Dashboard: Handle Kubernetes API server failover

[mxey]

Environment

Dashboard version: v1.8.3
Kubernetes version: v1.10.2
Operating system: CentOS Linux release 7.4.1708 (Core)

Steps to reproduce

1. Have a multi-master Kubernetes cluster
2. Run dashboard with in-cluster config
3. Stop one of the API servers

Observed result

• Dashboard hangs while trying to load cluster resources, until Linux eventually timeouts the TCP connection.
• The dashboard pod is not killed and restarted automatically either, because the liveness probe does not exercise the Kubernetes API connection
• Even after the TCP timeout and eventual reconnect, the log still repeatedly shows Synchronizer kubernetes-dashboard-key-holder-kube-system exited with error: kubernetes-dashboard-key-holder-kube-system watch ended with timeout (see https://github.com/kubernetes/dashboard/issues/2723#issuecomment-382378523)

Expected result

• Dashboard has a shorter timeout on the API server connection and reconnects (might depend on https://github.com/kubernetes/client-go/issues/374)
• The dashboard has a liveness probe that actually tests core functionality of the dashboard (/api/v1/settings/global might do, but ideally a designated health URI)

[mjeri]

I just experienced the same issue. The dashboard was trying to synchronize in a fast loop (thousands of log entries in one second) consuming a lot of CPU.

[vdboor]

Even with a single-master cluster this happens.

Steps to reproduce:

• Run the dashboard (e.g. with default configuration from the helm chart)
• Restart the API server (find with kubectl get pods -n kube-system -l component=kube-apiserver)

The logging flood stops when the dashboard pod is deleted/recreated.

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[vdboor]

/remove-lifecycle stale

[maciaszczykm]

/lifecycle frozen

[Zenlil]

Same problem.

Running Azure AKS
K8 version 1.11.4 and 1.11.5
Dashboard image: k8s.gcr.io/kubernetes-dashboard-amd64:v1.10.0

After "Microsoft" sometimes restarts the managed API-server the dashboard starts to log around 450 lines per 5 minutes.

Any update on actually getting the reconnect solved?

[floreks]

@Zenlil it will be fixed in v2. Right now a workaround is to delete Dashboard pod after api server restart.

[WhoAteDaCake]

Still happening in 1.10.1 ? I was flodded with gigs of logs in no time. Deleting the dashboard pod did not solve it

[floreks]

Can you upload beginning of the log? First 30m let's say.

[spingel]

These are the initial log entries that we saw when we encountered the issue:

2019/07/26 02:28:58 Synchronizer kubernetes-dashboard-key-holder-kube-system exited with error: unexpected object: &Secret{ObjectMeta:k8s_io_apimachinery_pkg_apis_meta_v1.ObjectMeta{Name:,GenerateName:,Namespace:,SelfLink:,UID:,ResourceVersion:,Generation:0,CreationTimestamp:0001-01-01 00:00:00 +0000 UTC,DeletionTimestamp:<nil>,DeletionGracePeriodSeconds:nil,Labels:map[string]string{},Annotations:map[string]string{},OwnerReferences:[],Finalizers:[],ClusterName:,Initializers:nil,},Data:map[string][]byte{},Type:,StringData:map[string]string{},}

2019/07/26 02:29:00 Restarting synchronizer: kubernetes-dashboard-key-holder-kube-system.

2019/07/26 02:29:00 Starting secret synchronizer for kubernetes-dashboard-key-holder in namespace kube-system

2019/07/26 02:29:00 Synchronizer kubernetes-dashboard-key-holder-kube-system exited with error: kubernetes-dashboard-key-holder-kube-system watch ended with timeout

2019/07/26 02:29:02 Restarting synchronizer: kubernetes-dashboard-key-holder-kube-system.

2019/07/26 02:29:02 Starting secret synchronizer for kubernetes-dashboard-key-holder in namespace kube-system

2019/07/26 02:29:02 Synchronizer kubernetes-dashboard-key-holder-kube-system exited with error: kubernetes-dashboard-key-holder-kube-system watch ended with timeout

The last 3 errors repeat every 2 seconds causing a flood of log entries.

[floreks]

It's no longer a case with v2 as it forces restart of the pod after few retries.