[FIXED] (2.11) Deterministic clustered dedupe #6415
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Signed-off-by: Maurice van Veen <github@mauricevanveen.com>
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Issue description: - Publish a message with a `Nats-Msg-Id`. - Leader election through restarts/networking/etc. - Due to leader election the proposal queue is drained and the message is not stored/proposed. - Any retries of the original message will fail until the de-dupe window clears the original message, even though it was not stored in the stream. This issue is due to staging a zero sequence in the de-dupe map. An easy solution seems to clear all zero sequence entries from the de-dupe map upon stepping down, but that has correctness issues if any of those messages did get proposed. This PR removes the staging of a zero sequence and ensures all replicas can deterministically do de-duping themselves. And duplicate messages are only blocked at the cluster-level if we know what the sequence is. Signed-off-by: Maurice van Veen <github@mauricevanveen.com>
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Since the introduction of #6415 we have a deterministic way of de-duplication such that leader changes are no issue as well as never returning a zero-sequence or duplicate conflict error. However, during an upgrade this could result in stream desync. This was due to a replica accepting anything the leader tells it to do, ignoring if the message is a duplicate. So if the leader running the new version would propose multiple duplicate messages (which is correct under the new behavior), the old version would ingest all messages instead of only the first. This PR fixes that by having the leader only do these types of proposals if all servers within the group support it. Otherwise it falls back to the previous implementation. Signed-off-by: Maurice van Veen <github@mauricevanveen.com>
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Reverts #6415 and #6426. If duplication would be deferred to be done by a replica, and that replica was down for at least 'dupe window+5s', and it would clean up the dedupe map. A message that was meant to be duplicate could be passed as a genuine message, resulting in stream desync. Instead, the dedupe map should be cleared of any staged zero-sequences. However, that was not possible before as a new leader would not always be fully up-to-date when it starts responding to new write requests, which could result in duplicate messages as well. However, relying on the 'Leader Completeness Property' implemented here: #6485, we can confidently clear the dedupe map now of any staged zero-sequences (knowing they were not proposed). Ensuring both there's no desync, and a failed proposal for a message would not block subsequent messages with the same dedupe ID. Have left the commits as separate, to ease reviewing. Signed-off-by: Maurice van Veen <github@mauricevanveen.com>
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Issue description:
Nats-Msg-Id.This issue is due to staging a zero sequence in the de-dupe map. An easy solution seems to clear all zero sequence entries from the de-dupe map upon stepping down, but that has correctness issues if any of those messages did get proposed.
This PR removes the staging of a zero sequence and ensures all replicas can deterministically do de-duping themselves. And duplicate messages are only blocked at the cluster-level if we know what the sequence is.
Signed-off-by: Maurice van Veen github@mauricevanveen.com