ruler doesn't support global external labels

[jml]

You can configure Prometheus to add labels to any time series or alert that it sends to other systems using global.external_labels (see https://prometheus.io/docs/operating/configuration/#configuration-file).

It uses these labels when writing output for recording and alerting rules.

Because our rules configuration only allows for rules files, we have no way of supporting this setting in the ruler.

[jtlisi]

#1571 will make these a bit easier to implement. The upstream Prometheus rules Manager has the params for external labels in this function: https://github.com/prometheus/prometheus/blob/37d666949c9475e298666cc8e0e787d76fa8fd77/rules/manager.go#L825

However, we will need to allow users to configure their rules with external labels

[stale]

This issue has been automatically marked as stale because it has not had any activity in the past 30 days. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[gotjosh]

We should also consider specifying whenever the global external labels should be applied to alerts or rules or both.

[jtlisi]

@gotjosh I think it would make sense for the external label to be directly associated with the rule group.

[gouthamve]

We also need alert_relabel_rules as part of the global config.

[gotjosh]

The stanza described by Goutham is: https://prometheus.io/docs/prometheus/latest/configuration/configuration/#alert_relabel_configs