Kubernetes：如何調試 CrashLoopBackOff

Question

我有以下設置：

omg/telperion hub 上的 docker image omg/telperion一個 kubernetes 集群（有 4 個節點，每個節點有~50GB RAM）和大量資源

我按照教程將圖像從 dockerhub 拉到 kubernetes

SERVICE_NAME=telperion
DOCKER_SERVER="https://index.docker.io/v1/"
DOCKER_USERNAME=username
DOCKER_PASSWORD=password
DOCKER_EMAIL="omg@whatever.com"

# Create secret
kubectl create secret docker-registry dockerhub --docker-server=$DOCKER_SERVER --docker-username=$DOCKER_USERNAME --docker-password=$DOCKER_PASSWORD --docker-email=$DOCKER_EMAIL

# Create service yaml
echo "apiVersion: v1 \n\
kind: Pod \n\
metadata: \n\
  name: ${SERVICE_NAME} \n\
spec: \n\
  containers: \n\
    - name: ${SERVICE_NAME} \n\
      image: omg/${SERVICE_NAME} \n\
      imagePullPolicy: Always \n\
      command: [ \"echo\",\"done deploying $SERVICE_NAME\" ] \n\
  imagePullSecrets: \n\
    - name: dockerhub" > $SERVICE_NAME.yaml

 # Deploy to kubernetes
 kubectl create -f $SERVICE_NAME.yaml

這導致 pod 進入CrashLoopBackoff

docker run -it -p8080:9546 omg/telperion工作正常。

所以我的問題是這是否可以調試？如果是這樣，我該如何調試？

一些日志：

kubectl get nodes                                                                                          
NAME                    STATUS                     AGE       VERSION
k8s-agent-adb12ed9-0    Ready                      22h       v1.6.6
k8s-agent-adb12ed9-1    Ready                      22h       v1.6.6
k8s-agent-adb12ed9-2    Ready                      22h       v1.6.6
k8s-master-adb12ed9-0   Ready,SchedulingDisabled   22h       v1.6.6

.

kubectl get pods                                                                                               
NAME                        READY     STATUS             RESTARTS   AGE
telperion                    0/1       CrashLoopBackOff   10         28m

.

kubectl describe pod telperion
Name:           telperion
Namespace:      default
Node:           k8s-agent-adb12ed9-2/10.240.0.4
Start Time:     Wed, 21 Jun 2017 10:18:23 +0000
Labels:         <none>
Annotations:    <none>
Status:         Running
IP:             10.244.1.4
Controllers:    <none>
Containers:
  telperion:
    Container ID:       docker://c2dd021b3d619d1d4e2afafd7a71070e1e43132563fdc370e75008c0b876d567
    Image:              omg/telperion
    Image ID:           docker-pullable://omg/telperion@sha256:c7e3beb0457b33cd2043c62ea7b11ae44a5629a5279a88c086ff4853828a6d96
    Port:
    Command:
      echo
      done deploying telperion
    State:              Waiting
      Reason:           CrashLoopBackOff
    Last State:         Terminated
      Reason:           Completed
      Exit Code:        0
      Started:          Wed, 21 Jun 2017 10:19:25 +0000
      Finished:         Wed, 21 Jun 2017 10:19:25 +0000
    Ready:              False
    Restart Count:      3
    Environment:        <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-n7ll0 (ro)
Conditions:
  Type          Status
  Initialized   True
  Ready         False
  PodScheduled  True
Volumes:
  default-token-n7ll0:
    Type:       Secret (a volume populated by a Secret)
    SecretName: default-token-n7ll0
    Optional:   false
QoS Class:      BestEffort
Node-Selectors: <none>
Tolerations:    <none>
Events:
  FirstSeen     LastSeen        Count   From                            SubObjectPath                                   Type            Reason          Message
  ---------     --------        -----   ----                            -------------                                   --------        ------          -------
  1m            1m              1       default-scheduler                                                               Normal          Scheduled       Successfully assigned telperion to k8s-agent-adb12ed9-2
  1m            1m              1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal          Created         Created container with id d9aa21fd16b682698235e49adf80366f90d02628e7ed5d40a6e046aaaf7bf774
  1m            1m              1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal          Started         Started container with id d9aa21fd16b682698235e49adf80366f90d02628e7ed5d40a6e046aaaf7bf774
  1m            1m              1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal          Started         Started container with id c6c8f61016b06d0488e16bbac0c9285fed744b933112fd5d116e3e41c86db919
  1m            1m              1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal          Created         Created container with id c6c8f61016b06d0488e16bbac0c9285fed744b933112fd5d116e3e41c86db919
  1m            1m              2       kubelet, k8s-agent-adb12ed9-2                                                   Warning         FailedSync      Error syncing pod, skipping: failed to "StartContainer" for "telperion" with CrashLoopBackOff: "Back-off 10s restarting failed container=telperion pod=telperion_default(f4e36a12-566a-11e7-99a6-000d3aa32f49)"

  1m    1m      1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal  Started         Started container with id 3b911f1273518b380bfcbc71c9b7b770826c0ce884ac876fdb208e7c952a4631
  1m    1m      1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal  Created         Created container with id 3b911f1273518b380bfcbc71c9b7b770826c0ce884ac876fdb208e7c952a4631
  1m    1m      2       kubelet, k8s-agent-adb12ed9-2                                                   Warning FailedSync      Error syncing pod, skipping: failed to "StartContainer" for "telperion" with CrashLoopBackOff: "Back-off 20s restarting failed container=telperion pod=telperion_default(f4e36a12-566a-11e7-99a6-000d3aa32f49)"

