Prometheus: Allow input of TLS client creds in values.yaml

Some scrape targets require the use of TLS client certificates, which
are specified as filenames as part of the tls_config.

This change allows these client certs and keys to be provided, stores
them in a secret, and mounts them in the pod under /tls_configs.

Example:

    tls_configs:
      kubernetes-etcd:
        ca.pem: |
          -----BEGIN CERTIFICATE-----
          -----END CERTIFICATE-----
        crt.pem: |
          -----BEGIN CERTIFICATE-----
          -----END CERTIFICATE-----
        key.pem: |
          -----BEGIN RSA PRIVATE KEY-----
          -----END RSA PRIVATE KEY-----

    conf:
      prometheus:
        scrape_configs:
          template: |
            scrape_configs:
              - job_name: kubernetes-etcd
                scheme: https
                tls_config:
                  ca_file: /tls_configs/kubernetes-etcd.ca.pem
                  cert_file: /tls_configs/kubernetes-etcd.cert.pem
                  key_file: /tls_configs/kubernetes-etcd.key.pem

Change-Id: I963c65dc39f1b5110b091296b93e2de9cdd980a4

prometheus/templates/secret-tls-configs.yaml

@@ -0,0 +1,27 @@
+{{/*
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/}}
+
+{{- if .Values.tls_configs }}
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: {{ .Release.Name }}-tls-configs
+data:
+{{- range $k, $v := .Values.tls_configs }}
+{{- range $f, $c := $v }}
+  {{ $k }}.{{ $f }}: {{ $c | b64enc }}
+{{- end }}
+{{- end }}
+{{- end }}

prometheus/templates/statefulset.yaml

@@ -204,6 +204,10 @@ spec:
               readOnly: true
             - name: storage
               mountPath: /var/lib/prometheus/data
+{{- if .Values.tls_configs }}
+            - name: tls-configs
+              mountPath: /tls_configs
+{{- end }}
 {{ if $mounts_prometheus.volumeMounts }}{{ toYaml $mounts_prometheus.volumeMounts | indent 12 }}{{ end }}
       volumes:
         - name: pod-tmp
@@ -220,6 +224,12 @@ spec:
           configMap:
             name: {{ printf "%s-%s" $envAll.Release.Name "prometheus-bin" | quote }}
             defaultMode: 0555
+{{- if .Values.tls_configs }}
+        - name: tls-configs
+          secret:
+            secretName: {{ printf "%s-%s" $envAll.Release.Name "tls-configs" | quote }}
+            defaultMode: 0444
+{{- end }}
 {{ if $mounts_prometheus.volumes }}{{ toYaml $mounts_prometheus.volumes | indent 8 }}{{ end }}
 {{- if not .Values.storage.enabled }}
         - name: storage

prometheus/values.yaml

@@ -250,6 +250,26 @@ secrets:
       prometheus:
         public: prometheus-tls-public
 
+tls_configs:
+  # If client certificates are required to connect to metrics endpoints, they
+  # can be configured here. They will be mounted in the pod under /tls_configs
+  # and can be referenced in scrape configs.
+  # The filenames will be the key and subkey concatenanted with a ".", e.g.:
+  #   /tls_configs/kubernetes-etcd.ca.pem
+  #   /tls_configs/kubernetes-etcd.crt.pem
+  #   /tls_configs/kubernetes-etcd.key.pem
+  # From the following:
+  # kubernetes-etcd:
+  #   ca.pem: |
+  #     -----BEGIN CERTIFICATE-----
+  #     -----END CERTIFICATE-----
+  #   crt.pem: |
+  #     -----BEGIN CERTIFICATE-----
+  #     -----END CERTIFICATE-----
+  #   key.pem: |
+  #     -----BEGIN RSA PRIVATE KEY-----
+  #     -----END RSA PRIVATE KEY-----
+
 storage:
   enabled: true
   pvc: