On 12/31/16 10:00 AM, Magnus Hagander wrote: > max_wal_senders=10 > max_replication_slots=20
How about we default max_replication_slots to -1, which means to use the same value as max_wal_senders?
I think this would address the needs of 99% of users. If we do like you suggest, there are going to be very many users who forget to adjust these two values together, and very many who will do it but will be puzzled and annoyed by it. Since we're now pushing the use of replication slots even more (your pg_basebackup change, upcoming logical replication), I think this could be a major source of misconfigurations.
But you don't necessarily want to adjust them together, do you? They are both capped by max_connections, but I don't think they have any other direct relation between each other?