Vfrdtyky

I have a container running inside a pod and I want to be able to monitor its content every week. I want to write a Kube cronjob for it. Is there a best way to do this?

At the moment I am doing this by running a script in my local machine that does kubectl exec my-container and monitors the content of the directory in that container.

kubectl exec my-container sounds perfectly fine to me. You might want to look at this if you want to run kubectl in a pod (Kubernetes CronJob).

There are other ways but depending on what you are trying to do in the long term it might be an overkill. For example:

• You can set up a Fluentd or tail/grep sidecar (or ls, if you are using a binary file?) to send the content or part of the content of that file to an Elasticsearch cluster.




• You can set up Prometheus in Kubernetes to scrape metrics on the pod mounted filesystems. You will probably have to use a custom exporter in the pod or something else that exports files in mount points in the pod. This is a similar example.

You can run your script in another sidecar of your pod.

• Define a empty directory volume


• Mount this volume as your content directory


• Also mount this directory to sidecar, so that it can access and able to monitor.

Example:

apiVersion: v1

kind: Pod

metadata:

  name: monitor-by-sidecar

spec:



  restartPolicy: Never



  volumes: # empty directory volume

  - name: shared-data

    emptyDir: {}



  containers:



  - name: container-which-produce-content # This container is main application which generate contect. Suppose in /usr/share/nginx/html directory

    image: debian

    volumeMounts:

    - name: shared-data

      mountPath: /usr/share/nginx/html

    command: ["/bin/bash", "-c"]

    args:

      - while true;

        do 

        echo "hello world";

        echo "----------------" > /usr/share/nginx/html/index.html;

        cat /usr/share/nginx/html/index.html;

        done



  - name: container-which-run-script-to-monitor # this container will run your monitor scripts. this container mount main application's volume in /pod-data directory and run required scripts.

    image: debian

    volumeMounts:

    - name: shared-data

      mountPath: /pod-data

    command: ["/bin/sh", "-c"]

    args:

    - while true; 

      do 

      echo "hello"; 

      sleep 10;

      ls -la /pod-data/;

      cat /pod-data/index.html;

      done

Example Description

• First container(named container-which-produce-content) is main application, which mount a emptyDir volume in /usr/share/nginx/html. In this directory main application will generate data.


• Second container(named container-which-run-script-to-monitor) will mount same emptyDir volume (named shared-data which also mounted by main application in /usr/share/nginx/html dir) in /pod-data directory. This /pod-data contains whole data which main application generated in /usr/share/nginx/html directory. You can then run your scripts on this directory.