Rolling back on failure when using multiple databases using Ecto.Multi

Questions / Help
,
1

Hello, I’m using Ecto for a project or mine and I’m running into issues with the rollback not working with a failed Ecto.Multi transaction that spans multiple databases. Is this not possible? Am I missing something?

Here’s a bit clearer example:

Multi.new
|> Multi.run(:db1, fn _, _ -> ModuleA.does_some_data_transformation_in_a_transaction_on_repo1() end)
|> Multi.run(:db2, fn _, _ -> ModuleB.does_some_data_transformation_in_a_transaction_on_repo2() end)
|> Multi.run(:db3, fn _, _ -> ModuleC.does_some_data_transformation_in_a_transaction_on_repo3() end)
|> Repo3.transaction()

If the :db3 step fails the other two transactions aren’t rolled back. Is there a way to achieve this?

2

Ecto multi works by utilizing underlying database transaction mechanics, not by adding its own. Cross database transactions are not possible. You may want to check out something like https://medium.com/nebo-15/introducing-sage-a-sagas-pattern-implementation-in-elixir-3ad499f236f6 which can implement a notion of rolling back that isn’t dependent on database level transactions.

4 Likes