Alice in the world of pods and higher order functions

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Who am I Big data developer at Captify Women Who Code Kyiv Data Engineering Lead Kubernetes and functional programming fan which loves a good story

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Alice is an adventurous girl and her curiosity may lead her to epic discoveries of the new worlds…

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Welcome to the world of pods and higher order functions

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Functional forest

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Pods kafka-2 kafka-1 kafka-0 psql-0 psql-1

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“And these ones?” - asked Alice. “Oh, better don’t look too long at them they are too complex for an unprepared eye. These are called monads”.

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“Why these houses look like constructor details?” - asks Alice. “This is one of our interesting features. All of our objects constitute type system and they are immutable”

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CONTROLLERS

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CONTROLLERS Controller- manager Custom controller

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kubectl API server Scheduler Controller- manager etcd

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kubectl API server Scheduler Controller- manager etcd kubelet kube-proxy container Pod Pod container

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Kubernetes objects map

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Pod Deployment Replica Set

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Pod Deployment Replica Set Pod Stateful Set Pod Daemon Set

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Volume Job Service Pod Deployment Replica Set Pod Stateful Set Pod Daemon Set

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Volume Job Service Pod Deployment Replica Set Pod Stateful Set Pod Daemon Set CRD

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IMMUTABLE ??? TYPE SYSTEM

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TYPE SYSTEM IMMUTABLE DECLARATIVE

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DECLARATIVE NATURE

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magic DB

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pods pure functions monads deployments stateful sets volumes

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basic-db-9.3.4

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IMPERATIVE

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YAML

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Controller- manager

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apiVersion: extensions/v1beta1 kind: Deployment metadata: name: magic-db labels: app: magic-db

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spec: containers: - image: basic-db:9.3.4 name: magic-db env: - name: DB_USER value: wizard - name: DB_NAME value: fairytale

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kubectl apply -f magic-db.yaml

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NAME READY STATUS AGE deployment/magic-db 1/1 Running 45s NAME DESIRED CURRENT AGE replicaset/magic-db 1 1 45s

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NAME READY STATUS AGE pod/magic-db-hg3 0/1 ContainerCreating 4s pod/magic-db-hg3 1/1 Running 45s magic-db- hg3

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VOLUME

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apiVersion: v1 kind: PersistentVolumeClaim metadata: name: magic-db-claim labels: app: magic-db

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spec: accessModes: - ReadWriteOnce resources: requests: storage: 10Gi

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volumeMounts: - name: magic-db mountPath: /var/lib/magic-db/data volumes: - name: magic-db persistentVolumeClaim: claimName: magic-db-claim

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NAME STATUS VOLUME CAPACITY AGE magic-db-claim Bound pv-24hjf3 10Gi 32s NAME CAPACITY STATUS CLAIM AGE pv-24hjf3 10Gi Bound magic-db-claim 32s

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magic-db- hg3

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SERVICE

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apiVersion: v1 kind: Service metadata: name: magic-db labels: app: magic-db

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spec: ports: - containerPort: 5432 name: magic-db

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NAME TYPE PORT(S) AGE service/magic-db ClusterIP 5432/TCP 5s magic-db- hg3

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SCALING

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spec: replicas: 3 template: metadata: labels: app: magic-db

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NAME READY STATUS AGE pod/magic-db-hg3 1/1 Running 3m pod/magic-db-j3t 1/1 Running 6s pod/magic-db-thw 1/1 Running 4s

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magic-db- hg3 magic-db- j3t magic-db- thw

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spec: replicas: 6 template: metadata: labels: app: magic-db

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NAME READY STATUS AGE pod/magic-db-hg3 1/1 Running 4m13s pod/magic-db-j3t 1/1 Running 53s pod/magic-db-thw 1/1 Running 53s pod/magic-db-yth 1/1 Running 4s pod/magic-db-m1n 1/1 Running 4s pod/magic-db-ito3 1/1 Running 4s

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magic-db -thw magic-db -j3t magic-db -hg3 magic-db -yth magic-db -m1n magic-db -ito3

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PURGE

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kubectl delete -f magic-db.yaml

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service "magic-db" deleted persistentvolumeclaim "magic-db-claim" deleted deployment “magic-db" deleted

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Custom controller

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kubectl API server Custom controller etcd kubelet kube-proxy container CR CR container Operator

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apiVersion: magic-repo/v1 kind: MagicDatabase metadata: name: magic-db-cluster namespace: default

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spec: teamID: “Alice-team”  volume: size: 4Gi numberOfInstances: 3 magic-db: version: “1"

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users: admin: - Alice databases: magic-world-db: admin

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NAME READY STATUS AGE pod/magic-db-cluster-0 1/1 Running 3m pod/magic-db-cluster-1 1/1 Running 6s pod/magic-db-cluster-2 1/1 Running 4s magic-db -cluster-2 magic-db -cluster-1 magic-db -cluster-0

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kubectl exec -it magic-db-cluster-0 /bin/bash @magic-db-cluster-0:/home/magic-db# mdb-sql -U Alice magic-db=#

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NAME READY STATUS AGE magic-db-operator 1/1 Running 2m33s magic-db-operator-ui 1/1 Running 72s

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conﬁg maps volumes services rbac

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apiVersion: extensions/v1beta1 kind: Deployment metadata: name: magic-db-operator labels: app: magic-db-operator

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spec: containers: - image: db-operator: v1.4.0 name: magic-db-operator serviceAccountName: magic-db-operator env: - name: CONFIG_MAP_NAME value: magic-db-operator