Re: Why PostgreSQL doesn't implement a semi sync replication?

On 11/11/16 16:03, Francisco Olarte wrote:
> On Fri, Nov 11, 2016 at 4:40 AM, 余森彬  wrote:
>>     As we know, the synchronous commit process is blocked while receives
>> from acknowledgement from standby in
>> PostgreSQL.This is good for data consistence in master and standby, and
>> application can get important data from standby.But
>> when the standby crash or network goes wrong, the master could be hang.Is
>> there a feature plan for a semi sync like MySQL
>> InnoDB(set a timer, and become asynchronous when timeout)?
> 
> JMO, but it seems this basically means any process should be dessigned
> to cope with the posibility of not having replicated data after
> commit, so, why bother with synchronous replication in the first
> place?

It's often more acceptable to say "we lose data when 2 servers die (or
are in problems)" than "we lose data when 1 server dies" and it's also
more acceptable to say "we stop answering when we lose 2 servers" but
not "we stop answering when we lose 1 server", and semisync replication
works for combination of these two.

--  Petr Jelinek                  http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services