Why require_atomic? defaults to true?

Actions that cannot be performed atomically have some inherent issues. Specifically they are susceptible to having problems when operating concurrently. For example, if you insert a record, and then in between inserting it and doing some next step, that record has been deleted, you can find yourself in a bad state.

By setting require_atomic? to true, we make it more clear to users that they may need to handle these cases.

Is there any way to use “manage_relationship” with “require_atomic? true”?

No, not currently. There may be, with certain sets of options in the future though.

Ok, then can I think “In the future, most of the actions could be atomic with proper implementation.”?

It really just depends on the action. Being atomic is a property of the action. Some actions can be, some can’t be, it’s entirely based on what the action does.

Hmm.. Then I still cannot understand why require_atomic? defaults to true..
I think this would be the last question.

config :ash, :require_atomic_by_default?, false
Is this option “not recommended” or just “up to my choice”? @zachdaniel

I think most apps are

1. not that simple
2. has many actions that can’t be atomic

so most apps would use config above.

When this argument is brought up, in a lot of cases it points to poor design. If you cobble code together OFC you will end up with actions that are not atomic because you are always tempted to take the easy way out and do side effects as much as possible.

Happily enough, elixir and the VM limits drastically how many shortcuts of this type you can have by making the values immutable and having a clear concurrency concept.

I think you are not an ash framework user.
You don’t get what “not that simple” means.

Just one use of manage_relationship makes action not able to be atomic.
And manage_relationship is a basic feature in ash,
which is for creating two related resources in one action.

“Keep It Simple” is not “Always be simple”.
In complex problems, you can’t stay in simple.

require_atomic? is a safety guard. It’s like marking code as safe or unsafe in another language. It has little to no value if it defaults to false. It is expected that you will have to turn it off relatively often. That is still important though, as when you see that error you should consider if there is anything to be done for it.

This configuration:

config :ash, :require_atomic_by_default?, false, was made only to assist with the upgrade and will be removed in the future. I would not suggest using it at all.