From: | Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com> |
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To: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | How to simulate sync/async standbys being closer/farther (network distance) to primary in core postgres? |
Date: | 2022-04-05 15:53:24 |
Message-ID: | CALj2ACXtTSoPwmUx8NfwPzDf=jF9ZzZ36oRctHNps-YbUJ-NWA@mail.gmail.com |
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Lists: | pgsql-hackers |
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?
Regards,
Bharath Rupireddy.
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