I've created a 3 nodes GKE cluster which is running fine but I noticed a few times that my components are not able to reach the API Server during 3 or 4 minutes.
I recently had the same problem again on a fresh new cluster so I decided to look a bit closer. In the Compute Engine Operations section I noticed at the same time that the 3 routes had been removed and recreated 4 minutes later... This task had been scheduled by a @cloudservices.gserviceaccount.com address so from the cluster directly I suppose.
What is causing this behavior, forcing the routes to be deleted and recreated randomly ?
The apiserver may become unreachable if it gets temporarily overloaded or if it is upgraded or repaired. This should be unrelated to routes being removed and recreated, although it's possible that the node manager does not behave correctly when it is restarted.