Add extraContainers to fluentd chart

Copy the templating and the examples in
the values file from the fluent-bit chart.

Author: tghartland

charts/fluentd/templates/_pod.tpl

@@ -87,6 +87,13 @@ containers:
     - mountPath: /var/log/fluent
       name: {{ include "fluentd.fullname" . }}-buffer
     {{- end }}
+{{- if .Values.extraContainers }}
+  {{- if kindIs "string" .Values.extraContainers }}
+    {{- tpl .Values.extraContainers $ | nindent 2 }}
+  {{- else }}
+    {{-  toYaml .Values.extraContainers | nindent 2 }}
+  {{- end -}}
+{{- end }}
 volumes:
 - name: etcfluentd-main
   configMap:

charts/fluentd/values.yaml

@@ -174,6 +174,21 @@ envFrom: []
 
 initContainers: []
 
+# This supports either a structured array or a templatable string
+extraContainers: []
+
+# Array mode
+# extraContainers:
+#   - name: do-something
+#     image: busybox
+#     command: ['do', 'something']
+
+# String mode
+# extraContainers: |-
+#   - name: do-something
+#     image: bitnami/kubectl:{{ .Capabilities.KubeVersion.Major }}.{{ .Capabilities.KubeVersion.Minor }}
+#     command: ['kubectl', 'version']
+
 ## Name of the configMap containing a custom fluentd.conf configuration file to use instead of the default.
 # mainConfigMapNameOverride: ""