My love hate relationship with k8s continues

Alex Schiessl's photo
Alex Schiessl

Published on Sep 25, 2021

7 min read

Yup, another chapter in my love hate relationship is topic of this blog post.

So, a few days ago, exactly on the morning of my birthday, I wanted to check the temperature at my node-red driven Weather panel. But, "page cannot be found"! So, naturally I thought "WTF, come on it is my birthday"! Never the less I made coffee and checked what's going on.

Soon I found out, k3s on k3os - yes, I run k3s on k3os, which itself is an takeover installation of ubuntu, which is the only way I got k3os on my Raspi 4B+, cause I couldn't get k3os to boot on the Raspi. Anyway back to topic.

Ok, so naturally I tried to use portainer, since it is my lightweight choice for k8s management. It was not working, so I ssh'ed into my k3os-server and did the natural thing "kubectl get pods -A". So k3s was running, but most of the pods which I needed, node-red, portainer, elk where not running, they where pending. It looked like this:

k3os-server [~]$ kubectl get pods -A
NAMESPACE        NAME                                                              READY   STATUS     RESTARTS   AGE
elk              kibana-kibana-54c46c54d6-nx9nr                                    0/1     Pending    0          13h
elk              logstash-logstash-0                                               0/1     Pending    0          13h
portainer        portainer-agent-5988b5d966-5cgkz                                  0/1     Pending    0          3h45m
elk              elasticsearch-master-0                                            0/1     Running    3          13h
portainer        svclb-portainer-agent-9xssw                                       1/1     Running    2          3h43m
elk              svclb-logstash-logstash-47ksf                                     1/1     Running    3          13h
elk              svclb-kibana-kibana-8wp5z                                         1/1     Running    3          13h
node-red      node-red-6678875c4c-cxgpk                   0/1     Running       3          3h45m
kube-system      svclb-traefik-lqcr7                                               2/2     Running    4          3h51m
k3os-system      system-upgrade-controller-8bf4f84c4-dwmnv                         1/1     Running    14         78d
k3os-system      apply-k3os-latest-on-k3os-server-with-de0d67248001a3a3b02-8bppd   0/1     Init:1/2   0          9m9s
kube-system      metrics-server-7566d596c8-rpx6w                                   0/1     Pending    0          107s
kube-system      traefik-56f7bf7775-wsjb6                                          0/1     Pending    0          74s
kube-system      local-path-provisioner-64d457c485-pv9w4                           0/1     Pending    0          61s
kube-system      coredns-5d69dc75db-7jln6                                          0/1     Pending    0          47s
system-upgrade   system-upgrade-controller-85b58fbc5f-xft58                        0/1     Pending    0          3s

So I tried with "kubectl describe pod/portainer-agent-5988b5d966-5cgkz -n portainer" to figure out, why portainer was not working. This was the output:

k3os-server [~]$ kubectl describe pod/portainer-agent-5988b5d966-5cgkz -n portainer
Name:           portainer-agent-5988b5d966-5cgkz
Namespace:      portainer
Priority:       0
Node:           <none>
Labels:         app=portainer-agent
                pod-template-hash=5988b5d966
Annotations:    <none>
Status:         Pending
IP:
IPs:            <none>
Controlled By:  ReplicaSet/portainer-agent-5988b5d966
Containers:
  portainer-agent:
    Image:      portainer/agent:latest
    Port:       9001/TCP
    Host Port:  0/TCP
    Environment:
      LOG_LEVEL:           DEBUG
      AGENT_CLUSTER_ADDR:  portainer-agent-headless
      KUBERNETES_POD_IP:    (v1:status.podIP)
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from portainer-sa-clusteradmin-token-zdg7s (ro)
Conditions:
  Type           Status
  PodScheduled   False
Volumes:
  portainer-sa-clusteradmin-token-zdg7s:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  portainer-sa-clusteradmin-token-zdg7s
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                 node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type     Reason            Age   From               Message
  ----     ------            ----  ----               -------
  Warning  FailedScheduling  92m   default-scheduler  0/1 nodes are available: 1 node(s) were unschedulable.

Ok, there was a glue: "unschedulable". Aha! So I did the next logical thing, at least for me, I entered "kubectl get node" and the output was:

k3os-server [~]$ kubectl get node
NAME          STATUS                     ROLES                  AGE    VERSION
k3os-server   Ready,SchedulingDisabled   control-plane,master   233d   v1.19.15+k3s1

Aha! "Ready,SchedulingDisabled". So I was confused why was scheduling disabled. So naturally I checked k3os on github. And of course a new version was released. So I immediately suspected the Auto Upgrade Feature. So I mad sure, auto upgrade was configured right, rebooted and waited 30min, while I was finally getting my breakfast. But when I checked again, no success, still same output.

