09 Aug 2022
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源码解析 kubectl port-forward 工作原理
本文的源码基于 Kubernetes v1.24.0，容器运行时使用 Containerd 1.5，从源码来分析 kubectl port-forward 的工作原理。
通过 port-forward 流程的分析，梳理出 kubectl -> api-server -> kubelet -> 容器运行时 的交互，了解 cri 的工作方式。
kubectl
简单创建个 pod：
kubectl run pipy --image flomesh/pipy:latest -n default
在执行 kubectl forward 时添加参数 -v 9 打印日志。
kubectl port-forward pipy 8080 -v 9
...
I0807 21:45:58.457986 14495 round_trippers.go:466] curl -v -XPOST -H "User-Agent: kubectl/v1.24.3 (darwin/arm64) kubernetes/aef86a9" -H "X-Stream-Protocol-Version: portforward.k8s.io" 'https://192.168.1.12:6443/api/v1/namespaces/default/pods/pipy/portforward'
I0807 21:45:58.484013 14495 round_trippers.go:553] POST https://192.168.1.12:6443/api/v1/namespaces/default/pods/pipy/portforward 101 Switching Protocols in 26 milliseconds
I0807 21:45:58.484029 14495 round_trippers.go:570] HTTP Statistics: DNSLookup 0 ms Dial 0 ms TLSHandshake 0 ms Duration 26 ms
I0807 21:45:58.484035 14495 round_trippers.go:577] Response Headers:
I0807 21:45:58.484040 14495 round_trippers.go:580] Upgrade: SPDY/3.1
I0807 21:45:58.484044 14495 round_trippers.go:580] X-Stream-Protocol-Version: portforward.k8s.io
I0807 21:45:58.484047 14495 round_trippers.go:580] Date: Sun, 07 Aug 2022 13:45:58 GMT
I0807 21:45:58.484051 14495 round_trippers.go:580] Connection: Upgrade
Forwarding from 127.0.0.1:8080 -> 8080
Forwarding from [::1]:8080 -> 8080
从日志可以看到请求的地址为 /api/v1/namespaces/default/pods/pipy/portforward，其中 portforward 为 pod 资源的子资源。
