jsonnet/microservices: create separate configmap for overrides

[yvrhdn]

Is your feature request related to a problem? Please describe.
The current microservices Jsonnet library creates a single configmap per component which contains both the Tempo config and the overrides. This spreads out the overrides configuration, which is updated more often.

We'd like to combine all the overrides in a single configmap which is mounted by the components that need it (distributors, ingesters and compactors). This way only this configmap needs to be managed.

Describe the solution you'd like
Create a new configmap (e.g. tempo-overrides?) that contains all the overrides information.

Describe alternatives you've considered
We can also not do this ofc.

Additional context

For example: this if how the distributor configmap is created right now:

tempo/operations/jsonnet/microservices/configmap.libsonnet

Lines 102 to 111 in f822caa

	tempo_distributor_configmap:
	configMap.new('tempo-distributor') +
	configMap.withData({
	'tempo.yaml': k.util.manifestYaml($.tempo_distributor_config),
	}) +
	configMap.withDataMixin({
	'overrides.yaml': k.util.manifestYaml({
	overrides: $._config.overrides,
	}),
	}),

And this is how it is mounted:

tempo/operations/jsonnet/microservices/distributor.libsonnet

Lines 47 to 49 in f822caa

	deployment.mixin.spec.template.spec.withVolumes([
	volume.fromConfigMap(tempo_config_volume, $.tempo_distributor_configmap.metadata.name),
	]),

If we change how the overrides.yaml is mounted, we'll have to update the Tempo config as well:

tempo/operations/jsonnet/microservices/configmap.libsonnet

Lines 44 to 46 in f822caa

	overrides: {
	per_tenant_override_config: '/conf/overrides.yaml',
	},

[yvrhdn]

This can be a fun issue if you want to learn more about kubernetes and jsonnet 🙂

To try out this jsonnet library locally, you can use the microservices example in example/tk: https://github.com/grafana/tempo/tree/main/example/tk