TimeOut with transaction block rails

Question

As my understanding, if we have any code inside this transaction and when it happens any error with (save!, ...) in that block the entire code will revert, here the problem is if any timeout (rack timeout = 12) happens in this block.

def create
  ActiveRecord::Base.transaction do
   // timeout happens
  end
end

How can we rollback a code with a transaction when a Rack::Timeout occurs?

Answer 1

When a Rack timeout happens, any transaction in process will be rolled back, but transactions that have already been committed will, of course remain committed. You should not have to worry about it.

Once you start a database transaction, it will eventually either be committed or rolled back. Those are the only two possibilities for ending a transaction. When you commit the transaction, you are saying that you want those changes to be saved regardless of what happens next. If you do not commit the transaction, the database will automatically rollback the transaction once it gets into any state where the transaction cannot move forward, such as a broken network connection.

ActiveRecord automatically commits the transaction when the ActiveRecord::Base.transaction do block exits normally. Abnormal exits may cause ActiveRecord to issue a ROLLBACK command to the database, which is efficient and good practice and returns the connection to a ready state, but it is not strictly necessary, because unless the transaction is explicitly committed, the database will eventually automatically roll it back.

Answer 2

If you look at ActiveRecord::ConnectionAdapters::TransactionManager#within_new_transaction on line 270 and 283 Rails is rescuing Exception. Rescuing Exception will catch anything and everything including kill commands and should generally be avoided. It is used in this case to ensure that no matter what is raised (including Rack::Timeout) the transaction will rollback.