matrix-prometheus-postgres-exporter pg_ls_waldir permission denied error

[joecool1029]

Describe the bug

Dec 13 18:41:02 xwaretech.net matrix-postgres[32910]: 2023-12-13 18:41:02.352 UTC [111] STATEMENT:
Dec 13 18:41:02 xwaretech.net matrix-postgres[32910]: SELECT
Dec 13 18:41:02 xwaretech.net matrix-postgres[32910]: COUNT(*) AS segments,
Dec 13 18:41:02 xwaretech.net matrix-postgres[32910]: SUM(size) AS size
Dec 13 18:41:02 xwaretech.net matrix-postgres[32910]: FROM pg_ls_waldir()
Dec 13 18:41:02 xwaretech.net matrix-postgres[32910]: WHERE name ~ '^[0-9A-F]{24}$'
Dec 13 18:41:02 xwaretech.net matrix-prometheus-postgres-exporter[35638]: ts=2023-12-13T18:41:02.352Z caller=collector.go:199 level=error
msg="collector failed" name=wal duration_seconds=0.028922192 err="pq: permission denied for function pg_ls_waldir"

To Reproduce
My vars.yml file looks like this:

prometheus_enabled: true
prometheus_node_exporter_enabled: true
prometheus_postgres_exporter_enabled: true
grafana_enabled: true
matrix_synapse_metrics_enabled: true

Expected behavior
Expect to not see these errors.

Matrix Server:

• OS: Ubuntu 22.04
• amd64

Additional context
Looks to be this issue: bitnami/charts#20247 just not sure on best way to resolve issue.

[masikrus]

GRANT pg_monitor TO readonly_user;

[joecool1029]

Ok so I did:

GRANT pg_monitor TO matrix_prometheus_postgres_exporter;

Error stopped happening (this had been going for weeks)

REVOKE pg_monitor FROM matrix_prometheus_postgres_exporter;

brings it back. Not sure if this is giving it too many permissions, but it will get it working granting it this role.