K3S: Do i need a virtual IP for server nodes when using HA mode?

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  I'm struggling with this cross-communication between pods even though clusterIP services are set up for them. All the pods are on the same master node, and in the same namespace. In Summary:

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  NAME                         READY   STATUS    RESTARTS   AGE    IP           NODE          NOMINATED NODE   READINESS GATES
  nginx-744f4df6df-rxhph       1/1     Running   0          136m   10.42.0.31   raspberrypi   <none>           <none>
  nginx-2-867f4f8859-csn48     1/1     Running   0          134m   10.42.0.32   raspberrypi   <none>           <none>
  
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  nginx-service    ClusterIP   10.43.155.201   <none>        80/TCP                       136m   app=nginx
  nginx-service2   ClusterIP   10.43.182.138   <none>        85/TCP                       134m   app=nginx-2
  

  where I can't curl http://nginx-service2:85 from within nginx container, or vice versa... while I validated that this worked from my docker desktop installation:

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  root@nginx-7dc45fbd74-7prml:/# curl http://nginx-service2:85
  <!DOCTYPE html>
  <html>
  <head>
  <title>Welcome to nginx!</title>
  <style>
      body {
          width: 35em;
          margin: 0 auto;
          font-family: Tahoma, Verdana, Arial, sans-serif;
      }
  </style>
  </head>
  <body>
  <h1>Welcome to nginx!</h1>
  <p>If you see this page, the nginx web server is successfully installed and
  working. Further configuration is required.</p>
  
  <p>For online documentation and support please refer to
  <a href="http://nginx.org/">nginx.org</a>.<br/>
  Commercial support is available at
  <a href="http://nginx.com/">nginx.com</a>.</p>
  
  <p><em>Thank you for using nginx.</em></p>
  </body>
  </html>
  
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  root@nginx-744f4df6df-rxhph:/# curl http://nginx-service2.pwk3spi-vraptor:85
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  After googling the issue (and please correct me if I'm wrong) it seems like a coredns issue, because looking at the logs and see the error timeouts:

  $ kubectl get pods -n kube-system
  NAME                                     READY   STATUS      RESTARTS   AGE
  helm-install-traefik-qr2bd               0/1     Completed   0          153d
  metrics-server-7566d596c8-nnzg2          1/1     Running     59         148d
  svclb-traefik-kjbbr                      2/2     Running     60         153d
  traefik-758cd5fc85-wzjrn                 1/1     Running     20         62d
  local-path-provisioner-6d59f47c7-4hvf2   1/1     Running     72         148d
  coredns-7944c66d8d-gkdp4                 1/1     Running     0          3m47s
  
  $ kubectl logs coredns-7944c66d8d-gkdp4 -n kube-system
  .:53
  [INFO] plugin/reload: Running configuration MD5 = 1c648f07b77ab1530deca4234afe0d03
  CoreDNS-1.6.9
  linux/arm, go1.14.1, 1766568
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:50482->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:34160->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:53485->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:46642->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:55329->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:44471->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:49182->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:54082->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:48151->192.168.8.109:53: i/o timeout
  [ERROR] plugin/errors: 2 1898797220.1916943194. HINFO: read udp 10.42.0.38:48599->192.168.8.109:53: i/o timeout
  

  where people recommended

  • changing the coredns config map to forward to your master node IP

  ... other CoreFile stuff

  forward . host server IP

  ... other CoreFile stuff

  • or adding your coredns clusterip IP as a nameserver to /etc/resolve.conf

  search default.svc.cluster.local svc.cluster.local cluster.local

  nameserver 10.42.0.38

  nameserver 192.168.8.1

  nameserver fe80::266:19ff:fea7:85e7%wlan0

  , however didn't find that these solutions worked.

  Details for reference:

  $ kubectl get nodes -o wide
  NAME          STATUS   ROLES    AGE    VERSION        INTERNAL-IP     EXTERNAL-IP   OS-IMAGE                         KERNEL-VERSION   CONTAINER-RUNTIME
  raspberrypi   Ready    master   153d   v1.18.9+k3s1   192.168.8.109   <none>        Raspbian GNU/Linux 10 (buster)   5.10.9-v7l+      containerd://1.3.3-k3s2
  
  $ kubectl get svc -n kube-system -o wide
  NAME                 TYPE           CLUSTER-IP      EXTERNAL-IP     PORT(S)                      AGE    SELECTOR
  kube-dns             ClusterIP      10.43.0.10      <none>          53/UDP,53/TCP,9153/TCP       153d   k8s-app=kube-dns
  metrics-server       ClusterIP      10.43.205.8     <none>          443/TCP                      153d   k8s-app=metrics-server
  traefik-prometheus   ClusterIP      10.43.222.138   <none>          9100/TCP                     153d   app=traefik,release=traefik
  traefik              LoadBalancer   10.43.249.133   192.168.8.109   80:31222/TCP,443:32509/TCP   153d   app=traefik,release=traefik
  
  $ kubectl get ep kube-dns -n kube-system
  NAME       ENDPOINTS                                     AGE
  kube-dns   10.42.0.38:53,10.42.0.38:9153,10.42.0.38:53   153d
  

  No idea where I'm going wrong, or if I focused on the wrong stuff, or how to continue. Any help will be much appreciated, please.
• Is there any way to bind K3s / flannel to another interface?

  I have a K3s (v1.20.4+k3s1) cluster with 3 nodes, each with two interfaces. The default interface has a public IP, the second one a 10.190.1.0 address. I installed K3s with and without the -flannel-backend=none option and then deployed flannel via " kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml", previously binding the kube-flannel container to the internal interface via the args "--iface=". In this setup the kube-flannel pods get the node-ip of the internal interface, but I can't reach the pods on the other nodes via ICPM. If I deploy flannel without -iface arg, the kube-flannel pods get an address from the 10.42.0.0 network. Then I can reach the pods of the other hosts, but the traffic will be routed through the public interfaces, which I want to avoid. Does anyone have a tip for me?