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From: Chris Hoover <chrish@aweber.com>
To: pgsql-admin@lists.postgresql.org
Subject: Help with logical replication: pg_replication_slots.active_pid is null????
Date: Sun, 16 Jul 2023 20:30:59 -0400
Message-ID: <3DF8573D-9E47-4770-94A1-C0B873BD1D7C@aweber.com> (raw)

Hey Everyone,

Need some help with logical replication.  I’m trying to move my mail 2.5TB database to a new postgres server and upgrade from 14-15 at the same time.  I’m running into some strange issues.

1. my pg_replication_slots are filling up with entries that have no active pid.  I can’t figure out what is going on here.
```
15> select * from pg_replication_slots

 pg_67341299_sync_92244_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698512637 │ 1270/84298C10 │ 1270/843169A8       │ reserved   │        (null) │ f
 pg_67341299_sync_89883_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698171095 │ 126E/20D13A50 │ 126E/20D13A88       │ extended   │        (null) │ f
 pg_67341299_sync_90126_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698167442 │ 126E/1F66FFC8 │ 126E/1F670000       │ extended   │        (null) │ f
 pg_67341299_sync_92637_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698153629 │ 126E/1A732E08 │ 126E/1A732EE0       │ extended   │        (null) │ f
 pg_67341299_sync_89526_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698041660 │ 126D/E5A0E4C0 │ 126D/E5A10CC8       │ extended   │        (null) │ f
 pg_67341299_sync_89604_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698177047 │ 126E/231CBD58 │ 126E/231CBE30       │ extended   │        (null) │ f
 pg_67341299_sync_92447_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698233353 │ 126E/53D730B0 │ 126E/53D730E8       │ extended   │        (null) │ f
 pg_67341299_sync_93707_7249511065961178394 │ pgoutput │ logical   │  16387 │ xxx      │ f         │ f      │     (null) │ (null) │    698171095 │ 126E/20D1C608 │ 126E/20D1ECB0       │ extended   │        (null) │ f
```

2. I’m getting way more tables marked as copying than should be allowed.  Says I have 619 tables copying.  However, I’m limited to 10 replication slots on the master and have max_sync_workers_per_subscription set to 8.  That should mean at any given time I have 8 tables copying during the initial data load.  (Other 2 slots are for the main logical replication slot and our patroni replication).  I don’t understand what is happening.  I would love to bump my replication slots on the current primary, but that requires an outage.
```
15> BEGIN;
select current_timestamp,
       case srsubstate
         when 'i' then 'Initialized'
         when 'd' then 'Data Copying'
         when 'f' then 'Finished'
         when 's' then 'Synchronized'
         when 'r' then 'Ready'
       end as table_state,
       count(*)
  from pg_subscription_rel group by srsubstate order by srsubstate;
select pg_size_pretty(pg_database_size(current_database()));
rollback;
BEGIN
       current_timestamp       | table_state  | count
-------------------------------+--------------+-------
 2023-07-16 20:23:13.780121-04 | Data Copying |   619
 2023-07-16 20:23:13.780121-04 | Initialized  |   721
 2023-07-16 20:23:13.780121-04 | Ready        |   152
 2023-07-16 20:23:13.780121-04 | Synchronized |    19
(4 rows)
```

Any advice would be welcome.  I need to get this database replicated and ready to failover as soon as possible.  Initially we are scheduled for this Thursday (7/20) for the failover, but of course replication has to be current before then.

Thanks,


Chris Hoover
Senior DBA
AWeber.com
Cell: (803) 528-2269
Email: chrish@aweber.com

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