I am trying to add a side car container to an existing pod (webapp-1) to save the logs. However, I am getting error after creating the pod. The pod is crashing and the status changes to error..

For the below question i have added the yaml file. Please let me know if this is fine.

 Add a side car container to the running pod logging-pod with the blow specification

 The image of the sidecar container is busybox and the container writes the logs as below

tail -n 1 /var/log/k8slog/application.log

 The container shares the volume logs with the application container the mounts to the

directory /var/log/k8slog

 Do not alter the application container and verify the logs are written properly to the file

here is the yaml file.. I dont understand where I am making a mistake here.

apiVersion: v1

kind: Pod

metadata:

  creationTimestamp: "2021-10-25T07:54:07Z"

  labels:

    name: webapp-1

  name: webapp-1

  namespace: default

  resourceVersion: "3241"

  uid: 8cc29748-7879-4726-ac60-497ee41f7bd6

spec:

  containers:

  - image: kodekloud/event-simulator

    imagePullPolicy: Always

    name: simple-webapp

    - /bin/sh

    - -c

    - >

      i=0;

      while true;

      do

        echo "$i: $(date)" >> /var/log/k8slog/application.log

        echo "$(date) INFO $i" >>;

        i=$((i 1));

       sleep 1;

      done

    volumeMounts:

    - name: varlog

      mountPath: /var/log

  - name: count-log-1

    image: busybox

    args: [/bin/sh, -c, 'tail -n 1 /var/log/k8slog/application.log']

    volumeMounts:

    - name: varlog

      mountPath: /var/log

    ports:

    - containerPort: 8080

      protocol: TCP

    resources: {}

    terminationMessagePath: /dev/termination-log

    terminationMessagePolicy: File

    volumeMounts:

    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount

      name: default-token-fgstk

      readOnly: true

  dnsPolicy: ClusterFirst

  enableServiceLinks: true

  nodeName: controlplane

  preemptionPolicy: PreemptLowerPriority

  priority: 0

  restartPolicy: Always

  schedulerName: default-scheduler

  securityContext: {}

  serviceAccount: default

  serviceAccountName: default

  terminationGracePeriodSeconds: 30

  tolerations:

  - effect: NoExecute

    key: node.kubernetes.io/not-ready

    operator: Exists

    tolerationSeconds: 300

  - effect: NoExecute

    key: node.kubernetes.io/unreachable

    operator: Exists

    tolerationSeconds: 300

  volumes:

  - name: varlog

    mountPath: /var/log

  - name: default-token-fgstk

    secret:

      defaultMode: 420

      secretName: default-token-fgstk

status:

  conditions:

  - lastProbeTime: null

    lastTransitionTime: "2021-10-25T07:54:07Z"

    status: "True"

    type: Initialized

  - lastProbeTime: null

CodePudding user response：

First of all, You could create a directory and the logfile itself. If the count-log-1 container spin up first, it will have nothing to read and exit with an error. To to it, a good practise is to use an Init Container. https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

Second, containers need to have a shared volume, on which the logfile will be present. If there is no need to persist data, an emptyDir volume will enough. https://kubernetes.io/docs/concepts/workloads/pods/init-containers/

Finally, You hade some errors in shell commands. Full .yaml file:

apiVersion: v1
kind: Pod
metadata:
  labels:
    name: webapp-1
  name: webapp-1
  namespace: default

spec:
# Init container fo creating the log directory and file
# on the emptyDir volume, which will be passed to the containers
  initContainers:
  - name: create-log-file
    image: busybox
    command:
      - sh 
      - -c
      - |
          #!/bin/sh
          mkdir -p /var/log/k8slog
          touch /var/log/k8slog/application.log
# Mount varlog volume to the Init container
    volumeMounts:
    - name: varlog
      mountPath: /var/log

  containers:
  - image: kodekloud/event-simulator
    imagePullPolicy: Always
    name: simple-webapp
    command:
      - sh
      - -c
      - |
          i=0
          while true; do
            echo "$i: $(date)" >> /var/log/k8slog/application.log
            echo "$(date) INFO $i"
            i=$((i 1))
          sleep 1
          done
# Mount varlog volume to simple-webapp container
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  - name: count-log-1
    image: busybox
    command:
      - sh
      - -c
      - |
          tail -f -n 1 /var/log/k8slog/application.log
# Mount varlog volume to count-log-1 container
    volumeMounts:
    - name: varlog
      mountPath: /var/log

# Define na emptyDir shared volume
  volumes:
  - name: varlog
    emptyDir: {}