Idempotency

How does Reboot handle idempotency?

Calls from code generated for React will use idempotency keys by default. Within Reboot, you only need to manually handle idempotency if you're trying to retry things manually in a client (using ExternalContext) or when writing a workflow method (using WorkflowContext, which is automatically retried).

If you're only trying to call a method of a specific state once using your context, you can call that method after using the fluent .idempotently() method, e.g., foo.idempotently().Method(context). If you need to call the same method on a state more than once, including when you're doing manual retries, then you can specify an idempotency "alias" to distinguish each call, for example:

Python

bank = Bank.lookup(SINGLETON_BANK_ID)

await bank.idempotently().SignUp(
    context,
    customer_name="Initial User",
)

TypeScript

await Bank.construct({ id: SINGLETON_BANK_ID })
  .idempotently()
  .signUp(context, { customerName: "Initial User" });

When you don't pass anything to .idempotently(), or when you just pass a string alias, Reboot will deterministically generate an idempotency key for you. You can also manually pass an idempotency key by calling .idempotently(key=...).

Why require idempotency?

Idempotency protects your system and your users against insidious distributed system bugs. Temporary network and server outages are always a risk when coordinating multiple machines, so it is often necessary to retry requests - opening up the possibility for a server to receive multiple requests when only one call was intended.

Idempotency does come with some storage overhead, but the protection it gives in return is a fundamental way in which Reboot keeps your system safe.