Make Translog an implementation detail of an Engine instead of required

[dakrone]

This is a followup to #31220 (comment) where it would be nice if we could make the abstract Engine class not expose information that made it seem like it has a Translog. This would include functions with Translog in the name, as well as perhaps using return values that aren't sub classes of Translog.

It would be nice if an engine consumer could use an engine without having to know about translog implementation details (or without the presence of a translog, if desired).

[elasticmachine]

Pinging @elastic/es-distributed

[dakrone]

Here's an initial list that would need renaming, removing, or reorganizing

• isTranslogSyncNeeded -> isSyncNeeded
• syncTranslog -> sync
• ensureTranslogSynced -> ensureSynced
• acquireTranslogRetentionLock -> acquireRetentionLock
• newTranslogSnapshotFromMinSeqNo -> newSnapshotFromMinSeqNo
• estimateTranslogOperationsFromMinSeq -> estimateOperationsFromMinSeq
• getTranslogStats -> getStats
• getTranslogLastWriteLocation -> getLastWriteLocation

Additionally, if we wanted to do this we'd have to have generic return values and eschew our use of Translog.Snapshot and Translog.Location

[jasontedor]

I don't think this issue should be about renaming these methods but rather removing their need to be on the Engine public API? These methods simply do not make sense without translog in the name if they are doing something to the translog.

[dakrone]

I agree, we don't have to keep all the methods, I editing the comment to say "renaming, removing, or reorganizing"

[ywelsch]

@dakrone Can this be closed now with #31220 merged?

[dakrone]

I think this can be closed now.