  1m    50s     4       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal  Pulling         pulling image "omg/telperion"
  47s   47s     1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal  Started         Started container with id c2dd021b3d619d1d4e2afafd7a71070e1e43132563fdc370e75008c0b876d567
  1m    47s     4       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal  Pulled          Successfully pulled image "omg/telperion"
  47s   47s     1       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Normal  Created         Created container with id c2dd021b3d619d1d4e2afafd7a71070e1e43132563fdc370e75008c0b876d567
  1m    9s      8       kubelet, k8s-agent-adb12ed9-2   spec.containers{telperion}      Warning BackOff         Back-off restarting failed container
  46s   9s      4       kubelet, k8s-agent-adb12ed9-2                                                   Warning FailedSync      Error syncing pod, skipping: failed to "StartContainer" for "telperion" with CrashLoopBackOff: "Back-off 40s restarting failed container=telperion pod=telperion_default(f4e36a12-566a-11e7-99a6-000d3aa32f49)"

編輯 1：kubelet 在 master 上報告的錯誤：

journalctl -u kubelet

.

Jun 21 10:28:49 k8s-master-ADB12ED9-0 docker[1622]: E0621 10:28:49.798140    1809 fsHandler.go:121] failed to collect filesystem stats - rootDiskErr: du command failed on /var/lib/docker/overlay/5cfff16d670f2df6520360595d7858fb5d16607b6999a88e5dcbc09e1e7ab9ce with output
Jun 21 10:28:49 k8s-master-ADB12ED9-0 docker[1622]: , stderr: du: cannot access '/var/lib/docker/overlay/5cfff16d670f2df6520360595d7858fb5d16607b6999a88e5dcbc09e1e7ab9ce/merged/proc/13122/task/13122/fd/4': No such file or directory
Jun 21 10:28:49 k8s-master-ADB12ED9-0 docker[1622]: du: cannot access '/var/lib/docker/overlay/5cfff16d670f2df6520360595d7858fb5d16607b6999a88e5dcbc09e1e7ab9ce/merged/proc/13122/task/13122/fdinfo/4': No such file or directory
Jun 21 10:28:49 k8s-master-ADB12ED9-0 docker[1622]: du: cannot access '/var/lib/docker/overlay/5cfff16d670f2df6520360595d7858fb5d16607b6999a88e5dcbc09e1e7ab9ce/merged/proc/13122/fd/3': No such file or directory
Jun 21 10:28:49 k8s-master-ADB12ED9-0 docker[1622]: du: cannot access '/var/lib/docker/overlay/5cfff16d670f2df6520360595d7858fb5d16607b6999a88e5dcbc09e1e7ab9ce/merged/proc/13122/fdinfo/3': No such file or directory
Jun 21 10:28:49 k8s-master-ADB12ED9-0 docker[1622]:  - exit status 1, rootInodeErr: <nil>, extraDiskErr: <nil>

編輯 2：更多日志

kubectl logs $SERVICE_NAME -p                                                                                                    
done deploying telperion

Answer 1

您可以使用以下命令訪問 Pod 的日志

kubectl logs [podname] -p

-p 選項將讀取前一個（崩潰）實例的日志

如果崩潰來自應用程序，您應該在那里有有用的日志。

Answer 2

CrashLoopBackOff告訴 Pod 在啟動后立即崩潰。 Kubernetes 嘗試再次啟動 pod，但 pod 再次崩潰，這進入了循環。

您可以通過kubectl logs <pod-name> -n <namespace> --previous檢查 pod 日志是否有任何錯誤

--previous 將向您顯示容器先前實例化的日志

接下來，您可以通過描述 pod kubectl describe pod -n 來查看“狀態原因”、“最后狀態原因”和“事件”部分

“狀態原因”，“最后狀態原因”

有時問題可能是因為提供給應用程序的內存或 CPU 較少。

Answer 3

我寫了一個開源工具來做到這一點（ robusta.dev ）。 這是 Slack 中的示例輸出（它也可以發送到其他目的地）：

或多或少我正在做以下事情：

1. 獲取容器狀態和其他有用信息（重啟計數等）
2. 獲取前一個容器運行的日志（它只是崩潰了，所以我們想要以前的日志，而不是當前的日志）

我稍微簡化了代碼，但這里是實現上述內容的 Python 代碼：

@action
def restart_loop_reporter(event: PodEvent, config: RestartLoopParams):
    """
    When a pod is in restart loop, debug the issue, fetch the logs, and send useful information on the restart
    """
    pod = event.get_pod()
    crashed_container_statuses = get_crashing_containers(pod.status, config)

    # this callback runs on every pod update, so filter out ones without crashing pods
    if len(crashed_container_statuses) == 0:
        return  # no matched containers

    pod_name = pod.metadata.name

    # don't run this too frequently for the same crashing pod
    if not RateLimiter.mark_and_test(
        "restart_loop_reporter", pod_name + pod.metadata.namespace, config.rate_limit
    ):
        return

    # thi is the data we send to Slack / other destinations
    blocks: List[BaseBlock] = []
    for container_status in crashed_container_statuses:
        blocks.append(
            MarkdownBlock(
                f"*{container_status.name}* restart count: {container_status.restartCount}"
            )
        )
        
        ...
    
        container_log = pod.get_logs(container_status.name, previous=True)
        if container_log:
            blocks.append(FileBlock(f"{pod_name}.txt", container_log))
        else:
            blocks.append(
                MarkdownBlock(
                    f"Container logs unavailable for container: {container_status.name}"
                )
            )

    event.add_enrichment(blocks)

你可以在 Github 上看到實際的代碼。 沒有我的簡化。