• Kubernetes livenessProbe: testing container's health

  2 min read

  
  

  Every application will, eventually, fail. In order to detect that the container is failing and being able to recover this situation by restarting it we can use the livenessProbe.

  23/08/2021

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• Fine tunning Pod scheduling using taints, tolerations and nodeSelector

  4 min read

  
  

  If we want just a subset of Pods to be able to be scheduled on a given node we can achieve it using taints and tolerations

  With a taint we can tell the cluster not to schedule Pods on this node, but with a toleration on a Pod we can allow it to tolerate this taint

  20/08/2021

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• How to avoid pods of the same Deployment to be scheduled on the same node

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  For some applications we might want to avoid having two or more Pods belonging to the same Deployment to be scheduled on different nodes, yet we don't need them to be a DaemonSet. Let's use as an example the cluster autoscaler: We would like to have two replicas but not on the same node, since if we are draining the node an there's not enough capacity on the other nodes with both Pods offline a manual intervention would be required to spawn a new node

  $ kubectl get pods -n autoscaler -o wide
  NAME                                                 READY   STATUS    RESTARTS   AGE     IP              NODE                                           NOMINATED NODE   READINESS GATES
  autoscaler-aws-cluster-autoscaler-585cc546dd-jc46d   1/1     Running   0          16h     10.103.195.47   ip-10-12-16-10.eu-west-1.compute.internal    <none>           <none>
  autoscaler-aws-cluster-autoscaler-585cc546dd-s4j2r   1/1     Running   0          16h     10.103.195.147  ip-10-12-16-10.eu-west-1.compute.internal    <none>           <none>
  

  To do so we will have to configure affinity

  11/08/2021

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• Kubernetes startupProbe: testing containers for application startup

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  Starting from Kubernetes v1.20 we can configure a startup Probe: It will check for containers to be come into service, disabling liveness and readiness checks until it succeeds.

  05/08/2021

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• Kubernetes: What's a PodDisruptionBudget?

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  In Kubernetes we can configure a PodDisruptionBudgets (PDB) to tell the cluster for a given set of Pods how they can tolerate interruptions (such as application upgrades) maintaining it's general availability.

  This Kubernetes object has graduated to GA in Kubernetes v1.21

  03/08/2021

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