对 Kubernetes API 服务器的 REST API 请求，GET , POST , PUT 等都是请求，响应，简单易懂，例如 kubectl create <something>。我想知道当我执行kubectl logs -f <pod-name>（以及类似kubectl attach <pod>之类的操作）时API服务器如何为pod日志提供服务，它只是循环中对GET的http响应吗？
【问题讨论】：
标签： kubernetes
是的，当查看logs.go 的源时，它看起来目前只是kubectl 正在使用的HTTP GET，尽管似乎需要unify and upgrade 几个命令（exec， port-forward、logs 等）到 WebSockets。
展示 Maciej 的出色建议：
$ kubectl run test --image centos:7 \
-- sh -c "while true ; do echo Work ; sleep 2 ; done"
$ kubectl get po
NAME READY STATUS RESTARTS AGE
test-769f6f8c9f-2nx7m 1/1 Running 0 2m
$ kubectl logs -v9 -f test-769f6f8c9f-2nx7m
I1019 13:49:34.282007 71247 loader.go:359] Config loaded from file /Users/mhausenblas/.kube/config
I1019 13:49:34.284698 71247 loader.go:359] Config loaded from file /Users/mhausenblas/.kube/config
I1019 13:49:34.292620 71247 loader.go:359] Config loaded from file /Users/mhausenblas/.kube/config
I1019 13:49:34.293136 71247 round_trippers.go:386] curl -k -v -XGET -H "Accept: application/json, */*" -H "User-Agent: kubectl/v1.12.0 (darwin/amd64) kubernetes/0ed3388" 'https://192.168.64.13:8443/api/v1/namespaces/default/pods/test-769f6f8c9f-2nx7m'
I1019 13:49:34.305016 71247 round_trippers.go:405] GET https://192.168.64.13:8443/api/v1/namespaces/default/pods/test-769f6f8c9f-2nx7m 200 OK in 11 milliseconds
I1019 13:49:34.305039 71247 round_trippers.go:411] Response Headers:
I1019 13:49:34.305047 71247 round_trippers.go:414] Date: Fri, 19 Oct 2018 12:49:34 GMT
I1019 13:49:34.305054 71247 round_trippers.go:414] Content-Type: application/json
I1019 13:49:34.305062 71247 round_trippers.go:414] Content-Length: 2390
I1019 13:49:34.305125 71247 request.go:942] Response Body: {"kind":"Pod","apiVersion":"v1","metadata":{"name":"test-769f6f8c9f-2nx7m","generateName":"test-769f6f8c9f-","namespace":"default","selfLink":"/api/v1/namespaces/default/pods/test-769f6f8c9f-2nx7m","uid":"0581b0fa-d39d-11e8-9827-42a64713caf8","resourceVersion":"892912","creationTimestamp":"2018-10-19T12:46:39Z","labels":{"pod-template-hash":"3259294759","run":"test"},"ownerReferences":[{"apiVersion":"apps/v1","kind":"ReplicaSet","name":"test-769f6f8c9f","uid":"057f3ad4-d39d-11e8-9827-42a64713caf8","controller":true,"blockOwnerDeletion":true}]},"spec":{"volumes":[{"name":"default-token-fbx4m","secret":{"secretName":"default-token-fbx4m","defaultMode":420}}],"containers":[{"name":"test","image":"centos:7","args":["sh","-c","while true ; do echo Work ; sleep 2 ; done"],"resources":{},"volumeMounts":[{"name":"default-token-fbx4m","readOnly":true,"mountPath":"/var/run/secrets/kubernetes.io/serviceaccount"}],"terminationMessagePath":"/dev/termination-log","terminationMessagePolicy":"File","imagePullPolicy":"IfNotPresent"}],"restartPolicy":"Always","terminationGracePeriodSeconds":30,"dnsPolicy":"ClusterFirst","serviceAccountName":"default","serviceAccount":"default","nodeName":"minikube","securityContext":{},"schedulerName":"default-scheduler","tolerations":[{"key":"node.kubernetes.io/not-ready","operator":"Exists","effect":"NoExecute","tolerationSeconds":300},{"key":"node.kubernetes.io/unreachable","operator":"Exists","effect":"NoExecute","tolerationSeconds":300}]},"status":{"phase":"Running","conditions":[{"type":"Initialized","status":"True","lastProbeTime":null,"lastTransitionTime":"2018-10-19T12:46:39Z"},{"type":"Ready","status":"True","lastProbeTime":null,"lastTransitionTime":"2018-10-19T12:46:40Z"},{"type":"ContainersReady","status":"True","lastProbeTime":null,"lastTransitionTime":null},{"type":"PodScheduled","status":"True","lastProbeTime":null,"lastTransitionTime":"2018-10-19T12:46:39Z"}],"hostIP":"192.168.64.13","podIP":"172.17.0.11","startTime":"2018-10-19T12:46:39Z","containerStatuses":[{"name":"test","state":{"running":{"startedAt":"2018-10-19T12:46:39Z"}},"lastState":{},"ready":true,"restartCount":0,"image":"centos:7","imageID":"docker-pullable://centos@sha256:67dad89757a55bfdfabec8abd0e22f8c7c12a1856514726470228063ed86593b","containerID":"docker://5c25f5fce576d68d743afc9b46a9ea66f3cd245f5075aa95def623b6c2d93256"}],"qosClass":"BestEffort"}}
I1019 13:49:34.316531 71247 loader.go:359] Config loaded from file /Users/mhausenblas/.kube/config
I1019 13:49:34.317000 71247 round_trippers.go:386] curl -k -v -XGET -H "Accept: application/json, */*" -H "User-Agent: kubectl/v1.12.0 (darwin/amd64) kubernetes/0ed3388" 'https://192.168.64.13:8443/api/v1/namespaces/default/pods/test-769f6f8c9f-2nx7m/log?follow=true'
I1019 13:49:34.339341 71247 round_trippers.go:405] GET https://192.168.64.13:8443/api/v1/namespaces/default/pods/test-769f6f8c9f-2nx7m/log?follow=true 200 OK in 22 milliseconds
I1019 13:49:34.339380 71247 round_trippers.go:411] Response Headers:
I1019 13:49:34.339390 71247 round_trippers.go:414] Content-Type: text/plain
I1019 13:49:34.339407 71247 round_trippers.go:414] Date: Fri, 19 Oct 2018 12:49:34 GMT
Work
Work
Work
^C
【讨论】：
我的建议是始终检查 kubectl 在掩护下做了什么，为此在您的命令中使用 -v=9。它将为您提供客户端和服务器之间的完整请求和响应。
【讨论】：
如果您在最高调试级别-v 9 上使用kubectl 和流选项-f 提取任何Kubernetes 对象，例如kubectl logs -f <pod-name> -v 9，您可以意识到kubectl 通过follow=true通过相应地从目标 Pod 获取日志来标记 API 请求，并流式传输到输出：
curl -k -v -XGET -H "接受：应用程序/json，/" -H "用户代理： kubectl/v1.12.1 (linux/amd64) kubernetes/4ed3216" 'https://API_server_IP/api/v1/namespaces/default/pods/Pod-name/log?follow=true'
您可以考虑按照以下步骤发起自己的 API 请求：
获取令牌以进行授权：
MY_TOKEN="$(kubectl get secret <default-secret> -o jsonpath='{$.data.token}' | base64 -d)"
然后您可以直接从 API 服务器手动检索所需的数据：
curl -k -v -H "Authorization : Bearer $MY_TOKEN" https://API_server_IP/api/v1/namespaces/default/pods
【讨论】：