[stable/prometheus] harmonization of regex references without braces

[pdemagny]

Signed-off-by: Pierre DEMAGNY pierre.demagny@citymeo.fr

What this PR does / why we need it:

This PR harmonizes regex references in values.yaml. There were some references with braces, some without. Removed all occurences of reference with braces to avoid breaking external tools like Terraform Template Provider, for example:

data "template_file" "prometheus_tmpl" {
  template = "${file("templates/values-prometheus.yaml.tmpl")}"

  vars {
    PROMETHEUS_INGRESS_HOST   = "${local.workspace["prometheus_ingress_host"]}"
    PROMETHEUS_INGRESS_PATH   = "${local.workspace["prometheus_ingress_path"]}"
  }
}

server:
...
  ingress:
...
    ## Prometheus server Ingress hostnames with optional path
    ## Must be provided if Ingress is enabled
    ##
    hosts:
      - ${PROMETHEUS_INGRESS_HOST}${PROMETHEUS_INGRESS_PATH}
    #   - domain.com/prometheus

Regex references of the form ${n} are interpolated by Terraform's Template Provider, so for example in:

      - job_name: 'kubernetes-nodes'
...
        kubernetes_sd_configs:
          - role: node

        relabel_configs:
          - action: labelmap
            regex: __meta_kubernetes_node_label_(.+)
          - target_label: __address__
            replacement: kubernetes.default.svc:443
          - source_labels: [__meta_kubernetes_node_name]
            regex: (.+)
            target_label: __metrics_path__
            replacement: /api/v1/nodes/${1}/proxy/metrics

My __metrics_path__ end up with /api/v1/nodes/1/proxy/metrics and the 'kubernetes-nodes' job does not work.

When using regex references of the form $n, they are not interpolated and labelling magic works:

      - job_name: 'kubernetes-nodes'
...
        kubernetes_sd_configs:
          - role: node

        relabel_configs:
          - action: labelmap
            regex: __meta_kubernetes_node_label_(.+)
          - target_label: __address__
            replacement: kubernetes.default.svc:443
          - source_labels: [__meta_kubernetes_node_name]
            regex: (.+)
            target_label: __metrics_path__
            replacement: /api/v1/nodes/$1/proxy/metrics

My __metrics_path__ end up with /api/v1/nodes/<node_name>/proxy/metrics where <node_name> is the name of each of my nodes and the 'kubernetes-nodes' job works.

Which issue this PR fixes

There were no open issues for this.

Checklist

• DCO signed
• Chart Version bumped

[gianrubio]

/ok-to-test
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gianrubio, pdemagny

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