Hi folks, we've been running into a problem where multiple
replications with the same source and target are running
simultaneously. This introduces quite a lot of unnecessary network
traffic and causes real problems with update collisions on the local
replication history documents. If replicator A updates the source doc
and replicator B updates the target doc, subsequent replications will
decide that a full replication is necessary.
I have some ideas about how to ensure only one is running at a time
(more on that in a separate mail), but I'd like some feedback on how
to handle the second..Nth request. Let's call the initial POST to
_replicate "A" and the second POST "B":
Option 1 -- Respond to B with the results from A
This option works fine if the source is remote. However, if the
source is local, the replication started by A will be missing updates
to the source DB that occurred between A and B. B may be surprised by
that result.
Option 2 -- Grab an updated DB and continue the replication
This option will include updates to the source that occurred between A
and B in the response to both requests.
Option 3 -- Respond to A, then trigger another replication for B
In this case we wait till the replication started by A has completed,
then do an incremental one and respond to B with the results of that
incremental.
I think I'd vote for 3. Cheers, Adam
