The listener is a Linux-only binary. In mixed-OS clusters (e.g. with
Windows node pools), the listener pod can be scheduled on a Windows
node where it fails with a platform mismatch.
Issue #2652 was closed by #2758 which gave users a workaround via
listenerTemplate, but the default behavior still allows the listener
to be scheduled on Windows nodes. This PR adds a safe default
(kubernetes.io/os: linux) so users don't need to explicitly configure
listenerTemplate just to prevent the listener from landing on a
non-Linux node.
Changes:
- Add default nodeSelector kubernetes.io/os: linux to listener pod spec
- Define LabelKeyKubernetesOS constant alongside existing k8s labels
- Make mergeListenerPodWithTemplate preserve the default when the
listenerTemplate does not explicitly set a nodeSelector (nil check)
- Add unit tests for all nodeSelector merge scenarios
Refs: #2652
ac64be27d5