KCP waiting on remote cluster client hangs worker, substantially delaying cluster deletion

[randomvariable]

What steps did you take and what happened:
[A clear and concise description on how to REPRODUCE the bug.]

In CAPV, I created a new cluster, followed by deleting it. Under the default of 1 worker, KCP controller will seemingly hang after the machines are deleted, eventually printing (I have added some extra log lines in my branch to trace what's going on):

[manager] I0310 08:30:06.521810       8 controller.go:171] controller-runtime/controller "msg"="Starting Controller"  "controller"="kubeadmcontrolplane"
[manager] I0310 08:30:06.521864       8 controller.go:190] controller-runtime/controller "msg"="Starting workers"  "controller"="kubeadmcontrolplane" "worker count"=1
[manager] I0310 08:31:05.532426       8 kubeadm_control_plane_controller.go:733] controllers/KubeadmControlPlane "msg"="deleting control plane, checking for machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:31:05.532479       8 kubeadm_control_plane_controller.go:739] controllers/KubeadmControlPlane "msg"="filtering machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:31:05.532492       8 kubeadm_control_plane_controller.go:751] controllers/KubeadmControlPlane "msg"="Non control plane machines exist and must be removed before control plane machines are removed" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:31:35.685832       8 kubeadm_control_plane_controller.go:733] controllers/KubeadmControlPlane "msg"="deleting control plane, checking for machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:31:35.685914       8 kubeadm_control_plane_controller.go:739] controllers/KubeadmControlPlane "msg"="filtering machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:31:48.434291       8 kubeadm_control_plane_controller.go:173] controllers/KubeadmControlPlane "msg"="Failed to update KubeadmControlPlane Status" "error"="etcdserver: request timed out" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:31:48.434861       8 controller.go:258] controller-runtime/controller "msg"="Reconciler error" "error"="etcdserver: request timed out"  "controller"="kubeadmcontrolplane" "request"={"Namespace":"default","Name":"test"}
[manager] I0310 08:31:49.435353       8 kubeadm_control_plane_controller.go:733] controllers/KubeadmControlPlane "msg"="deleting control plane, checking for machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:31:49.435468       8 kubeadm_control_plane_controller.go:739] controllers/KubeadmControlPlane "msg"="filtering machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:32:02.432420       8 kubeadm_control_plane_controller.go:173] controllers/KubeadmControlPlane "msg"="Failed to update KubeadmControlPlane Status" "error"="etcdserver: request timed out" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:32:02.440652       8 controller.go:258] controller-runtime/controller "msg"="Reconciler error" "error"="etcdserver: request timed out"  "controller"="kubeadmcontrolplane" "request"={"Namespace":"default","Name":"test"}
[manager] I0310 08:32:03.441244       8 kubeadm_control_plane_controller.go:733] controllers/KubeadmControlPlane "msg"="deleting control plane, checking for machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:32:03.441342       8 kubeadm_control_plane_controller.go:739] controllers/KubeadmControlPlane "msg"="filtering machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:32:16.436936       8 kubeadm_control_plane_controller.go:173] controllers/KubeadmControlPlane "msg"="Failed to update KubeadmControlPlane Status" "error"="etcdserver: request timed out" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:32:16.437515       8 controller.go:258] controller-runtime/controller "msg"="Reconciler error" "error"="etcdserver: request timed out"  "controller"="kubeadmcontrolplane" "request"={"Namespace":"default","Name":"test"}
[manager] I0310 08:32:17.437983       8 kubeadm_control_plane_controller.go:733] controllers/KubeadmControlPlane "msg"="deleting control plane, checking for machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:32:17.438080       8 kubeadm_control_plane_controller.go:739] controllers/KubeadmControlPlane "msg"="filtering machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:37:19.961771       8 kubeadm_control_plane_controller.go:173] controllers/KubeadmControlPlane "msg"="Failed to update KubeadmControlPlane Status" "error"="Get \"https://192.168.192.187:6443/api/v1/nodes?labelSelector=node-role.kubernetes.io%2Fmaster%3D\": read tcp 10.244.0.31:34044-\u003e192.168.192.187:6443: read: connection timed out" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:37:19.962149       8 controller.go:258] controller-runtime/controller "msg"="Reconciler error" "error"="Get \"https://192.168.192.187:6443/api/v1/nodes?labelSelector=node-role.kubernetes.io%2Fmaster%3D\": read tcp 10.244.0.31:34044-\u003e192.168.192.187:6443: read: connection timed out"  "controller"="kubeadmcontrolplane" "request"={"Namespace":"default","Name":"test"}
[manager] I0310 08:37:20.962520       8 kubeadm_control_plane_controller.go:733] controllers/KubeadmControlPlane "msg"="deleting control plane, checking for machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:37:20.962614       8 kubeadm_control_plane_controller.go:739] controllers/KubeadmControlPlane "msg"="filtering machines" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] I0310 08:37:20.962639       8 kubeadm_control_plane_controller.go:744] controllers/KubeadmControlPlane "msg"="no machines, ok to delete" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:37:22.953251       8 kubeadm_control_plane_controller.go:173] controllers/KubeadmControlPlane "msg"="Failed to update KubeadmControlPlane Status" "error"="failed to create remote cluster client: failed to create client for Cluster default/test: Get \"https://192.168.192.187:6443/api?timeout=32s\": dial tcp 192.168.192.187:6443: connect: no route to host" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:37:22.986688       8 kubeadm_control_plane_controller.go:179] controllers/KubeadmControlPlane "msg"="Failed to patch KubeadmControlPlane" "error"="kubeadmcontrolplanes.controlplane.cluster.x-k8s.io \"test\" not found" "cluster"="test" "kubeadmControlPlane"="test" "namespace"="default" 
[manager] E0310 08:37:22.986769       8 controller.go:258] controller-runtime/controller "msg"="Reconciler error" "error"="[failed to create remote cluster client: failed to create client for Cluster default/test: Get \"https://192.168.192.187:6443/api?timeout=32s\": dial tcp 192.168.192.187:6443: connect: no route to host, kubeadmcontrolplanes.controlplane.cluster.x-k8s.io \"test\" not found]"  "controller"="kubeadmcontrolplane" "request"=

