Re: restarting logical replication after upgrading standby

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Oh sorry, I missed the part of you upgrading the subscriber as well. I'll need to check that too, will get back on this tomorrow (too late now)


On Sun, Feb 6, 2022, 4:11 AM Vijaykumar Jain <vijaykumarjain.github@xxxxxxxxx> wrote:

On Sun, 6 Feb 2022 at 02:20, Axel Rau <Axel.Rau@xxxxxxxxx> 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@controller:/var/tmp/log$ pwd
/var/tmp/log
postgres@controller:/var/tmp/log$ /usr/lib/postgresql/14/bin/initdb -D /var/tmp/log/testdb
postgres@controller:/var/tmp/log$ tail postgresql.conf >> testdb/postgresql.conf
postgres@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@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@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@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@controller:~/temp/13$ initdb -D pg13
postgres@controller:~/temp/13$ cp postgresql.conf pg13/postgresql.conf
postgres@controller:~/temp/13$ pg_ctl -D pg13 -l logfile start
waiting for server to start.... done
server started
postgres@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@controller:~/temp/13$  pg_ctl -D pg13 -l logfile stop
waiting for server to shut down.... done
server stopped


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

postgres@controller:~/temp/14$ initdb -D /var/lib/postgresql/temp/14/pg14
#perform upgrade
postgres@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@controller:~/temp/14$ cp postgresql.conf pg14/
postgres@controller:~/temp/14$ pg_ctl -D pg14 -l logfile start
waiting for server to start.... done
server started

postgres@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@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@controller:~/temp/14$ pg_ctl -D pg14  -l logfile stop
waiting for server to shut down.... done
server stopped


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