StatefulSet

• additional points:
• pod come up sequentially / ordered by default.
  • spec > podManagemnetPolicy : OrderedReady (default)
  • change to Parallel, if needed.
• no random pod name, each pod has ordinal-index at end.
• first pod is always MASTER
• same like Deployment. Replace Deployment with StatefulSet.

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headless service ( optional )

• scenario: mysql-pod-0 MASTER (R/W), mysql-pod-1 (R), mysql-pod-2 (R) - write happen only from MASTER.
• create regular service with ClusterIP: None + ( selector and ports ). eg: mysql-h
• headless service, creates DNS a-record to access pod directly only if:
• add subdomain and hostname for pod are present., adding manually bad. All ns will be same.
• rather add serviceName in StatefulSet, it automatically assigns subdomain(mysql-h) and hostname(mysql-index) for pod/s (better).
• 
• 
• dns
• headless-service (No ClusterIP): pod-1.service-1.namespace-1.svc.cluster.local

• service (clusterIP): service-1.namespace-1.svc.cluster.local

• example : mysql-pod (DB replica)

• 

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volume

all pod needs common

• 

separate volume for each pod.

• add volumeClaimTemplate in statefulSet. (outside spec)
• inside section is PVC only.
• if pod goes down, new pod will be attached to same PVC. thus stable storage.
•