From: | Francisco Olarte <folarte(at)peoplecall(dot)com> |
---|---|
To: | Sébastien Lorion <sl(at)thestrangefactory(dot)com> |
Cc: | Keith Fiske <keith(at)omniti(dot)com>, Kevin Goess <kgoess(at)bepress(dot)com>, PostgreSQL <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Merge a sharded master into a single read-only slave |
Date: | 2014-06-05 16:55:41 |
Message-ID: | CA+bJJbxkJDMh+vKofFvQ07MLJLtDySiXqDTVuzVLv=Pi_BQoSQ@mail.gmail.com |
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Lists: | pgsql-general |
Hi Sébastien:
On Thu, Jun 5, 2014 at 5:41 PM, Sébastien Lorion
<sl(at)thestrangefactory(dot)com> wrote:
> .... Correct me if I am wrong, but will it not also suffer the same
> limitation as any statement based replication, namely that the "merged"
> slave will have to sustain the same write load as all shards combined ?
I cannot tell you the exact mimeo behaviour, but if you incremental
replication using an id/timestamp by >pulling< changes from the
masters, you will normally batch them and insert all the changes to
the slaves in a single transaction, which leads to less load as many
times your limit is in transaction rate, not record rate. (i.e., every
5 minutes you query for all the tuples changed, and insert/update them
all in one go ) ( Also, if tuples are updated many times between
sweeps the slave will get only one )
Francisco Olarte.
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