Metrics from multiple RDS instances on different versions not shown

[urbann3]

What did you do?
Configured exporter to pull metrics from multiple instances via DATA_SOURCE_NAME environment variable with a comma separated list. All targets are RDS, some of them are on Postgres version 11.x, some on 12.x and 13.x, however looks like the exporter is not happy when I try mixing the versions as no metrics are shown. If I configure the exporter to pull only from database running on version 11.x, it is okay, metrics are shown, same goes for 12.x and 13.x, but not all together.
I am not sure if this is expected or not?

What did you expect to see?
Metrics, lots of them, from multiple RDS versions :)

What did you see instead? Under which circumstances?

Environment
Exporter running in Kubernetes cluster on EKS

• postgres_exporter version:
  v0.10.1
  v0.11.0
  v0.12.0-rc.0

• PostgreSQL version:
  11.x
  12.x
  13.x

• Logs:
  No errors in the logs, it is making successful connection to each database regardless of database version

[sysadmind]

This is unexpected. I did some local testing and I can confirm this problem. I have traced the root cause to the fact that the pg_settings dynamically sets the help text on metrics to the description from the database:

postgres_exporter/cmd/postgres_exporter/pg_setting.go

Line 73 in ac9fa13

shortDesc = s.shortDesc

To fix this, we should probably stop dynamically setting the help text from the database. Thanks for the feedback.

[oleksii-karpenko-rri]

We have almost the same issue: three instances are in DATA_SOURCE_NAME, all with version 11.
In logs:
ts=2022-12-19T15:59:22.837Z caller=collector.go:196 level=error msg="collector failed" name=database duration_seconds=0.01336918 err="pq: permission denied for database rdsadmin"