Enable multi-cluster support (optional)

The Kube-Prometheus Helm chart offers support for some multi-cluster use cases. You may need to adjust some recording and alerting rules for your specific architecture. These adjustments go beyond the scope of these instructions.

Add a `cluster` label to rule aggregations

If you want to modify recording and alerting rules to aggregate metrics over a cluster label, you can use cortex-tools’ rules prepare command to add a cluster label to a set of recording and alerting rules. You can modify the aggregation label using the -l flag. The default label is cluster. If you use this command, ensure that you have set the corresponding aggregation label using external_labels in your Prometheus configuration. (If you completed the steps in Migrate a Kube-Prometheus Helm stack, you already set this to cluster: test).

Extract the rules from the Prometheus container by following the instructions in Import recording and alerting rules.
Run the following command in the directory containing the rules files:
```
mimirtool rules prepare -i *.yaml
```
The -i flag modifies the rules files in place. You can omit this flag to test the command. This command modifies many rules to keep or add a cluster label to aggregations, which enables multi-cluster support.

You must then load the rules into Grafana Cloud Alerting by following the instructions in Import recording and alerting rules.