I have a cluster of 3 Cassandra pods running on Kubernetes. I want to do automatic backup of my data and for that I need to run nodetool snaphot command inside of each container and I need to invoke it remotely. What is the correct way to do it from architectural point of view? Do I need modify cassandra image to have ssh deamon in it or do I need to have helper containers in cassandra pods or to do this by 'kubectl exec' Kubernetes API calls? Other options?
I think k8s cronJob resource - is what you need for backing up the data via nodetool. Generally, the cronJob has jobTemplate section with spec section within. The spec section, in turn, has containers definition, almost the same as in the Deployment. You can build your own docker image with nodetool in it (or try to find somewhere on dockerhub) and run it with your own specific configuration.
More info: https://kubernetes.io/docs/tasks/job/automated-tasks-with-cron-jobs/