Comment by stuhood
3 months ago
They are related, for sure. But one of the biggest differences is that operations affecting multiple Reboot states are transactional, unlike Azure's "entity functions".
Because multiple Azure entity functions are not updated transactionally, you are essentially always implementing the saga pattern: you have to worry about cleaning up after yourself in case of failure.
In Reboot, transactional function calls automatically roll back all state changes if they fail, without any extra boilerplate code. Our hypothesis is that that enables a large portion of an application to skip worrying about failure entirely.
Code that has side-effects impacting the outside world can be isolated using our workflow mechanism (effectively durable execution), which can themselves be encapsulated inside of libraries and composed. But we don't think that that is the default mode that developers should be operating in.
Could you expand on this part?
> Code that has side-effects impacting the outside world can be isolated using our workflow mechanism (effectively durable execution
Sounds very interesting!
I have been thinking about something like this for a new PL, and many kinds of side effect can actually be reversed, as if it never happened.
I have also read that exceptions can complicate control flow, disallowing some optimizations - but if they are transactional, then we can just add their reverse to the supposedly already slow error path, and enjoy our performance boost!
Every method in Reboot has a type: reader, writer, transaction, or workflow. Our retry semantics are such that any method can always be retried from the top, but for different reasons:
In readers, no state changes are possible. And in writers and transactions, retry/abort is always safe because no state changes occur until the method completes successfully.
In workflows, retry is always safe, and is in fact required due to the primitives we use to implement durable execution (we will publish more docs on this soon!). The workflow retries durably until it eventually completes, one way or another.
That means that a workflow is always the right spot to execute an external side effect: if a reader/writer/transaction want to execute a side effect, they do so by spawning a task, which is only actually spawned if the method completes successfully. And we do "effect validation" (effectively: running your method twice!) to make it very hard to write a side effect in the wrong place.
https://docs.reboot.dev/develop/side_effects has some more details on our approach to side effects, but feel free to follow up in our discord too: https://discord.com/invite/cRbdcS94Nr
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> I have also read that exceptions can complicate control flow, disallowing some optimizations - but if they are transactional, then we can just add their reverse to the supposedly already slow error path, and enjoy our performance boost!
Somewhat...! When you write a transaction method in Reboot, code that fails with an exception cannot have had a side effect on the outside world, and all state changes will vanish if the transaction aborts. So there is never any need to clean something up, unless you are using exceptions to implement control flow.