Improve jsonnet parser for rules

[v-zhuravlev]

Hi! Even though it says deprecated for using hidden fields, we still using it extensively for monitoring-mixins development, especially in grr watch mode.

It works great for 'dashboards only' mixins that way, but unfortunately, it stops working when rules are present, error is recevied:

2022-04-17 02:34:04.863636 I | 02:34:04 Error:  RUNTIME ERROR: Unexpected type string, expected number
        mixin.libsonnet:69:28-65
        mixin.libsonnet:75:17-31        thunk from <thunk from <function <fromMap>>>
        mixin.libsonnet:8:58-62 thunk from <thunk from <thunk from <object <anonymous>>>>
        mixin.libsonnet:8:43-76 thunk from <thunk from <object <anonymous>>>
        mixin.libsonnet:8:28-90 thunk from <object <anonymous>>
        mixin.libsonnet:8:13-103        object <anonymous>
        During manifestation

This is due grizzly.jsonnet expects rules to be wrapped in the namespace:

  prometheusAlerts+:: {
    grizzly_rules: { <--namespace
      groups: [{
        name: 'my_rules_group',
        rules: [
          $.alert,
        ],
      }],
    },
  },

while monitoring-mixins by convention have alerts defined without one:

  _config+:: {
  ...
  },
  grafanaDashboards+:: {
  ...
  },
  prometheusRules+:: {
  ...
  },
  prometheusAlerts+:: {
      groups: [{
        name: 'my_rules_group',
        rules: [
          $.alert,
        ],
      }],
  },

(some examples:
https://github.com/prometheus/node_exporter/blob/master/docs/node-mixin/alerts/alerts.libsonnet
https://github.com/prometheus/prometheus/blob/main/documentation/prometheus-mixin/alerts.libsonnet
)

So here is the suggested improvement for jsonnet rule parser that:

• Parses rule groups even if they are not wrapped into namespace. This is extremely useful when working with monitoring-mixins. 'grizzly_rules' namespace is added
• Loads all rule groups instead of the first one.

This fix not only allows loading of monitoring-mixins dashboards inside grafana without any grizzly specific changes to original mixin, but also can load monitoring-mixins alerts into cortex as well:

user@vzhuravl-mac node-mixin % ../../../grizzly/cmd/grr/grr  watch .  mixin.libsonnet 
INFO[0000] Watching for changes                         
INFO[0001] Changes detected. Applyingmixin.libsonnet    
INFO[0001] Applying 8 resources                         
Dashboard.node-rsrc-use updated
Dashboard.nodes-darwin updated
Dashboard.nodes updated
Dashboard.node-multicluster-rsrc-use updated
PrometheusRuleGroup.grizzly_rules.node-exporter.rules no differences
PrometheusRuleGroup.abc.node-exporter-small no differences
PrometheusRuleGroup.zzz.node-exporter-small2 no differences
PrometheusRuleGroup.zzz.node-exporter no differences

[malcolmholmes]

Minor comments, looks otherwise done well, thanks!

[malcolmholmes]

if key in main is true, then doesn't this result in an array within an array?

[v-zhuravlev]

Good point! Still, grizzly tolerated that :) Updated to use nested loop without extra array in the result.

[malcolmholmes]

Looks great, thanks for this.