Karan Sharma

Ramblings on tech, cycling, and finance

01 Jan 2020

kubectl wait

For the longest time I’ve had these commands in my .gitlab-ci.yml file for a K8s CD pipeline:

    ...
    - kubectl apply -k overlays/prod
    - echo "Waiting for 15 seconds for pods to be restarted" && sleep 15
    - kubectl get po
    ...

So, basically I apply the changes to cluster using kubectl apply and wait for arbitary decided time (15 seconds) to see the pod status, hoping by that time the new deployments would have been active and old pods would be deleted. As the traditional SRE saying goes Hope is not a strategy this was clearly hacky and I knew it back then, just didn’t priortise enough to find a replacement. Recently got to know about kubectl wait and woah, this is exactly what I needed. I can wait till either the condition is true or a timeout happens, whichever is earlier. This is so much better than the previous hack.

kubectl wait --for=condition=available --timeout=60s --all deployments 

Here the condition depends on the resource you are selecting. You can see the values for Conditions using kubectl describe <resource>. For eg, for deployment and pods:

$ kc describe deployments/{deployment_name} | grep Conditions -A 5

Conditions:
  Type           Status  Reason
  ----           ------  ------
  Progressing    True    NewReplicaSetAvailable
  Available      True    MinimumReplicasAvailable
$ kc describe pods/{pod_name} | grep Conditions -A 5

Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True 
  PodScheduled      True 

So, now you’ll set the value for condition according to your choice. This will be pretty useful in CI/CD pipelines. That’s pretty much it.


Unrelated, but I thought about doing more such short posts and be consistent with more of writing. If you liked the short and precise format or have any feedback on it, do reach out to me on Twitter.

Happy New Year :)

Fin!