Well, so I did another thing most of you have done before. Stackoverflow to the rescue. There I found this little line:

k3os-server [~]$ kubectl patch node k3os-server -p "{\"spec\":{\"unschedulable\":false}}"

So I made sure, that my server was tainted "unschedulable"

k3os-server [~]$ kubectl describe node
Name:               k3os-server
Roles:              control-plane,master
Labels:             beta.kubernetes.io/arch=arm64
                    beta.kubernetes.io/instance-type=k3s
                    beta.kubernetes.io/os=linux
                    k3os.io/mode=local
                    k3os.io/upgrade=enabled
                    k3os.io/version=v0.19.15-k3s1r0
                    k3s-upgrade=true
                    k3s.io/hostname=k3os-server
                    k3s.io/internal-ip=192.168.0.7
                    kubernetes.io/arch=arm64
                    kubernetes.io/hostname=k3os-server
                    kubernetes.io/os=linux
                    node-role.kubernetes.io/control-plane=true
                    node-role.kubernetes.io/master=true
                    node.kubernetes.io/instance-type=k3s
                    plan.upgrade.cattle.io/k3os-latest=ac5fabe1f913dcad262a3c711eba31016d3297ac24d3db12f8daaa8d
Annotations:        flannel.alpha.coreos.com/backend-data: {"VtepMAC":"4a:a8:ea:c2:69:6c"}
                    flannel.alpha.coreos.com/backend-type: vxlan
                    flannel.alpha.coreos.com/kube-subnet-manager: true
                    flannel.alpha.coreos.com/public-ip: 192.168.0.7
                    k3s.io/node-args:
                      ["server","--node-label","k3os.io/upgrade=enabled","--node-label","k3os.io/mode=local","--node-label","k3os.io/version=v0.19.15-k3s1r0"]
                    k3s.io/node-config-hash: UVUEL5HG5BTFEVR6MMGXJKHXJDX6XUREL7WJWDOM3IRLYCPS7JAQ====
                    k3s.io/node-env:
                      {"K3S_CLUSTER_SECRET":"********","K3S_DATA_DIR":"/var/lib/rancher/k3s/data/dcd31a7b8a5c2021f385fc354f38fe7b3fb758660905ed62a0faf7307e701fe...
                    node.alpha.kubernetes.io/ttl: 0
                    volumes.kubernetes.io/controller-managed-attach-detach: true
CreationTimestamp:  Tue, 02 Feb 2021 12:23:32 +0000
Taints:             node.kubernetes.io/unschedulable:NoSchedule
Unschedulable:      true
Lease:
  HolderIdentity:  k3os-server
  AcquireTime:     <unset>
  RenewTime:       Thu, 23 Sep 2021 10:23:30 +0000
Conditions:
  Type                 Status  LastHeartbeatTime                 LastTransitionTime                Reason                       Message
  ----                 ------  -----------------                 ------------------                ------                       -------
  NetworkUnavailable   False   Thu, 23 Sep 2021 08:48:26 +0000   Thu, 23 Sep 2021 08:48:26 +0000   FlannelIsUp                  Flannel is running on this node
  MemoryPressure       False   Thu, 23 Sep 2021 10:18:47 +0000   Tue, 02 Feb 2021 12:23:32 +0000   KubeletHasSufficientMemory   kubelet has sufficient memory available
  DiskPressure         False   Thu, 23 Sep 2021 10:18:47 +0000   Tue, 02 Feb 2021 12:23:32 +0000   KubeletHasNoDiskPressure     kubelet has no disk pressure
  PIDPressure          False   Thu, 23 Sep 2021 10:18:47 +0000   Tue, 02 Feb 2021 12:23:32 +0000   KubeletHasSufficientPID      kubelet has sufficient PID available
  Ready                True    Thu, 23 Sep 2021 10:18:47 +0000   Thu, 23 Sep 2021 08:48:41 +0000   KubeletReady                 kubelet is posting ready status
Addresses:
  InternalIP:  192.168.0.7
  Hostname:    k3os-server
Capacity:
  cpu:                4
  ephemeral-storage:  153593272Ki
  memory:             7997752Ki
  pods:               110
Allocatable:
  cpu:                4
  ephemeral-storage:  149415534885
  memory:             7997752Ki
  pods:               110
System Info:
  Machine ID:                 47db285f8c257cdd3191ef3f614ce3ab
  System UUID:                47db285f8c257cdd3191ef3f614ce3ab
  Boot ID:                    259c932f-16d4-4674-8232-6b98edc4096c
  Kernel Version:             5.4.0-1028-raspi
  OS Image:                   k3OS v0.19.15-k3s1r0
  Operating System:           linux
  Architecture:               arm64
  Container Runtime Version:  containerd://1.4.9-k3s1
  Kubelet Version:            v1.19.15+k3s1
  Kube-Proxy Version:         v1.19.15+k3s1
PodCIDR:                      10.42.0.0/24
PodCIDRs:                     10.42.0.0/24
ProviderID:                   k3s://k3os-server
Non-terminated Pods:          (7 in total)
  Namespace                   Name                                                               CPU Requests  CPU Limits  Memory Requests  Memory Limits  AGE
  ---------                   ----                                                               ------------  ----------  ---------------  -------------  ---
  elk                         elasticsearch-master-0                                             1 (25%)       1 (25%)     2Gi (26%)        2Gi (26%)      13h
  portainer                   svclb-portainer-agent-9xssw                                        0 (0%)        0 (0%)      0 (0%)           0 (0%)         3h46m
  elk                         svclb-logstash-logstash-47ksf                                      0 (0%)        0 (0%)      0 (0%)           0 (0%)         13h
  elk                         svclb-kibana-kibana-8wp5z                                          0 (0%)        0 (0%)      0 (0%)           0 (0%)         13h
  kube-system                 svclb-traefik-lqcr7                                                0 (0%)        0 (0%)      0 (0%)           0 (0%)         3h54m
  k3os-system                 system-upgrade-controller-8bf4f84c4-dwmnv                          0 (0%)        0 (0%)      0 (0%)           0 (0%)         78d
  k3os-system                 apply-k3os-latest-on-k3os-server-with-de0d67248001a3a3b02-8bppd    0 (0%)        0 (0%)      0 (0%)           0 (0%)         12m
Allocated resources:
  (Total limits may be over 100 percent, i.e., overcommitted.)
  Resource           Requests   Limits
  --------           --------   ------
  cpu                1 (25%)    1 (25%)
  memory             2Gi (26%)  2Gi (26%)
  ephemeral-storage  0 (0%)     0 (0%)
Events:              <none>

