Re: Time delayed LR (WAS Re: logical replication restrictions)

On Thu, Feb 23, 2023 at 5:40 PM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
>
> Thank you for reviewing! PSA new version.
>

I was trying to think if there is any better way to implement the
newly added callback (WalSndDelay()) but couldn't find any. For
example, one idea I tried to evaluate is whether we can merge it with
the existing callback WalSndUpdateProgress() or maybe extract the part
other than progress tracking from that function into a new callback
and then try to reuse it here as well. Though there is some common
functionality like checking for timeout and processing replies still
they are different enough that they seem to need separate callbacks.
The prime purpose of a callback for the patch being discussed here is
to delay the xact before sending the commit/prepare whereas the
existing callback (WalSndUpdateProgress()) or what we are discussing
at [1] allows sending the keepalive message in some special cases
where there is no communication between walsender and walreceiver.
Now, the WalSndDelay() also tries to check for timeout and send
keepalive if necessary but there is also dependency on the delay
parameter, so don't think it is a good idea of trying to combine those
functionalities into one API.

Thoughts?

[1] - https://www.postgresql.org/message-id/20230210210423.r26ndnfmuifie4f6%40awork3.anarazel.de

--
With Regards,
Amit Kapila.