Re: restarting logical replication after upgrading standby

On Sun, 6 Feb 2022 at 02:20, Axel Rau <Axel(dot)Rau(at)chaos1(dot)de> wrote:

> Am 03.02.22 um 17:06 schrieb Axel Rau:
> > Replication to another standby is working, but the slot of the upgraded
> > standby is inactive.
> Also the subscription has subenabled set to false.
> Enabling it, turns on the active bit at the publisher side, but does not
> start replication.
> Recreating the subscription does not help either.
>
> There should be a solution as logical replication is documented to
> support upgrade of the standby.
>

i just performed an upgrade using pg_upgrade link mode from pg13 to pg14.

the only additional step as mentioned in the docs was to create the
logical replication slot manually.
subscription started working just fine.

postgres(at)controller:/var/tmp/log$ pwd
/var/tmp/log
postgres(at)controller:/var/tmp/log$ /usr/lib/postgresql/14/bin/initdb -D
/var/tmp/log/testdb
postgres(at)controller:/var/tmp/log$ tail postgresql.conf >>
testdb/postgresql.conf
postgres(at)controller:/var/tmp/log$ tail testdb/postgresql.conf
# Add settings for extensions here
wal_level=logical
archive_mode = on
archive_command = '/bin/true'
max_wal_size = 48MB
min_wal_size = 32MB
shared_buffers = 32MB
port = 8001
max_logical_replication_workers = 10

postgres(at)controller:/var/tmp/log$ /usr/lib/postgresql/14/bin/pg_ctl -D
testdb -l logfile start
waiting for server to start.... done
server started
postgres(at)controller:/var/tmp/log$ psql -p 8001
psql (14.1 (Ubuntu 14.1-2.pgdg20.04+1))
Type "help" for help.

postgres=# create table t(id int primary key);
CREATE TABLE
postgres=# create subscription mysub connection 'port=5001' publication
mypub;
NOTICE: created replication slot "mysub" on publisher
CREATE SUBSCRIPTION
postgres=# table t;
id
----
1
2
(2 rows)

*-- after i do an upgrade it stop getting updates from publisher as no slot
on pg14*
*postgres=# select * from pg_stat_subscription;*
* subid | subname | pid | relid | received_lsn | last_msg_send_time |
last_msg_receipt_time | latest_end_lsn | latest_end_time*
*-------+---------+-----+-------+--------------+--------------------+-----------------------+----------------+-----------------*
* 16389 | mysub | | | | |
| |*
*(1 row)*

*-- but when i create the logical replication slot on pg14 (see below), it
starts running just fine*
*postgres=# select * from pg_stat_subscription;*
*postgres=# \x*
*Expanded display is on.*
*postgres=# select * from pg_stat_subscription;*
*-[ RECORD 1 ]---------+---------------------------------*
*subid | 16389*
*subname | mysub*
*pid | 6099*
*relid |*
*received_lsn | 0/C1BC8E0*
*last_msg_send_time | 2022-02-06 03:59:07.272526+05:30*
*last_msg_receipt_time | 2022-02-06 03:59:07.272627+05:30*
*latest_end_lsn | 0/C1BC8E0*
*latest_end_time | 2022-02-06 03:59:07.272526+05:30*

*postgres=# table t;*
*-[ RECORD 1 ]*
*id | 1*
*-[ RECORD 2 ]*
*id | 2*
*-[ RECORD 3 ]*
*id | 3*

-------------------------------------------------------------------------------------------------
upgrade from pg13 to pg14
postgres(at)controller:~/temp/13$ tail postgresql.conf
# Add settings for extensions here
wal_level=logical
archive_mode = on
archive_command = '/bin/true'
max_wal_size = 48MB
min_wal_size = 32MB
shared_buffers = 32MB
port = 5001
max_logical_replication_workers = 10

postgres(at)controller:~/temp/13$ initdb -D pg13
postgres(at)controller:~/temp/13$ cp postgresql.conf pg13/postgresql.conf
postgres(at)controller:~/temp/13$ pg_ctl -D pg13 -l logfile start
waiting for server to start.... done
server started
postgres(at)controller:~/temp/13$ psql -p 5001
psql (13.5 (Ubuntu 13.5-2.pgdg20.04+1))
Type "help" for help.

postgres=# create table t(id int primary key);
CREATE TABLE
postgres=# insert into t values (1);
INSERT 0 1
postgres=# insert into t values (2);
INSERT 0 1
postgres=# checkpoint;
CHECKPOINT
postgres=# create publication mypub for table t;
CREATE PUBLICATION
postgres=# \x
Expanded display is on.
postgres=# select * from pg_replication_slots; -- note the details as we
need to create on pg14 after upgrade
-[ RECORD 1 ]-------+----------
slot_name | mysub
plugin | pgoutput
slot_type | logical
datoid | 13414
database | postgres
temporary | f
active | t
active_pid | 5332
xmin |
catalog_xmin | 489
restart_lsn | 0/15E7098
confirmed_flush_lsn | 0/15E70D0
wal_status | reserved
safe_wal_size |

postgres=# \q
postgres(at)controller:~/temp/13$ pg_ctl -D pg13 -l logfile stop
waiting for server to shut down.... done
server stopped

