Maximum number subscribers node in PostgreSQL logical replication?

Question

Does anyone know what is the maximum of subscriber nodes with PostgreSQL 11 logical replication ?

Answer 1

The limit built into PostgreSQL is 262143 (2¹⁸ - 1).

So in theory you could bump up required parameters and have 200k logical rep subscribers.

In reality, you will start hitting performance issues much below this.

For the parameters - see documentation and also see this SQL query:

SELECT category, name, setting, min_val, boot_val, max_val
FROM pg_settings
WHERE category ~* 'replica'
AND name ~* 'max.*(workers|slots|senders)'

I get this:

 category | name | setting | min_val | boot_val | max_val 
-------------------------------+-----------------------------------+---------+---------+----------+---------
 Replication / Subscribers | max_logical_replication_workers | 4 | 0 | 4 | 262143
 Replication / Sending Servers | max_replication_slots | 10 | 0 | 10 | 262143
 Replication / Subscribers | max_sync_workers_per_subscription | 2 | 0 | 2 | 262143
 Replication / Sending Servers | max_wal_senders | 10 | 0 | 10 | 262143
(4 rows)