You are viewing a plain text version of this content. The canonical link for it is here.
Posted to notifications@couchdb.apache.org by "nickva (via GitHub)" <gi...@apache.org> on 2026/01/26 18:27:12 UTC
[I] [ENHANCEMENT]: Improve the behavior of replication since_seq parameter [couchdb]
nickva opened a new issue, #5867:
URL: https://github.com/apache/couchdb/issues/5867
### Provide a brief overview of what the new feature is all about
Currently the `since_seq` replication parameter forces a replication job to start from the given `since_seq` sequence ignoring the checkpoints. That's its intended behavior but it only works well until the first time the replication checkpoints. After it checkpoints, and the job restarts, those later checkpoints will be ignored and the job will again restart from since_seq. So a job with a since_seq parameter will always replay the whole changes feed since the starting `since_seq` parameter, and what's worse, clobber and rewind the replication checkpoints in the process as well.
### Tell us how the new feature should work. Be specific
A better behavior might be to check the pending changes count with the checkpointed sequence (or 0 if there are none) and the since_seq, and use the one which has fewer pending changes. This way if a user sets and forgets a since_seq, the replication will start from the since_seq value they set if that's later than the last checkpointed sequence. Replication will then make some progress and make new checkpoints and later start using those newer checkpoints.
If a user really wants to reset the replication back they can still do it, by deleting the replication checkpoints on both source and target, and set an arbitrary since_seq. On startup since the replication checkpoints were reset they will have the largest pending count so since_seq will be used.
### Not required. Suggest how to implement the addition or change
_No response_
### Additional Context
_No response_
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: notifications-unsubscribe@couchdb.apache.org.apache.org
For queries about this service, please contact Infrastructure at:
users@infra.apache.org
Re: [I] [ENHANCEMENT]: Improve the behavior of replication since_seq parameter [couchdb]
Posted by "rnewson (via GitHub)" <gi...@apache.org>.
rnewson commented on issue #5867:
URL: https://github.com/apache/couchdb/issues/5867#issuecomment-3805931540
Not keen on the behaviour varying by the somewhat flaky pending changes runtime calculation, and there's a backward compatibility issue. That said, using since_seq is quite rare, and only advised for very niche cases (cluster migration, essentially).
It would perhaps be better that we simply honour a replication checkpoint even if since_seq is set. the replication checkpoint should supercede the since_seq value (it's a "replication that started at this seq" not "a replication that must always start at this seq"). Which for safety means the since_seq value has to be included in the replication hash (its presence means it's a different replication from one that is identical in all properties except it lacks since_seq).
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: notifications-unsubscribe@couchdb.apache.org
For queries about this service, please contact Infrastructure at:
users@infra.apache.org
Re: [I] [ENHANCEMENT]: Improve the behavior of replication since_seq parameter [couchdb]
Posted by "nickva (via GitHub)" <gi...@apache.org>.
nickva commented on issue #5867:
URL: https://github.com/apache/couchdb/issues/5867#issuecomment-3807098962
> and there's a backward compatibility issue.
I think both proposal would be a compatibility issue. But it also feels more a bug fix. The replication always restarting from the since_seq parameter and overwriting the checkpoints again seems broken and not useful or intuitive.
> the replication checkpoint should supercede the since_seq value (it's a "replication that started at this seq" not "a replication that must always start at this seq"). Which for safety means the since_seq value has to be included in the replication hash (its presence means it's a different replication from one that is identical in all properties except it lacks since_seq).
Hmm, that would be a better, more thorough, fix I think. It might preclude some `since_seq` uses, say as a way to fast-forward an existing replication temporarily and since it changes the replication checkpoints IDs, it would be a larger compatibility issue. But if it makes the parameter behavior more consistent and predictable, I'd be for it.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: notifications-unsubscribe@couchdb.apache.org
For queries about this service, please contact Infrastructure at:
users@infra.apache.org
Re: [I] [ENHANCEMENT]: Improve the behavior of replication since_seq parameter [couchdb]
Posted by "jiahuili430 (via GitHub)" <gi...@apache.org>.
jiahuili430 commented on issue #5867:
URL: https://github.com/apache/couchdb/issues/5867#issuecomment-3899361236
Fixed by PR https://github.com/apache/couchdb/pull/5881.
Thanks to Robert for his brilliant idea, and also to Nick for his guidance and
concise initial code, which made expansion and maintenance much easier!
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: notifications-unsubscribe@couchdb.apache.org
For queries about this service, please contact Infrastructure at:
users@infra.apache.org
Re: [I] [ENHANCEMENT]: Improve the behavior of replication since_seq parameter [couchdb]
Posted by "jiahuili430 (via GitHub)" <gi...@apache.org>.
jiahuili430 closed issue #5867: [ENHANCEMENT]: Improve the behavior of replication since_seq parameter
URL: https://github.com/apache/couchdb/issues/5867
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: notifications-unsubscribe@couchdb.apache.org
For queries about this service, please contact Infrastructure at:
users@infra.apache.org