add spec.observer (auto|none) and wire to router

[AryanP123]

Fixes #2342

Testing:

$ kubectl -n skupper patch listener test-tcp --type=merge -p '{"spec":{"observer":"none"}}' listener.skupper.io/test-tcp patched (no change)

$ kubectl -n skupper patch listener test-tcp --type=merge -p '{"spec":{"observer":"non"}}' The Listener "test-tcp" is invalid: spec.observer: Unsupported value: "non": supported values: "auto", "none"

$ kubectl -n skupper get cm -o json \ | jq -r '.items[]|select(.data)|.data[]|select(test("tcpListener"))' \ | grep -A12 '"name": "test-tcp"' "name": "test-tcp", "port": "1024", "address": "backend", "siteId": "7e9ba960-e605-4f9a-8b1b-0cc5f5d0b6da", "observer": "none" } ] ]

[nluaces]

LGTM!

Checked that the listener has the expected observer type in the router config:

$ skmanage query --type tcpListener
[
  {
    "address": "database",
    "host": "",
    "backlog": 0,
    "port": "1024",
    "siteId": "f77ac22c-0e6b-49d1-b9b9-c3fe1ca031fb",
    "connectionsOpened": 0,
    "connectionsClosed": 0,
    "bytesIn": 0,
    "bytesOut": 0,
    "authenticatePeer": false,
    "operStatus": "down",
    "connectionMsg": "",
    "observer": "auto",
    "name": "database",
    "identity": "tcpListener/:1024:database",
    "type": "io.skupper.router.tcpListener"
  }
]

I propose to wait for @c-kruse approval before merging this PR.

[c-kruse]

Router configuration looks solid to me! Now on to the API and docs.

[c-kruse]

We should review how we plan to expose this option to users as a larger group.

To me an optional field with an enum of auto/none strongly indicates a boolean flag like disableObserver. That said, that does not help users pick a specific observer like http1 or http2 (or any future implementations.)

The description also needs to explain what the observer is and what the implications of setting it are. I would suggest we lean on @pwright and @ted-ross for help in this department.

[pwright]

My attempt at required docs (one piece for user guide, another for migration):
https://gist.github.com/pwright/d0916a452e5eb170f410d3ad8428765b

[c-kruse]

Suggested change

	description: Control protocol observation for this listener. Default 'auto'. Use 'none' to disable, or 'http1'/'http2' to force a specific observer.
	description: |-
	The listener observer controls how the listener inspects network traffic for application protocol information. When unset or set to `auto` the listener inspects traffic for known application protocols and produces telemetry events for that application traffic. Set to a specific protocol, `http1` or `http2`, to only inspect traffic for that particular protocol. Set to `none` to disable the observer and reduce overhead from traffic inspection and application level telemetry.

Probably needs some formatting and a 👍 from @pwright

[pwright]

submitted my suggestion, mostly C's text

[pwright]

consider updating desc

[pwright]

Proposed Release Note:

Protocol inspection

You can now control application-level protocol inspection on listener traffic using the new spec.observer field on the Listener custom resource. This field supports automatic protocol detection (auto, default), forcing inspection to http1 or http2, or disabling inspection entirely with none to reduce traffic inspection overhead and application-level telemetry.