Kubernetes

Software stack

Kubernetes is installed on a cluster of computers. One master, many nodes. You don’t ssh into the cluster but talk to the master though HTTPS.

Kubernetes – the project

• Started at Google 2014. Actively worked on by people of Google, Microsoft, RedHat.
• 857 current contributors.
• Half of Fortune 100 companies use it.
• Comparison of commits/month with Docker Swarm:

Benefits

For big deployments:

• Optimal use of resources.
• Easy scaling.

For us:

• Comfortable container management.
• Full configuration as YAML files, most of them could live in the join² Git.
• Self-healing: Constant comparison of desired state and actual state.

Installation

1.   Install “naked” Ubuntu/Debian/RedHat. Disable swap.
2.   Prepare directories for persistent data.
3.   Install Docker & Kubernetes through package manager.
4.   Call “kubeadm init” on master, “kubeadm join …” on nodes.
5.   Install “Weave Net” (one-liner).
6.   Download the kubectl binary to your workstation.

Usage

• kubectl is the command line tool; your scripts may contact the HTTPS API directly.
• Kubernetes’ state is objects of different types, e.g. Deployment, CronJob, PersistentVolume, Secret, ConfigMap.
• One object, one YAML file. Typical size: 10–30 lines per object.
• All those YAML files are your wishlist.
• Typical workflow: You write YAML files and upload them with kubectl to the cluster. Then wait and see it being realised.

Some kubectl commands to get the idea:

kubectl create -f myapp.yaml
kubectl get deployments
kubectl logs myapp-1534841280-tj5mb
kubectl delete deployment myapp

Kubernetes & join²

• Highly tentative; there are no Kubernetes plans for join² yet.
• Jülich uses Kubernetes for their RDM projects, possibly also for JuSER.
• Existing images may stay as they are.
• Kubernetes and non-Kubernetes join² instances can coexist.
• 80% of YAML files would be the same for all instances. Different are: Some ConfigMaps, most Secrets, and all PersistentVolumes.
• Working on YAML files in the join² Git may streamline our configurations and improve collaboration and debugging.
• Vision: IT department offers managed Kubernetes. Then, we would't have to ssh anymore.

Thank you