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I use Kubernetes for work. We utilize GKE in google cloud. There have been a few times things have required some editing of our YAML files, such as when we ha

I use Kubernetes for work. We utilize GKE in google cloud. There have been a few times things have required some editing of our YAML files, such as when we had to change the first line of our yaml from: apiVersion: apps/Betav1 kind: Deployment to: apiVersion: apps/v1 kind: Deployment Because in K8s 1.16, they stopped the backwards compatibility for Beta on deployments. But that was quite some time they left it in for backwards compatibility, and it was a simple sed script to change it. We have never changed our Dockerfiles except to change the FROM line when we update a base image. They often introduce new features, but try to keep things as stable as possible for existing setups. In our case, we store our YAML in git, and can deploy a new cluster with all our microservices in about 10 min (most of that is delays in the google global load-balancer setting up a TLS certificate for us, the machines are up and running after just a few minutes). There can be a bit more scripting needed to do updates of the nodes to newer builds with no downtime, if your pods aren't totally stateless, but compared to what it used to be at an old job, with C apps running on Linux, behind load-balancers that had to be removed, upgraded, and added, a rolling update is like black magic.

Speranskiy 6y ago
> and can deploy a new cluster with all our microservices in about 10 min I know nothing about k8s yet, but try to solve the same issue with docker swarm and one thing I'm unable to get my head around is this: as soon as yaml files are stored in apps' repos and deploy is being initiated by commiting to them, how do you let the repos know about the new deployment? Or is there a tool that is present in k8s but is missing in Docker Swarm that knows about scattered yaml files' locations (git repos) and pulls them on the new deployment?
necovek 6y ago
> if your pods aren't totally stateless This is exactly the bit I care about: what do I do with "stateful" systems (my db storage, mail server data,...)? If I just mount those from external volumes, I lose a lot of idempotency and I now have to worry about whether I am trying to attach that volume to PG 9.3.1 or 9.3.2 or 12.0 (some are fine, others might cause data corruption). I know idempotent deploys are all the rage, but all those deployed apps are there to serve some data which is as stateful as it can be. I'd like a system where those external volumes are automatic snapshots on LVM (or ZFS/btrfs) when attached, but that introduces a whole another level of what-now if you need to go back to an older, now slightly stale data set. How does k8s solve this problem for me?
- tasuki 6y ago
  This question always gets asked. I'm hoping for an answer one day too!

Speranskiy 6y ago

> and can deploy a new cluster with all our microservices in about 10 min I know nothing about k8s yet, but try to solve the same issue with docker swarm and one thing I'm unable to get my head around is this: as soon as yaml files are stored in apps' repos and deploy is being initiated by commiting to them, how do you let the repos know about the new deployment? Or is there a tool that is present in k8s but is missing in Docker Swarm that knows about scattered yaml files' locations (git repos) and pulls them on the new deployment?

necovek 6y ago

> if your pods aren't totally stateless This is exactly the bit I care about: what do I do with "stateful" systems (my db storage, mail server data,...)? If I just mount those from external volumes, I lose a lot of idempotency and I now have to worry about whether I am trying to attach that volume to PG 9.3.1 or 9.3.2 or 12.0 (some are fine, others might cause data corruption). I know idempotent deploys are all the rage, but all those deployed apps are there to serve some data which is as stateful as it can be. I'd like a system where those external volumes are automatic snapshots on LVM (or ZFS/btrfs) when attached, but that introduces a whole another level of what-now if you need to go back to an older, now slightly stale data set. How does k8s solve this problem for me?

tasuki 6y ago
This question always gets asked. I'm hoping for an answer one day too!