Re: Sync replication + high latency server

On 08/13/2015 07:41 AM, Edson Richter wrote:
>
> Em 13/08/2015 00:40, Joshua D. Drake escreveu:
>>
>> On 08/12/2015 05:33 PM, Edson Richter wrote:
>>> Hi!
>>>
>>> I've a situation where I would like to keep sync replication, where
>>> servers have 10Mbps network connection but high latency (normally, ~20ms
>>> but sometimes, 1000ms~2000ms, even 3000ms when network is under load).
>>>
>>> Considering that I will keep enough WAL files (let's say, 200 WAL
>>> segments on a server with low write rate):
>>>
>>> What happens if I configure timeout in master server for, let's say, 10
>>> seconds?
>>> Will sync replication survive if timeout happens, and then, network
>>> "recover" it self?
>>
>> I think you are misunderstanding how sync rep works.
>
> I don't think so: sync replication will force commit on both databases
> before returning OK to my app server.
>
>>
>>>
>>> Or will I be obligated to use async replication in such scenario?
>>>
>>
>> async is your friend here.
>
> And what about the timeout when using sync replication? What will happen?

If you are talking about archive_timeout, all that is going to do is
generate more WAL files. More to the point the WAL files will still the
same length(by default 16MB). So I am not sure how that is going to help
with your network issues.

If you are not talking about the above, then what timeout are referring to?

>
> Thanks,
>
> Edson
>
>
>>
>> JD
>>
>>
>
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com