Ignore stale classic remoting ACKs (backport #3158 to 1.7.x)#3168
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Ignore stale classic remoting ACKs (backport #3158 to 1.7.x)#3168He-Pin wants to merge 1 commit into
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Stale system-message acknowledgements can arrive after classic remoting reconnects and the sender has reset its resend buffer for the current UID. Treating a cumulative ACK newer than the sender buffer as a protocol violation gates/quarantines an otherwise valid association. Modification: Make AckedSendBuffer ignore cumulative ACKs beyond the highest sequence number it has seen, log and skip those ACKs in ReliableDeliverySupervisor, and add regression coverage for empty/non-empty buffers, stale ACKs with NACKs, and valid ACK processing after a stale ACK. Result: Late ACKs from an old receive buffer no longer trigger HopelessAssociation/quarantine, while real unfulfillable NACKs still fail through the existing ResendUnfulfillableException path. Tests: - sbt "remote / Test / testOnly org.apache.pekko.remote.AckedDeliverySpec" / passed: 13 tests - sbt checkCodeStyle / passed - scalafmt --list --mode diff-ref=origin/main / passed: no files listed - git diff --check / passed: no output - subAgent review / FINAL PASS - qodercli review (non-interactive, log: /tmp/tmo-qoder-review.log) / PASS References: Fixes #3126
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Motivation
Backport of #3158 to 1.7.x.
Classic remoting can receive a delayed system-message ACK from an old association after reconnect/reset. If that stale ACK has a cumulative sequence number newer than the sender's current resend buffer, the old code treated it as a protocol violation, wrapped it as
HopelessAssociation, and gated/quarantined the remote system.See also: akka/akka-core#24654 (same bug in Akka, closed without fix in 2019).
Modification
Ack(cumulativeAck > maxSeq)as stale inAckedSendBufferand return the current buffer unchanged.ReliableDeliverySupervisorbefore they can be wrapped intoHopelessAssociation.ResendUnfulfillableExceptionpath for real unfulfillable NACKs.Result
Delayed ACKs from a previous association no longer trigger quarantine for the current association, while normal ACK/NACK processing remains unchanged.
Tests
sbt "remote / Test / testOnly org.apache.pekko.remote.AckedDeliverySpec"/ passed (main branch)References
Fixes #3126. Backport of #3158.