Re: Synchronizing slots from primary to standby

On Thu, Dec 7, 2023 at 2:57 PM Drouvot, Bertrand
<bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> Hi,
>
> On 12/7/23 10:07 AM, shveta malik wrote:
> > On Thu, Dec 7, 2023 at 1:19 PM Drouvot, Bertrand
> > <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> >> Might be worth to add comments in the code (around the WalRcv->latestWalEnd
> >> checks) that no "lagging" sync are possible if the walreceiver is not started
> >> though?
> >>
> >
> > I am a bit confused. Do you mean as a TODO item? Otherwise the comment
> > will be opposite of the code we are writing.
>
> Sorry for the confusion: what I meant to say is that
> synchronization (should it be lagging) is not possible if the walreceiver is not started
> (as XLogRecPtrIsInvalid(WalRcv->latestWalEnd) would be true).
>

Sure, I will add it. Thanks for the clarification.

> More precisely here (in synchronize_slots()):
>
> /* The primary_slot_name is not set yet or WALs not received yet */
> SpinLockAcquire(&WalRcv->mutex);
> if (!WalRcv ||
> (WalRcv->slotname[0] == '\0') ||
> XLogRecPtrIsInvalid(WalRcv->latestWalEnd))
> {
> SpinLockRelease(&WalRcv->mutex);
> return naptime;
> }
>
> Regards,
>
> --
> Bertrand Drouvot
> PostgreSQL Contributors Team
> RDS Open Source Databases
> Amazon Web Services: https://aws.amazon.com