Day: October 11, 2020

why:

pod affinity: Attracts pods with with matching label.
readiness : checks pod health before sending any traffic
liveness : checks health of pod

kubectl get nodes --show-labels

kubectl label nodes <node-name> <label-key>=<label-value>

kubectl label nodes lp-knode-02 disk=ssd
kubectl label nodes lp-knode-02 nodename=lp-knode-02

apiVersion: apps/v1
kind: Deployment
metadata:
  name: httpd-affinity-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      app: httpd-affinity
  template:
    metadata:
      name: httpd-affinity-deployment
      labels:
        app: httpd-affinity
        env: prod
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: disk
                operator: In
                values:
                - ssd
      containers:        
      - name: httpd-node-affinity
        image: httpd
        imagePullPolicy: IfNotPresent
        resources:
          requests:
            memory: "256Mi"
            cpu: "100m"
          limits:
            memory: "256Mi"
            cpu: "100m"
        ports:
        - name: httpd-port
          containerPort: 80
        livenessProbe:
          httpGet:
            path: /index.html
            port: 80
            httpHeaders:
            - name: Custom-Header
              value: custom1
          initialDelaySeconds: 10
          periodSeconds: 10
          timeoutSeconds: 5
          failureThreshold: 3
        readinessProbe:
          exec:
            command:
            - cat
            - /usr/local/apache2/htdocs/index.html
          initialDelaySeconds: 10
          periodSeconds: 10

More :
https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/
https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/