On Tue, Apr 5, 2022 at 9:23 PM Bharath Rupireddy
<bharath.rupireddyforpostg...@gmail.com> wrote:
>
> Hi,
>
> I'm thinking if there's a way in core postgres to achieve $subject. In
> reality, the sync/async standbys can either be closer/farther (which
> means sync/async standbys can receive WAL at different times) to
> primary, especially in cloud HA environments with primary in one
> Availability Zone(AZ)/Region and standbys in different AZs/Regions.
> $subject may not be possible on dev systems (say, for testing some HA
> features) unless we can inject a delay in WAL senders before sending
> WAL.
>
> How about having two developer-only GUCs {async,
> sync}_wal_sender_delay? When set, the async and sync WAL senders will
> delay sending WAL by {async, sync}_wal_sender_delay
> milliseconds/seconds? Although, I can't think of any immediate use, it
> will be useful someday IMO, say for features like [1], if it gets in.
> With this set of GUCs, one can even add core regression tests for HA
> features.
>
> Thoughts?I think this is a common problem, people run into. Once way to simulate network delay is what you suggest, yes. But I was wondering if there are tools/libraries that can help us to do that. Googling gives OS specific tools but nothing like a C or perl library which can be used for this purpose. -- Best Wishes, Ashutosh Bapat
