README.md

Demo 4

Agenda

• StatefulSets
• StorageClass
• RollOut
• Secrets

Setup Cassandra

# files are present in demo4 folder and we going to use namespace as demo4
$ cd kubectl create -f demo4/ -n demo4

service/cassandra created
storageclass.storage.k8s.io/fast-sc created
statefulset.apps/cassandra created

Watch how pods are being named and created

$ kubectl get pods -n demo4 | grep cassandra

cassandra-0   1/1     Running   0          17m
cassandra-1   1/1     Running   0          16m
cassandra-2   1/1     Running   0          15m

Check how secret works

# create a secret with 2 key value pairs
$ kubectl create secret generic test-secret --from-literal=username='user1' --from-literal=password='password'

secret/test-secret created
# this secret can be accessed as environment variable or volume mount. In this sts.yaml we are using it as env var.

Check how rollout works

# Upgarde Cassndra v12 to v13
$ kubectl patch statefulset cassandra -n demo4 --type='json' -p='[{"op": "replace", "path": "/spec/template/spec/containers/0/image", "value":"gcr.io/google-samples/cassandra:v13"}]'

statefulset.apps/cassandra patched
# Post this - check the pods using 'watch -n1 "kubectl get pods -n demo4 | grep cassandra"'
# It shall provide the way rollout is happening pod per pod and thus ensuring availability of service always

Reference for Topics covered in Demo 4

• StatefulSets
• Storage Classes
• Rollout
• Secrets