docker - 程序干净退出，但 kubernetes 处于 CrashLoopBackOff 中

Question

我创建了一个连接到服务器、rpc 交换、登录和退出的 Go 客户端。在 kubernetes 中部署，我希望这会从“Running -> Completed -> Running”循环中移动，类似于 dnsutils 的方式。使用“sleep 3600”命令部署运行一个小时并退出。

我将其简化为最小的 go 程序，以确保没有复杂性侵入，这是:

k8s-tester ➜ cat client.go
package main   
func main() {
    return
}

不过，当我这样做时，我实际上看到它经历了“ Running -> Completed -> CrashLoopBackOff -> Running”状态。

问: 为什么当从 shell 运行时，kubernetes 将此程序视为崩溃，显示退出状态为 0 (EXIT_SUCCESS)？

  k8s-tester ➜ kubectl create deployment --image kvaradha/client test-client  deployment.apps/test-client created  k8s-tester ➜ kubectl get pods -w -o wide  NAME                                  READY   STATUS      RESTARTS   AGE   IP           NODE             NOMINATED NODE   READINESS GATES  hello-world-server-85486b969b-x744z   1/1     Running     0          10h   10.1.0.159   docker-desktop                linux-544887f4fb-gksd8                1/1     Running     12         14h   10.1.0.156   docker-desktop                postgres-57944b47cb-2cqtk             1/1     Running     0          13d   10.1.0.136   docker-desktop                test-client-74cddbb988-rxx8f          0/1     Completed   1          4s    10.1.0.169   docker-desktop                test-client-74cddbb988-rxx8f          0/1     CrashLoopBackOff   1          5s    10.1.0.169   docker-desktop                test-client-74cddbb988-rxx8f          0/1     Completed          2          21s   10.1.0.169   docker-desktop                test-client-74cddbb988-rxx8f          0/1     CrashLoopBackOff   2          33s   10.1.0.169   docker-desktop                test-client-74cddbb988-rxx8f          0/1     Completed          3          50s   10.1.0.169   docker-desktop                test-client-74cddbb988-rxx8f          0/1     CrashLoopBackOff   3          62s   10.1.0.169   docker-desktop              

更多细节:

我使用的简单 Dockerfile:

FROM scratch
MAINTAINER "kannan@ieee.org"
ARG  ARCH
COPY client /client
ENTRYPOINT [ "/client" ]

构建和部署为:

CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o client .
docker build -t kvaradha/client .
kubectl create deployment --image kvaradha/client test-client

@sfrehse 建议的 docker 输出:
k8s-tester ➜ docker run --rm kvaradha/client
2020/02/28 21:33:17 hostname: 127.0.0.1:65432 name: H809430
k8s-tester ➜ echo $?
0

@CurtisMatton:描述 pods 让我明白:

Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 2m2s default-scheduler Successfully assigned default/test-client-74cddbb988-jmxmd to docker-desktop
Warning Failed 110s kubelet, docker-desktop Failed to pull image "kvaradha/client": rpc error: code = Unknown desc = Error response from daemon: Get https://registry-1.docker.io/v2/: net/http: TLS handshake timeout
Warning Failed 110s kubelet, docker-desktop Error: ErrImagePull
Normal BackOff 109s kubelet, docker-desktop Back-off pulling image "kvaradha/client"
Warning Failed 109s kubelet, docker-desktop Error: ImagePullBackOff
Normal Pulling 55s (x4 over 2m1s) kubelet, docker-desktop Pulling image "kvaradha/client"
Normal Created 54s (x3 over 2m) kubelet, docker-desktop Created container client
Normal Pulled 54s (x3 over 2m) kubelet, docker-desktop Successfully pulled image "kvaradha/client"
Normal Started 53s (x3 over 2m) kubelet, docker-desktop Started container client
Warning BackOff 9s (x7 over 96s) kubelet, docker-desktop Back-off restarting failed container

用“FROM golang”构建了一个容器，最终结果相同:

test-client-bd4c475d4-cmnd6 1/1 Running 2 30s
test-client-bd4c475d4-cmnd6 0/1 Completed 2 31s
hello-world-client-77775898c-564lt 0/1 Completed 325 27h
test-client-bd4c475d4-cmnd6 0/1 CrashLoopBackOff 2 44s
hello-world-client-77775898c-564lt 0/1 CrashLoopBackOff 325 27h

Answer 1

这是预期的和预期的行为。 Kubernetes 的主要工作是确保给定的应用程序始终运行。如果应用程序退出(无论退出代码如何)，Kubernetes(更具体地说是 kubelet 守护进程)将假定应用程序已崩溃并重新启动它。因此，您的应用程序应该是一个长时间运行的进程(即:服务器)。

如果您的应用程序只运行一次然后干净地退出，Kubernetes Job会比部署更合适。这样 pod 将运行完成而没有 CrashLoopBackOff错误。