Hi,
On 9/19/23 6:50 AM, shveta malik wrote:
On Wed, Sep 13, 2023 at 5:19 PM Amit Kapila <amit.kapil...@gmail.com> wrote:
On Wed, Sep 13, 2023 at 4:54 PM shveta malik <shveta.ma...@gmail.com> wrote:
PFA v17. It has below changes:
@@ -2498,6 +2500,13 @@ ReorderBufferProcessTXN(ReorderBuffer *rb,
ReorderBufferTXN *txn,
}
else
{
+ /*
+ * Before we send out the last set of changes to logical decoding
+ * output plugin, wait for specified streaming replication standby
+ * servers (if any) to confirm receipt of WAL upto commit_lsn.
+ */
+ WaitForStandbyLSN(commit_lsn);
It seems the first patch has a wait logic for every commit. I think it
is better to integrate this wait with WalSndWaitForWal() as suggested
by Andres in his email[1].
[1] -
https://www.postgresql.org/message-id/20220207204557.74mgbhowydjco4mh%40alap3.anarazel.de
--
Sure Amit. PFA v18. It addresses below:
1) patch001: wait for physical-standby confirmation logic is now
integrated with WalSndWaitForWal(). Now walsender waits for physical
standby's confirmation to take changes upto RecentFlushPtr in
WalSndWaitForWal(). This allows walsender to send the changes to
logical subscribers one by one which are already covered in
RecentFlushPtr without needing to wait on every commit for physical
standby confirmation.
+ /* XXX: Is waiting for 1 second before retrying enough or more or less?
*/
+ (void) WaitLatch(MyLatch,
+ WL_LATCH_SET | WL_TIMEOUT |
WL_EXIT_ON_PM_DEATH,
+ 1000L,
+
WAIT_EVENT_WAL_SENDER_WAIT_FOR_STANDBY_CONFIRMATION);
I think it would be better to let the physical walsender(s) wake up those
logical
walsender(s) (instead of waiting for 1 sec or such). Maybe we could introduce a
new CV that would
broadcast in PhysicalConfirmReceivedLocation() when restart_lsn is changed,
what do you think?
Still regarding preventing the logical replication to go ahead of
physical replication standbys specified in standby_slot_names: we currently
don't impose this
limitation to pg_logical_slot_get_changes and friends (that don't start a
dedicated walsender).
Shouldn't we also prevent them to go ahead of physical replication standbys
specified in standby_slot_names?
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
