Is there a limit to the number of logical replication subscribers a publisher can have?

Question

I have a number of RDS instances that are set up as subscribers to a single publisher. Today when I tried to add one more, I got the following error:

```
ERROR:  could not connect to the publisher: FATAL:  no pg_hba.conf entry for replication connection from host "172.30.1.134", user "compass", SSL on
```

This is confusing because I've set up subscribers to this DB about ten times before without seeing this issue (and, of course, we don't have access to the pg_hba.conf file in RDS).

I have detailed notes about the process that I always follow:

- The publisher has a user with the `rds_replication` role.
 - I've increased `max_replication_slots` on the publisher.
 - I've even rebooted the publisher

I'm not sure what other steps to take. I'm pretty confused what's happening here.

Accepted Answer

Well, I'm embarrassed to share that this was 100% my fault and I was just working too late. I was trying to connect a replication server to *itself*. That's just not going to work.

When I tried to actually connect it to the publisher, oh, hey, what do you know, it worked!

Is there a limit to the number of logical replication subscribers a publisher can have?

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