Re: Merge a sharded master into a single read-only slave

On Thu, Jun 5, 2014 at 2:09 PM, Sébastien Lorion <sl(at)thestrangefactory(dot)com>
wrote:

> On Thu, Jun 5, 2014 at 12:55 PM, Francisco Olarte <folarte(at)peoplecall(dot)com>
> wrote:
>
>> 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.
>>
>
> ​You are right, requesting changes at fixed time intervals would certainly
> help reduce the load. I will have to test and see if a good balance can be
> achieved between not having stale data for too long and keeping up with
> writes.
>
> Sébastien
>
>
If you have any questions while evaluating it, feel free to ask or post any
issues to github.

--
Keith Fiske
Database Administrator
OmniTI Computer Consulting, Inc.
http://www.keithf4.com