Re: Libpq support to connect to standby server as priority

>> I'm confused as to how this would work. Who or what determines if the server
>> is a primary or standby?
> 
> Overall, the server determines the server role (primary or standby) using the same mechanism as pg_is_in_recovery(),
andset the server_role GUC parameter.  As the parameter is GUC_REPORT, the change is reported to the clients using the
ParameterStatus('S') message.  The clients also get the value at connection.
 

But pg_is_in_recovery() returns true even for a promoting standby. So
you have to wait and retry to send pg_is_in_recovery() until it
finishes the promotion to find out it is now a primary. I am not sure
if backend out to be responsible for this process. If not, libpq would
need to handle it but I doubt it would be possible.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
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