External Autodiscovery plugin

[olblak]

This discussion is about getting feedback on the Updatecli external autodiscovery plugin feature.
It's still experimental, and we need as much feedback as possible to confidently move it to stable without future breaking changes

Problem

Defining update strategies in YAML is convenient, saves time, and helps teams collaborate. But when update rules grow complex, a small DSL can become limiting. Recently, we explored using WASM to let teams write manifest generators in the language they prefer. The feature is still experimental, and we welcome feedback from teams with complex update scenarios.

Solutions

Plugins can be written in any language that compiles to WebAssembly (WASM). We explored using the Extism framework.

We implemented on the Updatecli side this pull request:

• #7034

And an example of a custom plugin named demo.

A plugin must export the function _start (WASI). It is expected to receive a JSON object as input and return a JSON object containing the generated Updatecli manifests.

Input

A plugin receives a JSON object with the following fields:

{
  "scmid": "default",
  "actionid": "default",
  "rootdir"": "current directory"
  "spec": {
    "plugin_param1": "",
    "plugin_param2": ""
  }
}

The scmid field is provided by Updatecli, it's up to the plugin maintainer to decide how to use that information, but typically it's used to link resources to a scm configuration specified in the Updatecli manifest.

The actionid field is provided by Updatecli, it's up to the plugin maintainer to decide how to use that information but typically it's used to specify an action title.

The spec field is the plugin parameters detected by Updatecli.

Output

A plugin must output a JSON object such as

{
  "manifests": [
    "Updatecli manifest 1",
    "Updatecli manifest 2"
  ]
}

Where manifests contains the list of generated Updatecli manifests

Guidelines:

• Include a version field in generated manifests to indicate the minimum Updatecli version required.
• Do not set pipelineid in generated manifests (Updatecli overrides it).

Improvement

• Right now the plugin must remain local to the Updatecli manifest file, it would be nice to also support fetching plugins from an OCI registry.