[RELEASE-0.21][Backport] Unregister views to avoid slow oom issue during meter cleanup

vendor/knative.dev/pkg/metrics/resource_view.go

@@ -82,10 +82,16 @@ func cleanup() {
 	expiryCutoff := allMeters.clock.Now().Add(-1 * maxMeterExporterAge)
 	allMeters.lock.Lock()
 	defer allMeters.lock.Unlock()
+	resourceViews.lock.Lock()
+	defer resourceViews.lock.Unlock()
 	for key, meter := range allMeters.meters {
 		if key != "" && meter.t.Before(expiryCutoff) {
 			flushGivenExporter(meter.e)
+			// Make a copy of views to avoid data races
+			viewsCopy := copyViews(resourceViews.views)
+			meter.m.Unregister(viewsCopy...)
 			delete(allMeters.meters, key)
+			meter.m.Stop()
 		}
 	}
 }
@@ -139,7 +145,7 @@ func RegisterResourceView(views ...*view.View) error {
 	return nil
 }
 
-// UnregisterResourceView is similar to view.Unregiste(), except that it will
+// UnregisterResourceView is similar to view.Unregister(), except that it will
 // unregister the view across all Resources tracked byt he system, rather than
 // simply the default view.
 func UnregisterResourceView(views ...*view.View) {