How to use ExtensionServiceConfig for custom Extensions?

[PJ-Schulz]

The documentation docs has so many gaps, or rather, it doesn't describe anything at all, and I've been searching through all the issues/discussions/pull requests and other repositories for days, but I still don't know exactly how to use ExtensionServiceConfig for my own custom extension.

---

Until now, the configurations for our custom extensions have always been stored under machine.files[], here is an example:

machine:
  files:
  - content: |
      {
      "cert_ttl_sec": 2592000,
      "renewal_interval_sec": 3600
      }
    op: create
    path: /var/extension-data/foo-ext/config.json
    permissions: 0o600

And our extension depends on this file:

name: foo-ext
container:
  entrypoint: /usr/bin/python3
  args: 
    - /app/main.py
  mounts:
    - source: /var/extension-data/foo-ext
      destination: /extension-data/foo-ext
      type: bind
      options:
        - rshared
        - rbind
        - rw
depends:
  - path: /var/extension-data/foo-ext/config.json
restart: always

---

How should this now be done with ExtensionServiceConfig?

This is my Extension file:

name: foo-ext
container:
  entrypoint: /usr/bin/python3
  args: 
    - /app/main.py
  mounts:
    - source: /var/extension-data/foo-ext
      destination: /extension-data/foo-ext
      type: bind
      options:
        - rshared
        - rbind
        - rw
depends:
  - configuration: true  # <-- This is needed to say Talos that an ExtensionServiceConfig is needed for this Extension
restart: always

And this is my ExtensionServiceConfig:

apiVersion: v1alpha1
kind: ExtensionServiceConfig
name: foo-ext
configFiles:
  - content: |
      {
      "cert_ttl_sec": 2592000,
      "renewal_interval_sec": 3800
      }
    mountPath: /var/extension-data/foo-ext/config.json

But when I apply it, my extension crashes because it cannot find the file /extension-data/foo-ext/config.json.

And when I try to show me the file with talosctl list /var/extension-data/foo-ext, I can not see it.

So what is the correct way?

---

Summary what I've done:

1. changed the depends from - path: /var/extension-data/foo-ext/config.json to - configuration: true in my Extension definiton
2. removed the file from machine.files and use the ExtensionServiceConfig resource, with the same content and path in my machine configuration

Talos version: 1.10.6

[frezbo]

when using ExtensionServiceConfig the app yaml definition doesn't need a mount at all, the extensionservice config adds that at runtime.

The ExtensionServiceConfig name should be just foo not foo-ext

[PJ-Schulz]

Thanks, removing the mount works.

For other users with the same problem, ths is now the new Extension Service config file:

name: foo-ext
container:
  entrypoint: /usr/bin/python3
  args: 
    - /app/main.py
depends:
  - configuration: true  # <-- This is needed to say Talos that an ExtensionServiceConfig is needed for this Extension
restart: always

So the content of ExtensionServiceConfig configFiles are mounted directly into the extension service container, rather than being placed on the disk as I had assumed, where a manual mount is needed like with the machine.files[].

I think it would be helpful if the documentation for ExtensionServiceConfig were expanded to include how to use it to configure an extension.

[frezbo]

PR's are welcome ❤️