Exactly-Once Semantics (EOS)

Exactly-Once Semantics (EOS) is the strongest processing guarantee in stream processing, ensuring that each input event's effect on the system's state is recorded precisely once, even amidst failures and retries. Achieving true end-to-end EOS often involves coordination between the stream processor (like RisingWave, which provides EOS for its internal state) and the source/sink connectors using mechanisms like transactions or idempotent writes.