How to force Rails ActiveRecord to commit a transaction flush

Question

Is it possible to force ActiveRecord to push/flush a transaction (or just a save/create)?

I have a clock worker that creates tasks in the background for several task workers. The problem is, the clock worker will sometimes create a task and push it to a task worker before the clock worker information has been fully flushed to the db which causes an ugly race condition.

Using after_commit isn't really viable due to the architecture of the product and how the tasks are generated.

So in short, I need to be able to have one worker create a task and flush that task to the db.

Answer 1

ActiveRecord uses #transaction to create a block that begins and either rolls back or commits a transaction. I believe that would help your issue. Essentially (presuming Task is an ActiveRecord class):

Task.transaction do
  new_task = Task.create(...)
end

BackgroundQueue.enqueue(new_task)

You could also go directly to the #connection underneath with:

Task.connection.commit_db_transaction

That's a bit low-level, though, and you have to be pretty confident about the way the code is being used. #after_commit is the best answer, even if it takes a little rejiggering of the code to make it work. If it won't work for certain, then these two approaches should help.

Answer 2

execute uses async_exec under the hood which may or may not be what you want. You could try using the lower level methods execute_and_clear (or even exec_no_cache) instead.