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Journaling Results

Restate uses an execution log for replay after failures and suspensions. This means that non-deterministic results (e.g. database responses, UUID generation) need to be stored in the execution log. The SDK offers some functionalities to help you with this:

  1. Journaled actions: Run any block of code and store the result in Restate. Restate replays the result instead of re-executing the block on retries.

Journaled actions

You can store the result of a (non-deterministic) operation in the Restate execution log (e.g. database requests, HTTP calls, etc). Restate replays the result instead of re-executing the operation on retries.

Here is an example of a database request for which the string response is stored in Restate:

async def do_db_request():

    # ... implement ...

    return "my_result"



result = await ctx.run("database request", do_db_request)

You cannot use the Restate context within ctx.run. This includes actions such as getting state, calling another service, and nesting other journaled actions.

You can return any payload that can be serialized with bytes(json.dumps(obj), "utf-8") and deserialized with json.loads(buf). If not, you need to specify a custom serializer.

Immediately await journaled actions

Always immediately await ctx.run, before doing any other context calls. If not, you might bump into non-determinism errors during replay, because the journaled result can get interleaved with the other context calls in the journal in a non-deterministic way.