jsancio commented on code in PR #15671:
URL: https://github.com/apache/kafka/pull/15671#discussion_r1586526016
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raft/src/main/java/org/apache/kafka/raft/ReplicatedLog.java:
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@@ -261,7 +260,7 @@ default long truncateToEndOffset(OffsetAndEpoch endOffset) {
* @param snapshotId the end offset and epoch that identifies the snapshot
* @return a writable snapshot if it doesn't already exist
*/
- Optional<RawSnapshotWriter> storeSnapshot(OffsetAndEpoch snapshotId);
+ Optional<RawSnapshotWriter> createNewSnapshotUnchecked(OffsetAndEpoch
snapshotId);
Review Comment:
So the use cases are very different hence the reason why I separated the
methods.
`createNewSnapshot` is indirectly called by the KRaft state machine. In this
case the `ReplicatedLog` makes sure that the provided snapshot id (offset and
epoch) is consistent with the log.
`createNewSnapshotUnchecked` is used by the local replica to override the
entire log with the leader's snapshot. For example, right after downloading the
snapshot we fully truncate the log:
https://github.com/apache/kafka/blob/trunk/raft/src/main/java/org/apache/kafka/raft/KafkaRaftClient.java#L1459-L1473
This part of the code calls `truncateToLatestSnapshot` which deletes all of
the old snapshots and replaces the log with an empty log that start at the just
downloaded snapshot (the latest snapshot). In other words
`truncateToLatestSnapshot` makes the `ReplicadLog` consistent after the direct
use of `createNewSnapshotUnchecked`.
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