Re: Synchronizing slots from primary to standby

Hi,

On Thu, Feb 15, 2024 at 06:13:38PM +0530, Amit Kapila wrote:
> On Thu, Feb 15, 2024 at 12:07 PM Zhijie Hou (Fujitsu)
> <houzj(dot)fnst(at)fujitsu(dot)com> wrote:
> >
> > Since the slotsync function is committed, I rebased remaining patches.
> > And here is the V88 patch set.
> >

Thanks!

>
> Please find the improvements in some of the comments in v88_0001*
> attached. Kindly include these in next version, if you are okay with
> it.

Looking at v88_0001, random comments:

1 ===

Commit message "Be enabling slot synchronization"

Typo? s:Be/By

2 ===

+ It enables a physical standby to synchronize logical failover slots
+ from the primary server so that logical subscribers are not blocked
+ after failover.

Not sure "not blocked" is the right wording.
"can be resumed from the new primary" maybe? (was discussed in [1])

3 ===

+#define SlotSyncWorkerAllowed() \
+ (sync_replication_slots && pmState == PM_HOT_STANDBY && \
+ SlotSyncWorkerCanRestart())

Maybe add a comment above the macro explaining the logic?

4 ===

+#include "replication/walreceiver.h"
#include "replication/slotsync.h"

should be reverse order?

5 ===

+ if (SlotSyncWorker->syncing)
{
- SpinLockRelease(&SlotSyncCtx->mutex);
+ SpinLockRelease(&SlotSyncWorker->mutex);
ereport(ERROR,
errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("cannot synchronize replication slots concurrently"));
}

worth to add a test in 040_standby_failover_slots_sync.pl for it?

6 ===

+static void
+slotsync_reread_config(bool restart)
+{

worth to add test(s) in 040_standby_failover_slots_sync.pl for it?

[1]: https://www.postgresql.org/message-id/CAA4eK1JcBG6TJ3o5iUd4z0BuTbciLV3dK4aKgb7OgrNGoLcfSQ%40mail.gmail.com

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com