File states never get deleted from the filestream registry

[rdner]

Instead of using the delete operation the current implementation sets TTL to 0 instead.

beats/filebeat/input/filestream/internal/input-logfile/store.go

Lines 381 to 388 in 5d974fd

	func (s *store) remove(key string) error {
	resource := s.ephemeralStore.Find(key, false)
	if resource == nil {
	return fmt.Errorf("resource '%s' not found", key)
	}
	s.UpdateTTL(resource, 0)
	return nil
	}

I suppose the intention was to optimise the deletion process and delay it until some kind of garbage collection.

However when we delete files:

1. We retain their states in-memory (might be even until next restart)
2. We make another set operation record in the registry log, which is much larger than the delete operation line

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[belimawr]

I was looking into a similar issue, but from another perspective and ended up opening #36761. The TTL might not be the issue here. Anyway because they could be different, I ended up opening the new issue.

[rdner]

Re-assigning to @belimawr since he already has a fixing PR open.