added prometheus rules to the helm chart

[miminar]

• ContainerEphemeralStorageUsageAtLimit
• ContainerEphemeralStorageUsageReachingLimit
• EphemeralStorageVolumeFilledUp
• EphemeralStorageVolumeFillingUp

That's what we have/use at the moment. If you wish, I could make the individual alerts toggle-able.

There is a potential for additional NodeOutOfEphemeralStorage and NodeRunningOutOfEphemeralStorage or similar, but since we don't have them yet, I'd leave them for a possible follow-up.

Please take a look.

[miminar]

Also, to further avoid spam, the following inhibit rules could be recommended (viz kubectl explain alertmanagerconfigs.monitoring.coreos.com.spec.inhibitRules):

        - source_matchers:
            - alertname="EphemeralStorageVolumeFilledUp"
          target_matchers:
            - severity="warning"
            - alertname="EphemeralStorageVolumeFillingUp"
          equal:
            - pod_namespace
            - pod_name
            - volume_name
        - source_matchers:
            - alertname="ContainerEphemeralStorageUsageAtLimit"
          target_matchers:
            - severity="warning"
            - alertname="ContainerEphemeralStorageUsageReachingLimit"
          equal:
            - pod_namespace
            - pod_name
            - exported_container

I'll try to squeeze it into the README

[jmcgrath207]

Just released 1.11.1 with your change

[miminar]

Awesome, thank you for swift review and new release!