ceph-csi/vendor/k8s.io/kubernetes/pkg/proxy/ipvs

How to use IPVS

This document shows how to use kube-proxy ipvs mode.

What is IPVS

IPVS (IP Virtual Server) implements transport-layer load balancing, usually called Layer 4 LAN switching, as part of Linux kernel.

IPVS runs on a host and acts as a load balancer in front of a cluster of real servers. IPVS can direct requests for TCP and UDP-based services to the real servers, and make services of real servers appear as irtual services on a single IP address.

How to use

Load IPVS kernel modules

Currently the IPVS kernel module can't be loaded automatically, so first we should use the following command to load IPVS kernel modules manually.

modprobe ip_vs
modprobe ip_vs_rr
modprobe ip_vs_wrr
modprobe ip_vs_sh
modprobe nf_conntrack_ipv4

After that, use lsmod | grep ip_vs to make sure kernel modules are loaded.

Run kube-proxy in ipvs mode

Local UP Cluster

Kube-proxy will run in iptables mode by default in a local-up cluster.

Users should export the env KUBEPROXY_MODE=ipvs to specify the ipvs mode before deploying the cluster if want to run kube-proxy in ipvs mode.

Cluster Created by Kubeadm

Kube-proxy will run in iptables mode by default in a cluster deployed by kubeadm.

Since IPVS mode is still feature-gated, users should add the flag --feature-gates=SupportIPVSProxyMode=true in kubeadm init command

kubeadm init --feature-gates=SupportIPVSProxyMode=true

to specify the ipvs mode before deploying the cluster if want to run kube-proxy in ipvs mode.

If you are using kubeadm with a configuration file, you can specify the ipvs mode adding SupportIPVSProxyMode: true below the featureGates field. Then the configuration file is similar to:

kind: MasterConfiguration
apiVersion: kubeadm.k8s.io/v1alpha1
...
featureGates:
  SupportIPVSProxyMode: true
...

Test

Use ipvsadm tool to test whether the kube-proxy start succeed. By default we may get result like:

# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  10.0.0.1:443 rr persistent 10800
  -> 10.229.43.2:6443             Masq    1      0          0         
TCP  10.0.0.10:53 rr      
UDP  10.0.0.10:53 rr