What did you expect to happen:
Resources to be deleted within 60s.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]
Increasing workers would be a suitable workaround for now. Finding a way to synchronise on a channel and cancel outstanding reconciliations on delete is maybe one potential optimisation.

Environment:

• Cluster-api version: 0.3.0-rc.3
• Minikube/KIND version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

/kind bug

[detiber]

I wonder if it would make sense to move the deferred call to r.updateStatus after the call to r.reconcileDelete in Reconcile.

[detiber]

We should probably also increase the default concurrency on KubeadmControlPlane reconciliation 😂

[detiber]

I don't necessarily think either of the fixes above are necessarily release blockers for v0.3.0, but are definitely candidates for a fast-follow patch release.

[vincepri]

/milestone v0.3.x

[chuckha]

Increasing default concurrency is a different problem and won't help in this case, but +1 on increasing it to 10 regardless.

The reason it won't help is that increasing a controller's concurrency will still only reconcile each object serially and not reconcile the same object concurrently. Since each cluster only has one KCP resource, the hanging is still a problem. This will, however, improve the situation when there are multiple control planes being managed by this controller.

I'm +1 on adding some concurrency within the control loop. Probably 1 go routine for each delete (== 1 go routine / node) sounds pretty reasonable. This would be similar to what we had originally (before health checks).

[detiber]

The concurrency comment was more of an aside. I do think we need to consider moving the call to updateStatus to a defer that is configured after reconcileDelete has been processed. If we still need a status update during reconcileDelete, we can probably add an additional defer for it to reconcileDelete where we can add more safety around failures communicating with the workload cluster.

[wfernandes]

I'm thinking of investigating this further. Has anyone seen this behavior with CAPA?
Asking because I do not have access to any vSphere infrastructure and was going to see if I can reproduce this with CAPA.

[detiber]

@wfernandes you should be able to replicate by attempting to delete prior to the first control plane Machine becoming ready.

[wfernandes]

/assign

[wfernandes]

/lifecycle active

[wfernandes]

It seems that this issue was fixed as part of this PR: #2708.
/close

[k8s-ci-robot]

@wfernandes: Closing this issue.

In response to this:

It seems that this issue was fixed as part of this PR: #2708.
/close

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