Simon,
On Mon, Apr 8, 2013 at 7:14 PM, Simon Majou <si...@majou.org> wrote: > Hello, > > I want to sync a bucket of a first cluster with the bucket of a second > cluster. To do that I think using the post commit hook. > If you didn't know, this is exactly what Riak Enterprise was built to do. I.e. handle multi-cluster replication. However, if you want to give it a go on your own a post-commit hook is one way to get the job done. You'll want to think through failure scenarios where the receiving cluster is down and how to deal with msgs that are dropped between clusters. The post-commit hook runs on a process called the "coordinator", there is a coordinator for every incoming request. So you won't block the vnodes, which is important, but the client/user request will block until your post-commit returns. > > Is there any risk that the sequence of PUTs to be mixed in such a scenario > ? > Do you mean the sequence seen on cluster A vs. cluster B? Are you asking if the object could appear to be on B before A even though the PUT was sent to A? The answer is, it depends. With a healthy system it's probably unlikely but it will depend on your DW values and state of each cluster. E.g. if cluster A nodes get slow disk I/O then perhaps the replication to cluster B could beat writes on A. If we start introducing node and network failures, or changing W/DW values then things can get more complicated. You could have success on cluster A, fire replica to cluster B, all primary nodes for that object on cluster A die, now cluster B will have a key for which cluster A says not_found (well, not totally true, depends on your PR value). -Z
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