And there it was "Taints: node.kubernetes.io/unschedulable:NoSchedule" Ok, I applied a fix I came up after reading an stackoverflow article and that was the result:

k3os-server [~]$ kubectl patch node k3os-server -p "{\"spec\":{\"unschedulable\":false}}"
node/k3os-server patched
k3os-server [~]$ kubectl get node
NAME          STATUS   ROLES                  AGE    VERSION
k3os-server   Ready    control-plane,master   233d   v1.19.15+k3s1

And of course a reboot. After some distractions, it was my birthday after all, I checked again, and the update was done and apps worked again:

k3os-server [~]$ kubectl get node
NAME          STATUS   ROLES                  AGE    VERSION
k3os-server   Ready    control-plane,master   233d   v1.20.11+k3s1
k3os-server [~]$ kubectl get pods -A
NAMESPACE     NAME                                        READY   STATUS    RESTARTS   AGE
elk           elasticsearch-master-0                      1/1     Running   0          44m
kube-system   metrics-server-86cbb8457f-hnnr7             1/1     Running   1          42m
kube-system   local-path-provisioner-5ff76fc89d-jqsqt     1/1     Running   2          42m
kube-system   coredns-6488c6fcc6-v6zs2                    1/1     Running   1          42m
k3os-system   system-upgrade-controller-c6c9b4c5d-6l8wq   1/1     Running   2          42m
kube-system   traefik-7b6b5b8795-6jxpn                    1/1     Running   0          40m
elk           svclb-kibana-kibana-9n7xg                   1/1     Running   0          40m
elk           svclb-logstash-logstash-gsmnb               1/1     Running   0          40m
portainer     svclb-portainer-agent-rtq8g                 1/1     Running   0          40m
kube-system   svclb-traefik-rzz6w                         2/2     Running   0          40m
portainer     portainer-agent-5988b5d966-jdjvb            1/1     Running   4          48m
elk           logstash-logstash-0                         1/1     Running   1          44m
elk           kibana-kibana-54c46c54d6-84g5k              1/1     Running   3          4m14s
node-red      node-red-68fd7b8bdd-d9s88                   1/1     Running       0          42m

To be honest I rather would have been spared by this "crisis", but it happened and I learned something from it. That's a good thing.And of course how valuable Stackoverflow is and it makes our live in I.T. so much easier.

But that brings me back to my love hate relationship. Why is it so hard to find the problems with k8s. I'm still not sure if what I did was ok, but it worked. That is what counts. But can I be sure it will not happen again, when the next update of k3os is released!? I don't know.

Of course it is k3s on a k3os, which is not the typical k8s environment, but I had a Pi and time and interest, so why not. And of course, the failure surely had something to do with me not liking how to configure k8s. And hence I surely did something wrong when I configured auto upgrade for k3os. For my defense I can only say it worked before, because at some point auto upgrade had to work otherwise it would have not upgraded to "v1.19.15+k3s1".

Anyhow, I don't think it is k3s or k3os which caused the problem, but at this point, I don't care. I simply want to see my temperature. :-)

Bildschirmfoto 2021-09-25 um 21.06.38.png

As always apply this rule: "Questions, feel free to ask. If you have ideas or find errors, mistakes, problems or other things which bother or enjoy you, use your common sense and be a self-reliant human being."

Have a good one. Alex

 
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