9a03e7e17d
Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>. Update IPVS README **What this PR does / why we need it**: People complained that they feel confused about how to use IPVS-based kube-proxy correctly, probably we may need to provide them a better README. **Which issue(s) this PR fixes**: xref: #56319 **Special notes for your reviewer**: **Release note**: ```release-note NONE ```
89 lines
2.9 KiB
Markdown
89 lines
2.9 KiB
Markdown
# How to use IPVS
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This document shows how to use kube-proxy ipvs mode.
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## What is IPVS
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**IPVS (IP Virtual Server)** implements transport-layer load balancing, usually called Layer 4 LAN switching, as part of
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Linux kernel.
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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
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and UDP-based services to the real servers, and make services of real servers appear as virtual services on a single IP address.
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## Run kube-proxy in ipvs mode
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Currently, local-up scripts and kubeadm support switching IPVS proxy mode via exporting environment variables or specifying flags.
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### Local UP Cluster
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Kube-proxy will run in iptables mode by default in a [local-up cluster](https://github.com/kubernetes/community/blob/master/contributors/devel/running-locally.md).
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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.
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### Cluster Created by Kubeadm
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Kube-proxy will run in iptables mode by default in a cluster deployed by [kubeadm](https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/).
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Since IPVS mode is still feature-gated, users should add the flag `--feature-gates=SupportIPVSProxyMode=true` in `kubeadm init` command
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```
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kubeadm init --feature-gates=SupportIPVSProxyMode=true
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```
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to specify the ipvs mode before deploying the cluster if want to run kube-proxy in ipvs mode.
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If you are using kubeadm with a configuration file, you can specify the ipvs mode adding `SupportIPVSProxyMode: true` below the `featureGates` field.
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Then the configuration file is similar to:
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```json
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kind: MasterConfiguration
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apiVersion: kubeadm.k8s.io/v1alpha1
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...
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featureGates:
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SupportIPVSProxyMode: true
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mode: ipvs
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```
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## Debug
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### Check IPVS proxy rules
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People can use `ipvsadm` tool to check whether kube-proxy are maintaining IPVS rules correctly. For example, we may get IPVS proxy rules like:
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```shell
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# ipvsadm -ln
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IP Virtual Server version 1.2.1 (size=4096)
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Prot LocalAddress:Port Scheduler Flags
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-> RemoteAddress:Port Forward Weight ActiveConn InActConn
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TCP 10.0.0.1:443 rr persistent 10800
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-> 10.229.43.2:6443 Masq 1 0 0
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TCP 10.0.0.10:53 rr
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UDP 10.0.0.10:53 rr
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```
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### Why kube-proxy can't start IPVS mode
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People can do the following check list step by step:
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**1. Enable IPVS feature gateway**
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Currently IPVS-based kube-proxy is still in alpha phase, people need to enable `--feature-gates=SupportIPVSProxyMode=true` explicitly.
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**2. Specify proxy-mode=ipvs**
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Tell kube-proxy that proxy-mode=ipvs, please.
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**3. Load ipvs required kernel modules**
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The following kernel modules are required by IPVS-based kube-proxy:
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```shell
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ip_vs
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ip_vs_rr
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ip_vs_wrr
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ip_vs_sh
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nf_conntrack_ipv4
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```
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IPVS-based kube-proxy will load them automatically. If it fails to load them, please check whether they are compiled into your kernel.
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