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From Jan Van Besien <ja...@ngdata.com>
Subject Re: HBase replication: "in order semantics"
Date Fri, 16 Nov 2012 11:18:52 GMT
On 11/15/2012 06:45 PM, lars hofhansl wrote:
> Yes. If there are failures in the source cluster the replicated data might be delivered
out of order.

ok.

> Note that you will never see partial rows applied; replication will enforce HBase's ACID
guarantee here,

ok.

> but rows might be delivered out of order, which means the ordering of deletes and puts
might change, and hence lead to *temporary* visibility of deleted data. Eventually the state
will be correct, though.

I understand that there are situations in which the reordering results 
in temporary visibility of deleted data. But additionally I also think 
that there are (unlikely) situations which can lead to permanent 
visibility of deleted data on the replica.

The situation I think of is:
- put followed by delete on source cluster
- reordering resulting in delete followed by put on replica
- delete gets executed on replica
- a major compaction happens on the replica (thus "really" deleting)
- put gets executed on the replica (thus permanently staying there)

Is there an error in my reasoning?

thanks,
Jan


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