Horton

Re: Synchronizing slots from primary to standby

shveta malik <shveta.malik@gmail.com>

View thread View on postgr.es
From: shveta malik <shveta.malik@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Bruce Momjian <bruce@momjian.us>, Ashutosh Sharma <ashu.coek88@gmail.com>, Andres Freund <andres@anarazel.de>, pgsql-hackers <pgsql-hackers@postgresql.org>, Ajin Cherian <itsajin@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, shveta malik <shveta.malik@gmail.com>
Date: 2024-01-02T10:31:48Z
Lists: pgsql-hackers

Attachments

On Fri, Dec 29, 2023 at 10:25 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Fri, Dec 29, 2023 at 7:18 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > On Wed, Dec 27, 2023 at 7:13 PM shveta malik <shveta.malik@gmail.com> wrote:
> > >
> > > On Wed, Dec 27, 2023 at 11:36 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> >
> > >  I was not aware if there is any way to connect if we
> > > want to run SQL queries. I initially tried using 'PQconnectdbParams'
> > > but couldn't make it work. Perhaps it is to be used only by front-end
> > > and extensions as the header files indicate as well:
> > >  * libpq-fe.h :      This file contains definitions for structures and
> > >  externs for functions used by frontend postgres applications.
> > >  * libpq-be-fe-helpers.h:   Helper functions for using libpq in
> > > extensions . Code built directly into the backend is not allowed to
> > > link to libpq directly.
> >
> > Oh I didn't know that. Thank you for pointing it out.
> >
> > But I'm still concerned it could confuse users that
> > pg_stat_replication keeps showing one entry that remains as "startup"
> > state.

Okay. I understand your concern. I have attached PoC patch
(v55_02-0004) which attempts to implement non-replication connection
in slotsync worker. By doing so, pg_stat_replication will not show its
entry while pg_stat_activity will still show it with 'state' as either
"active" or "idle". Currently, since we are not using any of the
replication cmds, thus non-replication connection suits well. But in
future, if there is a requirement to execute existing (or new) cmd in
slotsync worker, then that can not be done simply in non-replication
connection; it will need some changes in non-replication  or will need
the replication connection itself.

>> It has the same application_name as the walreceiver uses. For
> > example, when users want to check the particular replication
> > connection, it's common to filter the entries by the application name.
> > But it will end up having duplicate entries having different states.
> >
>
> Valid point. The main reason for using cluster_name is that if
> multiple standby's connect to the same primary, all will have the same
> application_name as 'slotsyncworker'. The other alternative could be
> to use {cluster_name}_slotsyncworker, which will probably address your
> concern and we can have to provision to differentiate among
> slotsyncworkers from different standby's.

The topup patch has also changed app_name to
{cluster_name}_slotsyncworker so that we do not confuse between
walreceiver and slotsyncworker entry.

Please note that there is no change in rest of the patches, changes
are in additional 0004 patch alone.

> --
> With Regards,
> Amit Kapila.

Commits

  1. Doc: Add the new section "Logical Replication Failover".

  2. Fix the review comments and a bug in the slot sync code.

  3. Fix a test in failover slots regression test.

  4. Fix the intermittent buildfarm failures in 040_standby_failover_slots_sync.

  5. Split XLogCtl->LogwrtResult into separate struct members

  6. Ensure that the sync slots reach a consistent state after promotion without losing data.

  7. Introduce a new GUC 'standby_slot_names'.

  8. Fix BF failure introduced by commit b3f6b14cf4.

  9. Fixups for commit 93db6cbda0.

  10. Fix BF failure in commit 93db6cbda0.

  11. Add a new slot sync worker to synchronize logical slots.

  12. Improve ERROR/LOG messages added by commits ddd5f4f54a and 7a424ece48.

  13. Disable autovacuum on primary in 040_standby_failover_slots_sync test.

  14. Fix the incorrect format specifier used in commit 7a424ece48.

  15. Change the LOG level in 040_standby_failover_slots_sync.pl to DEBUG2.

  16. Add more LOG and DEBUG messages for slot synchronization.

  17. Another try to fix BF failure introduced in commit ddd5f4f54a.

  18. Fix BF introduced in commit ddd5f4f54a.

  19. Add a slot synchronization function.

  20. Clean-ups for 776621a5e4 and 7329240437.

  21. Enhance libpqrcv APIs to support slot synchronization.

  22. Add a failover option to subscriptions.

  23. Allow setting failover property in the replication command.

  24. Allow to enable failover property for replication slots via SQL API.

  25. Add macros for looping through a List without a ListCell.

  26. Track conflict_reason in pg_replication_slots.

  27. Allow upgrades to preserve the full subscription's state.

  28. Add support for incremental backup.

  29. Simplify some logic in CreateReplicationSlot()

  30. Fix uninitialized access to InitialRunningXacts during decoding after ERROR.

  31. Flexible options for CREATE_REPLICATION_SLOT.

  32. Empty search_path in logical replication apply worker and walsender.

  33. Fix oldest xmin and LSN computation across repslots after advancing

  34. Require C99 (and thus MSCV 2013 upwards).