XDCR replication couchbase 4.0


#1

I am using the couchbase 4.0, just would like to insights of xdcr. how data is being replicated.

  1. what is the maximum size/count for queue to hold the documents in xdcr queue?
  2. is it configurable ?
  3. is mutations storage in xdcr queue are persisted?
  4. if node failed with having pending mutation(source cluster node) to destination cluster, will it cause loss of mutations?

#2

you can find of the details here: http://developer.couchbase.com/documentation/server/4.1/architecture/cross-datacenter-replication.html

Unlike some relational replication schemes, XDCR does not maintain some queue that fills up. The destination can be unavailable for long periods of time (months) and XDCR will continue to retry replication but won’t impact the mutation on the source cluster. This is also true for DCP which is the underlying replication protocol for intra cluster replication as well as XDCR


#3

Thanks cihangirb for the reply. what is the underlying storage for this XDCR outbounding queue messages. also replication queue.


#4

replication is done with timestamps and there is a way for replication to retrieve updates after a given timestamp without managing a queue that is significant in size. So when you fall behind with DCP or XDCR, if we cannot find the updates for a given timestamp in memory, we can go to disk and retrieve these items. So there is no large replication queue per say. The “queues” for replication are in memory.

thanks
-cihan


#5

Thanks cihangirb, i believe this would apply to replica copies as well.


#6

Yes, that is correct it applies for XDCR and (internal) DCP replication.

Anil Kumar