Re: There is no description about "Logical Replication also use or occupy max_wal_senders ",

On Wed, Aug 23, 2023, at 10:55 AM, PG Doc comments form wrote:
> max_wal_senders (integer)
>
> Specifies the maximum number of concurrent connections from standby servers
> or streaming base backup clients (i.e., the maximum number of simultaneously
> running WAL sender processes). The default is 10. The value 0 means
> replication is disabled. Abrupt disconnection of a streaming client might
> leave an orphaned connection slot behind until a timeout is reached, so this
> parameter should be set slightly higher than the maximum number of expected
> clients so disconnected clients can immediately reconnect. This parameter
> can only be set at server start. Also, wal_level must be set to replica or
> higher to allow connections from standby servers.
>
> When running a standby server, you must set this parameter to the same or
> higher value than on the primary server. Otherwise, queries will not be
> allowed in the standby server.
>
>
>
> In the above description， there is no description about "Logical Replication
> also use or occupy max_wal_senders ",

According to the glossary [1], standby server (referred as "replica") is

Replica (server)
A database that is paired with a primary database and is maintaining a copy of
some or all of the primary database's data. The foremost reasons for doing this
are to allow for greater access to that data, and to maintain availability of
the data in the event that the primary becomes unavailable.

... and it implies both (logical and physical) replicas. The logical
replication [2] setup also informs that you need to adjust max_wal_senders.

Maybe the "standby" terminology could be expanded to avoid confusion for users
from other technologies. If I were to suggest a modification, it would be in
the first paragraph in the "Replication" section [3] (something like "Primaries
can send data, while standbys are always receivers of physically or logically
replicated data") or even better rephrase the "Replica (server)" term in the
glossary [1].

> so, I suggest the following modification:
> Specifies the maximum number of concurrent connections from standby servers
> or streaming base backup clients and Logical Replication (i.e., the
> maximum number of simultaneously running WAL sender processes). ---please
> note ,"and Logical Replication" is newly added。
>

The logical replication feature wasn't newly added. It was added almost 6 years
ago and version 10 (that adds it) was EOL more than 9 months ago.

[1] https://www.postgresql.org/docs/current/glossary.html
[2] https://www.postgresql.org/docs/current/logical-replication-config.html
[3] https://www.postgresql.org/docs/current/runtime-config-replication.html

--
Euler Taveira
EDB https://www.enterprisedb.com/