July 20

Using kube-router with kubeadm-dind-cluster

v1.0

What is kube-router?

One of the options for networking in Kubernetes, is to use kube-router. This plugin uses the Bridge CNI plugin and go BGP to provide networking for the cluster.

Why use it?

With kube-router, it uses the IPVS (IP Virtual Server) kernel module, instead of iptables rules. This gives much better performance (hash vs serial lookups) and scales much better. Kube-router also uses goBGP, to provide full mesh connectivity using iBGP, instead of requiring static routes, when using the bridge plugin.

What is kubeadm-dind-cluster?

The kubeadm-dind-cluster tool that I’ve mentioned here before, allows you to create a Kubernetes cluster on single host (VM or bare-metal), by using Docker-in-Docker (it creates docker containers, which will be nodes where KubeAdm is invoked to bring up a cluster).

This tool is nice, because it saves you from doing all the tedious steps of setting up a cluster using KubeAdm manually. There are instructions in the kubeadm-dind-cluster repo, on how to use the tool to bring up a cluster.  The tools supports the bridge, calico, flannel, and weave CNI plugins.

Peanut Butter and Chocolate…

I have a PR out in kubernetes-sig/kubeadm-dind-cluster repo to add support for using kube-router, instead of kube-proxy. To use this, you can perform the following steps (assuming you have a kubeadm-dind-cluster repo pulled):

  1. Patch in the PR changes
    1. git fetch origin pull/159/head:pr159
    2. git log –abbrev-commit pr159 –oneline -n 1 | cut -f 1 -d” “
    3. git cherry-pick <# from log output>
  2. build/build-local.sh
  3. export DIND_IMAGE=mirantis/kubeadm-dind-cluster:local
  4. export CNI_PLUGIN=kube-router
  5. Bring up the cluster “./dind-cluster.sh up”

This will skip the normal bridge CNI plugin setup and creation of static routes, run a YAML file to configure the bridge CNI plugin and startup kube-router pods on each node (which will start up BGP), and will then remove the kube-proxy daemonset.

Once the cluster is up, you can “kubectl exec” into one of the kube-router pods to see the BGP and IPVS setup.

After the PR (159) is upstreamed, you’ll only need to set the CNI_PLUGIN to kube-router, and then bring up the cluster.

 

Limitations

Currently, this only works with IPv4. Although ipset and goBGP support IPv6, kube-router is not set up to run in IPv6 mode. There is a PR to add IPv6 support.



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Posted July 20, 2018 by pcm in category "Kubernetes