Re: WAL accumulating, Logical Replication pg 13

Yeah, indexes could slow things down, thanks. Btw I'm not using logical
replication for the upgrade, that's not supported for 9.3.
It was more complicated but that's beside the point.

I could just delete the publication and all that belongs to it and start
over. But since I'm trying out logical replication, I would like to be more
in control than that. It's there anything that I can dig into to find out
why the WAL is accumulating?

Op vr 28 mei 2021 22:20 schreef Vijaykumar Jain <
vijaykumarjain(dot)github(at)gmail(dot)com>:

> I am not too sure with 9.3
> i tried an upgrade from 9.6 to 11 using logical replication (pg_logical
> extension)
>
> one thing to note.
> logical replication initiates a copy from a snapshot, then changes from
> then on.
>
> I had a very high insert rate on my source tables (v9.6) and the
> destination (v11) could not keep up (it had tons of indexes when I copied
> the schema) and it took around a day as the table had around 12 indexes.
>
> So at the destination(v11), I dropped all but the primary index for each
> table, started subscription and when it was almost caught up, rebuilt the
> index on the destination concurrently.
> it completed in 4-5 hours without stopping the source.
> migration completed in a few mins :)
>
> not sure if this would help, but just FYI.
>
>
> On Sat, 29 May 2021 at 01:36, Willy-Bas Loos <willybas(at)gmail(dot)com> wrote:
>
>> Hi , I'm upgrading a 1.5TB database from postgres 9.3 to postgres 13 on
>> Debian 10. This is now in an Acceptance stage (DTAP). I have encountered a
>> problem: the WAL is not being deleted. I now have 1.4 TB of WAL in pg_wal
>> and my disks are getting full. The oldest WAL file is 18 days old.
>> I use Logical Replication from the new cluster to another new cluster
>> with 1 subscriber and 1 subscription.
>>
>> pg_stat_subscription tells me all recent timestamps.
>> and this:
>> db=# select * from pg_replication_slots;
>> -[ RECORD 1 ]-------+-------------
>> slot_name | my_pub1
>> plugin | pgoutput
>> slot_type | logical
>> datoid | 16401
>> database | db
>> temporary | f
>> active | t
>> active_pid | 9480
>> xmin |
>> catalog_xmin | 269168
>> restart_lsn | D4/908BC268
>> confirmed_flush_lsn | E1/25BF5710
>> wal_status | extended
>> safe_wal_size |
>>
>>
>>
>> I've had problems with diskspace on this server, with postgres crashing
>> because of it, then added more diskspace and postgres recovered. This
>> doesn't seem to be a problem now.
>>
>> The *publication* has the options publish = 'insert, update, delete,
>> truncate', publish_via_partition_root = false
>> The *subscription* has the options connect = true, enabled = true,
>> create_slot = false, slot_name = my_pub1, synchronous_commit = 'off'
>>
>> The log on the publisher says:
>> 2021-05-25 21:25:18.973 CEST [4584] user(at)db LOG: starting logical
>> decoding for slot "my_pub1"
>> 2021-05-25 21:25:18.973 CEST [4584] user(at)db DETAIL: Streaming
>> transactions committing after D6/A82B5FE0, reading WAL from D4/908BC268.
>> 2021-05-25 21:25:18.973 CEST [4584] user(at)db LOG: logical decoding found
>> consistent point at D4/908BC268
>> 2021-05-25 21:25:18.973 CEST [4584] user(at)db DETAIL: There are no
>> running transactions.
>> 2021-05-25 21:29:49.456 CEST [4614] user(at)db ERROR: replication slot
>> "my_pub1" is active for PID 4584
>> 2021-05-25 21:29:54.474 CEST [4615] user(at)db ERROR: replication slot
>> "my_pub1" is active for PID 4584
>>
>> And on the subscriber:
>> 2021-05-28 21:23:46.702 CEST [40039] LOG: logical replication apply
>> worker for subscription "my_pub1" has started
>> 2021-05-28 21:23:46.712 CEST [40039] ERROR: could not start WAL
>> streaming: ERROR: replication slot "my_pub1" is active for PID 730
>> 2021-05-28 21:23:46.714 CEST [19794] LOG: background worker "logical
>> replication worker" (PID 40039) exited with exit code 1
>>
>> The postgres settings on the *publisher* are:
>> max_connections = 100 # (change requires restart)
>> tcp_keepalives_idle = 120 # TCP_KEEPIDLE, in seconds;
>> shared_buffers = 50GB # min 128kB
>> work_mem = 1GB # min 64kB
>> maintenance_work_mem = 10GB # min 1MB
>> logical_decoding_work_mem = 5GB # min 64kB
>> dynamic_shared_memory_type = posix # the default is the first option
>> max_worker_processes = 20 # (change requires restart)
>> max_parallel_maintenance_workers = 10 # taken from max_parallel_workers
>> max_parallel_workers_per_gather = 5 # taken from max_parallel_workers
>> max_parallel_workers = 15 # maximum number of max_worker_processes that
>> wal_level = logical # minimal, replica, or logical
>> max_wal_size = 1GB
>> min_wal_size = 80MB
>> #archive_mode = off
>> max_wal_senders = 10 # max number of walsender processes
>> wal_sender_timeout = 1min # in milliseconds; 0 disables
>> max_replication_slots = 7 # max number of replication slots
>>
>> On postgres settings on the *subscriber*:
>> max_connections = 100 # (change requires restart)
>> tcp_keepalives_idle = 120 # TCP_KEEPIDLE, in seconds;
>> shared_buffers = 25GB # min 128kB
>> work_mem = 1GB # min 64kB
>> maintenance_work_mem = 10GB # min 1MB
>> logical_decoding_work_mem = 5GB # min 64kB
>> dynamic_shared_memory_type = posix # the default is the first option
>> max_worker_processes = 20 # (change requires restart)
>> max_parallel_maintenance_workers = 10 # taken from max_parallel_workers
>> max_parallel_workers_per_gather = 5 # taken from max_parallel_workers
>> max_parallel_workers = 15 # maximum number of max_worker_processes that
>> wal_level = logical # minimal, replica, or logical
>> max_wal_size = 3GB
>> min_wal_size = 80MB
>> #archive_mode = off
>> wal_receiver_timeout = 1min # time that receiver waits for
>> max_logical_replication_workers = 10 # taken from max_worker_processes
>> max_sync_workers_per_subscription = 5 # taken from
>> max_logical_replication_workers
>>
>> I've tried increasing wal_sender_timeout and wal_receiver_timeout to 10
>> minutes each, but this had no positive effect.
>>
>> Some advice would be helpful
>> --
>> Willy-Bas Loos
>>
>
>
> --
> Thanks,
> Vijay
> Mumbai, India
>