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The ungleich kubernetes infrastructure » History » Version 19

Nico Schottelius, 07/25/2021 11:11 AM

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h1. The ungleich kubernetes infrastructure
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h2. Status
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This document is **pre-production**
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h2. k8s clusters
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| Cluster | Purpose | Init/Notes | flux |
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| c0.k8s.ooo | Dev | @kubeadm init --config k8s/c0/kubeadm.yaml --upload-certs@ |
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| c1.k8s.ooo | Dev p6 | VM based | @kubeadm init --config k8s/c1/kubeadm.yaml@ | | 
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| c2.k8s.ooo | Demo/Semiprod | @kubeadm init --config k8s/c2/kubeadm.yaml --upload-certs@ | @flux bootstrap git --url=ssh://git@code.ungleich.ch/ungleich-intern/k8s-config.git --path=cluster/c2 --network-policy false --cluster-domain c2.k8s.ooo@ |
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| c3.k8s.ooo | Dev p6 | VM based |
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| p5.k8s.ooo | Prod | Place5 |
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| p6.k8s.ooo | Prod | Place6 |
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| p7.k8s.ooo | Prod | Place7 |
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h2. General architecture and components overview
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* All k8s clusters are IPv6 only
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* We use BGP peering to propagate podcidr and serviceCidr networks to our infrastructure
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* The main / public repository is "ungleich-k8s":https://code.ungleich.ch/ungleich-public/ungleich-k8s
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th2. ungleich kubernetes infrastructure v1
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We are using the following components:
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* "Calico as a CNI":https://www.projectcalico.org/ with BGP, IPv6 only, no encapsulation
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** Needed for basic networking
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* "kubernetes-secret-generator":https://github.com/mittwald/kubernetes-secret-generator for creating secrets
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** Needed so that secrets are not stored in the git repository, but only in the cluster
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* "ungleich-certbot":https://hub.docker.com/repository/docker/ungleich/ungleich-certbot 
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** Needed to get letsencrypt certificates for services
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* "rook with ceph rbd + cephfs":https://rook.io/ for storage
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** rbd for almost everything, *ReadWriteOnce*
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** cephfs for smaller things, multi access *ReadWriteMany*
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** Needed for providing persistent storage
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* "flux v2":https://fluxcd.io/ 
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** Needed to manage resources automatically
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h3. Persistent storage setup 
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* 3 or 5 monitors
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h3. Cluster types
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| **Type/Feature** | **Development** | **Production** |
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| Min No. nodes | 3 (1 master, 3 worker) | 5 (3 master, 3 worker) |
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| Recommended minimum | 4 (dedicated master, 3 worker) | 8 (3 master, 5 worker) |
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| Separation of control plane | optional | recommended |
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| Persistent storage | required | required |
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| Number of storage monitors | 3 | 5 |
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h2. Operations
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h3. Installing a new k8s cluster
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* Decide on the cluster name (usually *cX.k8s.ooo*), X counting upwards
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* Use cdist to configure the nodes with requirements like crio
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* Decide between single or multi node control plane setups (see below)
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* Setup DNS delegation and glue records:
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** kube-dns.kube-system.svc.cX AAAA ...
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** kube-dns.kube-system.svc.cX A ...
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** cX NS kube-dns.kube-system.svc.cX
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h2. Open Issues / To be discussed
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* "Maybe add Autoscaling support?":https://github.com/kubernetes-sigs/metrics-server
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** https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/
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** https://github.com/kubernetes/autoscaler/tree/master/vertical-pod-autoscaler/
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* Certainly deploy in-cluster monitoring
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** "prometheus-operator":https://github.com/prometheus-operator/prometheus-operator CR
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** "kube-prometheus":https://github.com/prometheus-operator/kube-prometheus complete example, based on prometheus-operator
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** "kubernetes dashboard":https://github.com/kubernetes/dashboard generic cluster overview, basically kubectl for a broswer + graphs
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** "kube-prometheus-stack via helm":https://github.com/prometheus-community/helm-charts/tree/main/charts/kube-prometheus-stack#kube-prometheus-stack
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*** Looks most fitting, testing it in #9468
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* Matrix/Notification bot
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** Informing about changes in the cluster