Re: Changing the setting of wal_sender_timeout per standby

On Thu, Sep 13, 2018 at 12:32 PM, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> On Thu, Sep 13, 2018 at 01:14:12AM +0000, Tsunakawa, Takayuki wrote:
>> Some customer wants to change the setting per standby, i.e., a shorter
>> timeout for a standby in the same region to enable faster detection
>> failure and failover, and a longer timeout for a standby in the remote
>> region (for disaster recovery) to avoid mis-judging its health.
>
> This argument is sensible.
>
>> The current PGC_HUP allows to change the setting by editing
>> postgresql.conf or ALTER SYSTEM and then sending SIGHUP to a specific
>> walsender. But that's not easy to use. The user has to do it upon
>> every switchover and failover.
>>
>> With PGC_BACKEND, the user would be able to tune the timeout as follows:
>>
>> [recovery.conf]
>> primary_conninfo = '... options=''-c wal_sender_timeout=60000'' ...'
>>
>> With PGC_USERSET, the user would be able to use different user
>> accounts for each standby, and tune the setting as follows:
>>
>> ALTER USER repluser_remote SET wal_sender_timeout = 60000;
>
> It seems to me that switching to PGC_BACKENDwould cover already all the
> use-cases you are mentioning, as at the end one would just want to
> adjust the WAL sender timeout on a connection basis depending on the
> geographical location of the receiver and the latency between primary
> and standby.

+1 for PGC_BACKEND. It looks enough for most use cases.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center