Question about Clickhouse end-to-end acknowledgments

[bmtcril]

Question

The Clickhouse sink reports that it supports end-to-end acks, I'm just curious about the mechanism. My guess is that it's separate from the async insert settings, in which case the writes can still fail without the source knowing (if query_settings.async_insert_settings.enabled is true and async_insert_settings.wait_for_processing is false).

I just want to confirm the behavior so I can document it for my users.

Vector Config

No response

Vector Logs

No response

[SergkeiM]

Hi @bmtcril

Did you managed to find an answer for this?

[bmtcril]

I haven't heard anything back, but I think it would be impossible to have true e2e acks if at least wait_for_processing isn't true. It would still catch things like being unable to connect to the db, or timeouts, etc. though.

[pront]

Yes, your understanding is correct. With end-to-end acknowledgements enabled, Vector acknowledges successful delivery based on the ClickHouse HTTP response. It does not separately check whether an asynchronous insert succeeded after that response.

With async_insert_settings.enabled: true:

• wait_for_processing: false maps to ClickHouse's wait_for_async_insert=0. ClickHouse can acknowledge the data while it is still buffered. A later insert failure cannot be reported back through the already-completed Vector request.
• wait_for_processing: true maps to wait_for_async_insert=1. ClickHouse waits for the buffered insert to finish and returns processing errors to the client. This is the mode to use when acknowledgements should cover asynchronous insert processing.

These settings live under query_settings. Also enable acknowledgements.enabled on the sink and use a source that supports acknowledgements. See ClickHouse's return-mode documentation.

Verified on Vector 0.60.0 with an HTTP source and a mock ClickHouse endpoint: the source waited for the sink response, HTTP 200 completed successfully, and HTTP 400 produced an upstream failure. I also checked the outgoing query parameters for both settings.

Please don't hesitate to followup in this thread if you have further questions.