fails.

Answer 1

Have you tried opening a new db connection inside new thread, and in this thread execute the update

    u = User.first

    User.transaction { 
       local_info = Info.create!
   
       # My tokens are expired so the client automatically
       # refreshes them and calls the proc that updates them locally.
       external_info = u.api.get_external_info(local_info.id)

       # Now when I try to locally save the info returned by the API an exception
       # occurs (for example due to validation). This rolls back the entire 
       # transaction (including the update of the user's new tokens.)
       local_info.info = external_info 
       local_info.save!

       # Now open new thread
       # In the new thread open new db connection, separate from the one already opened
       # In the new connection execute update only for the tokens
       # Close new connection and new thread
       Thread.new do
          ActiveRecord::Base.connection_pool.with_connection do |connection|
             connection.execute("Your SQL statement that will update the user tokens")        
          end
       end.join
    }

I hope this helps