Feature: Cluster Chart PrometheusRule alerts

[itay-grudev]

Automated alerts for cluster issues would be extremely useful to improve the safety of a CNPG cluster.

Ideally, alerts should come in both a warning and critical severity levels, so that users have time to react to an alert before a problem escalates.

Proposed alerts should include:

• Instance failure based on the cluster spec
• Low Disk space
• High Replication Lag
• High connection count on any instance

There are some alerts such as high CPU usage and/or memory that are already covered by kube-prometheus-stack and should not be implemented here.

[maxpain]

@itay-grudev could you also add PrometheusRule to the cloudnative-pg chart?

[itay-grudev]

@maxpain That makes sense. Can you create a new issue for this feature request? Please mention wWhat kind of alerts are you missing in addition to alerting if the operator deployment has no replicas.