Rewind when messages appear behind offset #496
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Signed-off-by: Peter Broadhurst <peter.broadhurst@kaleido.io>
awrichar
reviewed
Feb 8, 2022
internal/batch/batch_manager.go
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| func (bm *batchManager) markRewind(rewindTo int64) { | ||
| bm.rewindMux.Lock() | ||
| bm.rewindTo = rewindTo |
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Should we check if rewindTo is already set?
awrichar
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Feb 8, 2022
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awrichar
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awrichar
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Marked one item that I think requires a change.
Signed-off-by: Peter Broadhurst <peter.broadhurst@kaleido.io>
awrichar
approved these changes
Feb 8, 2022
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Fix for #493
Observed reviewing the logs for #493 that the messages were never being picked up by the batch processor, and the perf tool is submitting them in a highly parallel way. My analysis is that with PSQL as used in this test (or any production ready database) parallel writing of messages to the DB could result in the commit order of the transactions, being mismatched with the sequence allocation to the rows.
The code in the batch manager did not handle this - it would simply do a shoulder tap to re-read from the DB when a message was created, but not check if that message had appeared behind the offset and it needed to do a rewind.
This code change implements a simple rewind (like we have for the event aggregator).
Note this means that in the case of parallel REST API submission of messages, the final delivery order might not match the local sequence order. However, that's in-line with the assurances FireFly provides - as application should only be able to depend on.