3 ms·
Physical at-least-once is easy to transform into a logical exactly-once. Just assign a unique id to every message at the source and discard duplicates at the ta
by pkolaczk 11y ago
Physical at-least-once is easy to transform into a logical exactly-once. Just assign a unique id to every message at the source and discard duplicates at the target.
- falcolas 11y agoYou're describing "at most once". The key is that a message could be lost between components, and there's nothing here which accounts for that. EDIT: To clarify a bit more, I'm looking at the "at most once" as once throughout the entire system. Not once per node. Combining a physical at-least-once with a logical "at-most-once" only works at the per-logical node level, not at the system level. Some processing will occur more than once in a system, which could have negative consequences if the processing is not strictly idempotent.
- TheHydroImpulse 11y agoUsing an acking system (like that in Storm or Heron) would move it to be physically at-least-once with a logical exactly-once by de-duping at the target. This means if you observe the inner system, you won't be seeing exactly-once semantics but looking at the system from the outside, the semantics would indeed be exactly-once at the target.