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1. Generate a correct producer snapshot prior to upload - we rejected this because we either have to reply the log from the beginning or choose an arbitrary earlier segment as the starting point to start calculating said snapshot from.
2. Make Kafka not upload segments to remote storage until it has expired all segments lacking a producer snapshot - we think this is just as unexpected (especially if customers aren't well-aware of what producer snapshots are used for) as what the current approach is.
3. Do not allow a topic to have its tiering configuration set to true until all of its segments have an associated producer snapshot - the limitation here is that this condition needs to hold true across all brokers and additional synchronisation will be requiredI cannot think of downsides to this alternative.
4. Do not archive snapshot files - like indices, snapshot files can be recreated by rereading the log. However, in the case of Tiered Storage we make the assumption that replaying the whole log will be quite costly.
5. Create empty snapshot files on read if a snapshot file is not found - this is a close second runner, but we chose to discard it . It would not be immediately obvious whether a snapshot is not presented because of an upgrade of Kafka version, because there is a bug in the plugin implementation or because the remote storage itself has been tampered with - if we explicitly write an empty file we reduce some of this ambiguity.