Hi Andreas,
with continuous replications and an ever changing dataset there is no point
where you can tell your replication is "up-to-date" in terms of "100%
replicated" as replication always happens after the data has been written to
the source database. (which is a good thing)
You need to change the way you measure the up-to-date-ness. Instead of
measuring the percentage of completion you should better me sure the lag of
changes. e.g. targetDB is N changes behind sourceDB.
With couchdb 1.2 you get this number with a single request to /_active_tasks by
calculating a replications "source_seq" - "checkpointed_source_seq". Prior to
1.2 you can get this number too but its a more difficult because you have to
know the replications _local ID and check the "source_last_seq" field in the
replications session document…
Once you have the "lag of changes" for your continuous replications its a good
thing to graph it with some monitoring tool to get a big picture of how
replication performance is going through the day.
- mathias
On Jul 12, 2012, at 1:31 , Andreas Kemkes wrote:
> I wanted to follow up on this thread as I'm still experience difficulties
> using the feature and would like some advise how to best deal with the
> situation.
>
> The goal is to break up a monolithic database into multiple, which was
> achieved after a lot of trial and error. Now the quest is to keep it in sync
> for a while by using filtered, continuous replications. Yet the replication
> gets stuck on the last sequence number that passes the filter. In the Futon
> UI, I see:
>
> Checkpointed source sequence 165850, current source sequence 166253, progress
> 99%
>
> If I start a non-continuous replication with the exact same parameters, it
> returns:
>
>
> {
> "ok": true,
> "no_changes": true,
> "session_id": ...,
> "source_last_seq": 165850,
> "replication_id_version": 2,
> ...
> }
> It apparently knows that there are no changes and it knows the current source
> sequence. Why could it not move the checkpointed source sequence forward to
> match the current source sequence? What am I missing?
>
> Unless there is an exact match between checkpointed and current source
> sequence, how would one ever know if a replication is up-to-date?
>
> -- Andreas
>
>
> ________________________________
> From: Filipe David Manana <[email protected]>
> To: [email protected]; Andreas Kemkes <[email protected]>
> Sent: Thursday, June 21, 2012 12:40 PM
> Subject: Re: Replication and checkpoints - what to expect?
>
>> The same should be true for filtered replications if there is no applicable
>> document between the current source sequence and the last checkpoint.
>> Otherwise you would be always wondering if it has been replicated entirely.
>
> That's harder. With filtered replication, we only know about sequence
> numbers of changes that pass the filter.
