[pgpool-general: 6121] Re: Confused between Running Modes !

[Nitish Kumar]

Thanks for such a prompt reply Sir !

Yeah I am sorry I framed my question incorrectly. Actually I wanted the difference between PgPool II 3.7.3 "replication" mode & "master-slave" mode.
Anyways from your reply its clear that if PostgreSQL Server's are doing actual replication then PgPool II 3.7.3 should be set up in master-slave mode with
sub-mode of "stream" with load - balancing on. Right ????

In that case PgPool II will smartly load-balance queries based on its type to slave or master. PgPool will not do any replication.

Glad to get such a prompt response. Still If I am getting anything wrong do let me know.

Regards,
Nitish Kumar

On 06/08/18 04:39 PM, Tatsuo Ishii  <ishii at sraoss.co.jp> wrote: 
> 
> > Hi Team,
> > 
> > Kindly guide me ! I am heavily confused between Running modes of PgPool II 3.7.3.
> > 
> > I am having 3 PostgreSQL 10 Servers running in Streaming replication Hot Standby mode. In which 1 is master and 2 are slaves. 
> > The 1 master PostgreSQL 10 Server supports both read/write and 2 slave PostgreSQL 10 Servers supports only read queries.
> > 
> > I am setting PgPool II 3.7.3 to load balance all my queries among these 3 servers based on query type i.e read queries should be distributed between
> > all the 3 PostgreSQL 10 servers and write query should only go to Master PostgreSQL 10 server. I don't want PgPool to do replication ! I just want PgPool to
> > do smart load-balancing. 
> > 
> > Now for this above configuration of mine I am not able to decide PgPool II 3.7.3. Running Modes. I am confused between Master-Slave(Stream) Mode 
> > and Streaming Replication mode !
> > 
> > Since the documentation for both the modes suggests that the streaming/replication and synchronization of data will be done by PostgreSQL 10 servers.
> > 
> > Please elaborate any technical details of both the modes if I am missing anything. And most importantly considering my PostgreSQL 10 Servers infrastructure 
> > which mode should I use ???
> > 
> > I may missing something. Any suggestions are welcome.
> > 
> > Regards,
> > Nitish Kumar
> 
> > I am confused between Master-Slave(Stream) Mode and Streaming Replication mode !
> 
> Actually they are identical, meaning:
> 
> master_slave_mode = on
> master_slave_sub_mode = 'stream'
> 
> In this mode replication are done by PostgreSQL. Pgpool-II does load
> balancing.
> 
> Some background of this:
> 
> In the early days of Pgpool-II, there was only master_slave_mode,
> which supposed to use Slony-I, since streaming replication did not
> exist yet. Then the streaming replication comes up. From a Pgpool-II's
> point of veiw, there were subtle differences in the way to handle
> Slony-I and streaming replication. So we invented
> master_slave_sub_mode to distinguish them.
> 
> > Please elaborate any technical details of both the modes if I am missing anything. And most importantly considering my PostgreSQL 10 Servers infrastructure 
> > which mode should I use ???
> 
> I think for most uses cases streaming replication mode should be best
> for you. However if your application is sensitive to replication
> delay between PostgreSQL primary and standby, you might want to set
> synchronous_commit = remote_apply in postgresql.conf, which eliminate
> the replication delay sacrificing performance. Because primary has to
> wait before commit until standby applies the WAL.
> 
> Best regards,
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese:http://www.sraoss.co.jp
> 
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