support additional environment variables in hub deployment

jupyterhub/schema.yaml

@@ -866,6 +866,38 @@ properties:
         description: |
           Deprecated and no longer does anything. Use the user-scheduler instead
           in order to accomplish a good packing of the user pods.
+      extraEnv:
+        type: object
+        description: |
+          Extra environment variables that should be set for the user pods.
+          String literals with `$(ENV_VAR_NAME)` will be expanded by Kubelet which
+          is a part of Kubernetes. Note that the user pods will already have
+          access to a set of environment variables that you can use, like
+          `JUPYTERHUB_USER` and `JUPYTERHUB_HOST`. For more information about these
+          inspect [this source
+          code](https://github.com/jupyterhub/jupyterhub/blob/cc8e7806530466dce8968567d1bbd2b39a7afa26/jupyterhub/spawner.py#L763).
+          ```yaml
+          singleuser:
+            extraEnv:
+              # basic notation (for literal values only)
+              MY_ENV_VARS_NAME1: "my env var value 1"
+              # explicit notation (the "name" field takes precedence)
+              USER_NAMESPACE:
+                name: USER_NAMESPACE
+                valueFrom:
+                  fieldRef:
+                    fieldPath: metadata.namespace
+              # implicit notation (the "name" field is implied)
+              PREFIXED_USER_NAMESPACE:
+                value: "my-prefix-$(USER_NAMESPACE)"
+              SECRET_VALUE:
+                valueFrom:
+                  secretKeyRef:
+                    name: my-k8s-secret
+                    key: password
+          ```
+          For more information, see the [Kubernetes EnvVar
+          specification](https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.18/#envvar-v1-core).
       extraTolerations:
         type: list
         description: |

jupyterhub/templates/_helpers.tpl

@@ -267,3 +267,42 @@ limits:
   {{- end }}
 {{- end }}
 {{- end }}
+
+{{- /*
+  jupyterhub.extraEnv:
+    Output YAML formatted EnvVar entries for use in a containers env field.
+*/}}
+{{- define "jupyterhub.extraEnv" -}}
+{{- include "jupyterhub.extraEnv.withTrailingNewLine" . | trimSuffix "\n" }}
+{{- end }}
+
+{{- define "jupyterhub.extraEnv.withTrailingNewLine" -}}
+{{- if . }}
+{{- /* If extraEnv is a list, we inject it as it is. */}}
+{{- if eq (typeOf .) "[]interface {}" }}
+{{- . | toYaml }}
+
+{{- /* If extraEnv is a map, we differentiate two cases: */}}
+{{- else if eq (typeOf .) "map[string]interface {}" }}
+{{- range $key, $value := . }}
+{{- /*
+    - If extraEnv.someKey has a map value, then we add the value as a YAML
+      parsed list element and use the key as the name value unless its
+      explicitly set.
+*/}}
+{{- if eq (typeOf $value) "map[string]interface {}" }}
+{{- merge (dict) $value (dict "name" $key) | list | toYaml | println }}
+{{- /*
+    - If extraEnv.someKey has a string value, then we use the key as the
+      environment variable name for the value.
+*/}}
+{{- else if eq (typeOf $value) "string" -}}
+- name: {{ $key | quote }}
+  value: {{ $value | quote | println }}
+{{- else }}
+{{- printf "?.extraEnv.%s had an unexpected type (%s)" $key (typeOf $value) | fail }}
+{{- end }}
+{{- end }} {{- /* end of range */}}
+{{- end }}
+{{- end }} {{- /* end of: if . */}}
+{{- end }} {{- /* end of definition */}}

jupyterhub/templates/hub/deployment.yaml

@@ -202,19 +202,7 @@ spec:
                   key: hub.db.password
             {{- end }}
             {{- end }}
-            {{- if .Values.hub.extraEnv }}
-            {{- $extraEnvType := typeOf .Values.hub.extraEnv }}
-            {{- /* If we have a list, embed that here directly. This allows for complex configuration from configmap, downward API, etc. */}}
-            {{- if eq $extraEnvType "[]interface {}" }}
-            {{- .Values.hub.extraEnv | toYaml | trimSuffix "\n" | nindent 12 }}
-            {{- else if eq $extraEnvType "map[string]interface {}" }}
-            {{- /* If we have a map, treat those as key-value pairs. */}}
-            {{- range $key, $value := .Values.hub.extraEnv }}
-            - name: {{ $key | quote }}
-              value: {{ $value | quote }}
-            {{- end }}
-            {{- end }}
-            {{- end }}
+            {{- include "jupyterhub.extraEnv" .Values.hub.extraEnv | nindent 12 }}
           ports:
             - containerPort: 8081
               name: hub