Counter as a service (simple Apache Cassandra demo).
Usage:
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Install Cassandra Service and StatefulSet.
kubectl apply -f https://raw.githubusercontent.com/jsafrane/caas/master/cassandra.yamlChanges from Kubernetes docs:
- Reshuffled the YAML to have it in "talk friendly" order.
- No StorageClass is created. Upstream example targets minikube, we run on GCE with a default storage class.
- Lower CPU requests. We want to run the demo on a 3 node cluster and we don't require extra speed.
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Wait for Cassandra pods to be up (~6 minutes !)
- While it is starting, we can 'debug' it a bit:
$ kubectl get pvc $ kubectl describe pvc $ kubectl get pod $ kubectl describe pod cassandra-0 $ kubectl logs cassandra-0 -
Install the application.
kubectl apply -f https://raw.githubusercontent.com/jsafrane/caas/master/caas.yaml -
Test the application.
$ kubectl get service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE caas LoadBalancer 10.43.247.108 35.238.128.239 80:31501/TCP 1m $ curl http://35.238.128.239/first/html <html> <head><title>first</title></head> <body> <h1>Counter: first, value: 6</h1> ...http://35.238.128.239/<counter name>/htmlFor debugging, you can check Cassandra node status:
$ kubectl exec cassandra-0 nodetool status Datacenter: DC1-K8Demo ====================== Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- Address Load Tokens Owns (effective) Host ID Rack UN 10.40.0.8 136.15 KiB 32 100.0% d55b2a33-34a7-4216-8a21-77606832d847 Rack1-K8Demo UN 10.40.2.8 115.63 KiB 32 100.0% 7ead59de-b0ed-4b7f-b1c0-52c0344ace51 Rack1-K8Demo UN 10.40.1.5 113.59 KiB 32 100.0% 0514d1a3-e0e8-4f42-8e3e-697cf958b8d6 Rack1-K8Demo -
Scale up.
$ kubectl scale --replicas=4 statefulset/cassandra $ kubectl get pod- Database rows were redistributed to the new node:
$ kubectl exec cassandra-0 nodetool status
- Database rows were redistributed to the new node:
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Simulate "graceful" failure.
$ kubectl delete pod cassandra-1 $ kubectl get pod -w -
Scale down
$ kubectl scale --replicas=3 statefulset/cassandra $ kubectl exec cassandra-0 nodetool status Datacenter: DC1-K8Demo ====================== Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- Address Load Tokens Owns (effective) Host ID Rack UN 10.40.0.8 141.08 KiB 32 78.6% d55b2a33-34a7-4216-8a21-77606832d847 Rack1-K8Demo UN 10.40.2.8 120.56 KiB 32 86.7% 7ead59de-b0ed-4b7f-b1c0-52c0344ace51 Rack1-K8Demo UN 10.40.1.5 118.52 KiB 32 67.8% 0514d1a3-e0e8-4f42-8e3e-697cf958b8d6 Rack1-K8Demo DN 10.40.1.6 75.89 KiB 32 67.0% 9bfa542d-55ca-46b7-b109-aa10b477dfc0 Rack1-K8Demo $ kubectl exec cassandra-0 nodetool removenode 9bfa542d-55ca-46b7-b109-aa10b477dfc0 $ kubectl exec cassandra-0 nodetool status Datacenter: DC1-K8Demo ====================== Status=Up/Down |/ State=Normal/Leaving/Joining/Moving -- Address Load Tokens Owns (effective) Host ID Rack UN 10.40.0.8 141.08 KiB 32 100.0% d55b2a33-34a7-4216-8a21-77606832d847 Rack1-K8Demo UN 10.40.2.8 135.4 KiB 32 100.0% 7ead59de-b0ed-4b7f-b1c0-52c0344ace51 Rack1-K8Demo UN 10.40.1.5 128.51 KiB 32 100.0% 0514d1a3-e0e8-4f42-8e3e-697cf958b8d6 Rack1-K8Demo
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DNS
- Run nslookup in a pod in the cluster:
$ kubectl run --restart=Never --rm -ti --generator=run-pod/v1 nslookup --image=tutum/dnsutils nslookup cassandra.default.svc.cluster.local
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CQL
- Run CQL query in Cassandra:
$ kubectl run --restart=Never --rm -ti --generator=run-pod/v1 cqlsh --image=cassandra:latest -- cqlsh cassandra-0.cassandra.default.svc.cluster.local -k caas (wait a bit, a large image is pulled) cqlsh:caas> select * from counter; name | value --------+------- sample | 51