[shell-operator] fix: protect shared informer lifecycle

[fuldaxxx]

Overview

Fix a shared-informer lifecycle bug in FactoryStore (pkg/kube_events_manager/factory.go).
A shared informer is a long-lived, store-owned resource, but its context used to be
derived from the first consumer that registered it. Cancelling that consumer's
context (e.g. when its monitor is stopped during a module reload) tore down the shared
informer for every other consumer still using it, silently freezing their snapshots
until the process was restarted. Ownership of the informer lifetime is moved to the
store, plus three supporting fixes (dead-factory detection, a narrower critical section,
and an un-swallowed error).

What this PR does / why we need it

Root cause. NewFactoryStore() did not receive a context, and add() derived the
factory context via context.WithCancel(ctx) from the caller's context. The chain
mgr.ctx → monitor.ctx → resourceInformer.ei.ctx → Start(ei.ctx) → add(ei.ctx) meant
factory.ctx was a child of the ei.ctx of whichever monitor created the factory first.
Because factories are shared across monitors with the same FactoryIndex
(GVR + namespace + selectors), stopping that first monitor cancelled the shared informer
for all remaining consumers, while the refcount (handlerRegistrations) was still > 0 so
the factory stayed cached. The surviving consumers were left attached to a dead informer.

This is a classic ownership bug: the lifetime of a shared, long-lived resource must be
owned by the store, not inherited from a transient consumer.

Impact. The failure is silent (no error, HasSynced() on a stopped-but-once-synced
informer returns true) and only recoverable by restarting the process. In
surfaced as an empty DexClient snapshot in user-authn: the hook feeds the desired
object list into values, Helm prunes anything not in the list, so an empty
to the dex-client-* Secret and OAuth2Client being deleted — breaking OIDC login to
the cluster. Mass module reloads (e.g. during an upgrade) are the trigger w

Special notes for your reviewer

[Copilot]

Pull request overview

Fixes a shared-informer lifecycle/ownership bug in FactoryStore so that shared informers are anchored to the events-manager/store lifetime rather than the first consumer’s context, preventing other consumers’ snapshots from silently freezing when that first consumer is stopped.

Changes:

• Make FactoryStore context-aware (baseCtx) and derive factory/informer contexts from the store instead of from the first registering consumer.
• Add dead-factory detection/recreation, narrow the store lock critical section during initial sync, and stop silently swallowing a watch error handler registration error.
• Add targeted tests covering the shared-informer lifetime, shutdown waiting behavior, and dead-factory recreation.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
pkg/kube_events_manager/monitor_test.go	Updates monitor test setup to pass a context into NewFactoryStore.
pkg/kube_events_manager/kube_events_manager.go	Anchors the factory store lifetime to the manager context.
pkg/kube_events_manager/factory.go	Reworks shared informer lifecycle ownership and improves concurrency/liveness handling.
pkg/kube_events_manager/factory_test.go	Adds regression tests for shared informer ownership, WaitStopped, and dead-factory recreation.

Comments suppressed due to low confidence (1)

pkg/kube_events_manager/factory.go:158

• Start logs AddEventHandler errors but continues, still recording the (possibly nil) registration and returning nil to the caller. This can leave a broken handler entry and makes failures invisible to resourceInformer.start(). Consider returning the error (after releasing c.mu) so the caller can handle it and Stop won’t later try to remove a nil registration.

	registration, err := informer.AddEventHandler(handler)
	if err != nil {
		log.Warn("Factory store: couldn't add event handler to the factory's informer",
			slog.String(pkg.LogKeyNamespace, index.Namespace), slog.String(pkg.LogKeyGVR, index.GVR.String()),
			log.Err(err))

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[fuldaxxx]

done