---------------------------------------
pg14

postgres(at)controller:~/temp/14$ initdb -D /var/lib/postgresql/temp/14/pg14
#perform upgrade
postgres(at)controller:~/temp/14$
/usr/lib/postgresql/${NEW_PSQL}/bin/pg_upgrade -b
/usr/lib/postgresql/${OLD_PSQL}/bin/ -B
/usr/lib/postgresql/${NEW_PSQL}/bin/ -d
/var/lib/postgresql/temp/${OLD_PSQL}/pg${OLD_PSQL} -D
/var/lib/postgresql/temp//${NEW_PSQL}/pg${NEW_PSQL} -o "-c
config-file=/var/lib/postgresql/temp/${OLD_PSQL}/pg${OLD_PSQL}/postgresql.conf"
-O "-c
config-file=/var/lib/postgresql/temp/${NEW_PSQL}/pg${NEW_PSQL}/postgresql.conf"
--link
Performing Consistency Checks
-----------------------------
Checking cluster versions ok
Checking database user is the install user ok
Checking database connection settings ok
Checking for prepared transactions ok
Checking for system-defined composite types in user tables ok
Checking for reg* data types in user tables ok
Checking for contrib/isn with bigint-passing mismatch ok
Checking for user-defined encoding conversions ok
Checking for user-defined postfix operators ok
Creating dump of global objects ok
Creating dump of database schemas
ok
Checking for presence of required libraries ok
Checking database user is the install user ok
Checking for prepared transactions ok
Checking for new cluster tablespace directories ok

If pg_upgrade fails after this point, you must re-initdb the
new cluster before continuing.

Performing Upgrade
------------------
Analyzing all rows in the new cluster ok
Freezing all rows in the new cluster ok
Deleting files from new pg_xact ok
Copying old pg_xact to new server ok
Setting oldest XID for new cluster ok
Setting next transaction ID and epoch for new cluster ok
Deleting files from new pg_multixact/offsets ok
Copying old pg_multixact/offsets to new server ok
Deleting files from new pg_multixact/members ok
Copying old pg_multixact/members to new server ok
Setting next multixact ID and offset for new cluster ok
Resetting WAL archives ok
Setting frozenxid and minmxid counters in new cluster ok
Restoring global objects in the new cluster ok
Restoring database schemas in the new cluster
ok
Adding ".old" suffix to old global/pg_control ok

If you want to start the old cluster, you will need to remove
the ".old" suffix from
/var/lib/postgresql/temp/13/pg13/global/pg_control.old.
Because "link" mode was used, the old cluster cannot be safely
started once the new cluster has been started.

Linking user relation files
ok
Setting next OID for new cluster ok
Sync data directory to disk ok
Creating script to delete old cluster ok
Checking for extension updates ok

Upgrade Complete
----------------
Optimizer statistics are not transferred by pg_upgrade.
Once you start the new server, consider running:
/usr/lib/postgresql/14/bin/vacuumdb --all --analyze-in-stages

Running this script will delete the old cluster's data files:
./delete_old_cluster.sh

#copy the conf file
postgres(at)controller:~/temp/14$ cp postgresql.conf pg14/
postgres(at)controller:~/temp/14$ pg_ctl -D pg14 -l logfile start
waiting for server to start.... done
server started

postgres(at)controller:~/temp/14$ /usr/lib/postgresql/14/bin/vacuumdb -p 5001
--all --analyze-in-stages
vacuumdb: processing database "postgres": Generating minimal optimizer
statistics (1 target)
vacuumdb: processing database "template1": Generating minimal optimizer
statistics (1 target)
vacuumdb: processing database "postgres": Generating medium optimizer
statistics (10 targets)
vacuumdb: processing database "template1": Generating medium optimizer
statistics (10 targets)
vacuumdb: processing database "postgres": Generating default (full)
optimizer statistics
vacuumdb: processing database "template1": Generating default (full)
optimizer statistics
postgres(at)controller:~/temp/14$ psql -p 5001

### this is the only post action after upgrade i had to do (since you would
use ansible, you can automate this my creating slots manually or via if
exists and not via create subscription
psql (14.1 (Ubuntu 14.1-2.pgdg20.04+1))
Type "help" for help.

postgres=# SELECT * FROM pg_create_logical_replication_slot('mysub',
'pgoutput', false, true);
slot_name | lsn
-----------+-----------
mysub | 0/C19E358
(1 row)

postgres=# select * from pg_replication_slots;
postgres=# \x
Expanded display is on.
postgres=# select * from pg_replication_slots;
-[ RECORD 1 ]-------+----------
slot_name | mysub
plugin | pgoutput
slot_type | logical
datoid | 16401
database | postgres
temporary | f
active | t
active_pid | 6100
xmin |
catalog_xmin | 760
restart_lsn | 0/C19E320
confirmed_flush_lsn | 0/C19E358
wal_status | reserved
safe_wal_size |
two_phase | t

--- the below changes get pushed to subscriber just fine. i did not create
publication.
postgres=# insert into t values (3);
INSERT 0 1
postgres=# \q
postgres(at)controller:~/temp/14$ pg_ctl -D pg14 -l logfile stop
waiting for server to shut down.... done
server stopped

--
Thanks,
Vijay
LinkedIn - Vijaykumar Jain <https://www.linkedin.com/in/vijaykumarjain/>