PDB (Pod Disruption Budget)¶

https://kubernetes.io/docs/tasks/run-application/configure-pdb/

A PodDisruptionBudget has three fields:

• A label selector .spec.selector to specify the set of pods to which it applies

• .spec.minAvailable which is a description of the number of pods from that set that must still be available after the eviction, even in the absence of the evicted pod. absolute number or a percentage.

• .spec.maxUnavailable which is a description of the number of pods from that set that can be unavailable after the eviction. absolute number or a percentage.

get pdb apiversion in kubernetes¶

kubectl api-resources | grep pdb

minAvailable or maxUnavailable¶

• minAvailable: the number of Pods that must be available during a disruption

• maxUnavailable: the number of Pods that may be disrupted

• only one of minAvailable and maxUnavailable in a single PodDisruptionBudget can be specified

• an integer represents the number of Pods. If minAvailable = 10, then 10 Pods must always be available, even during a disruption.

• a percentage as a string (e.g. "50%") represents a percentage of total Pods. If minAvailable = 50%", then at least 50% of the Pods (rounded) remain available during a disruption.

ALLOWED DISRUPTIONS¶

• ALLOWED DISRUPTIONS = 0 when there are not any pods matching app: my-app in the namespace ALLOWED DISRUPTIONS = 1 disruption controller has seen the pods, counted the matching pods, and updated the status of the PDB

  kubectl -n <namespace> get pdb <pdb-name>
  kubectl -n <namespace> get pdb <pdb-name> -o yaml
  

Cannot evict pod as it would violate the pod's disruption budget¶

NAMESPACE  NAME              MIN AVAILABLE  MAX UNAVAILABLE  ALLOWED DISRUPTIONS  AGE
jhub       user-placeholder  0              N/A              0                    10d
jhub       user-scheduler    N/A            1                1                    10d