Kubernetes 101 : Keeping a microservice application alive - the PodDisruptionBudgets resource -

Kubernetes could stop pods for different reasons, either to move them pods around or remove them from a node that is scheduled for maintenance.

To keep an application - backed by pods - running and serving clients, we need to keep enough pod replicas alive.

To achieve that, we could use the  PodDisruptionBudget object that tells kubernetes the percentage/number of pods that could be stopped for an application - while keeping the application alive -.

Below is an example of a PodDisruptionBudge object:

 

The "minAvailable" parameter tells kubernetes that at least six replicas of the pod with the label "run: nginx" should be running at all times.

Let's check our PodDisruptionBudget object using the below command - in case we have 9 = 6 - must have - + 3 - allowed to fail - pods running:

Remark:

The parameters of the PodDisruptionBudget can't be honored if a node hosting one of the pods fails while the number of available pods is at its minimum -"6" -. 

We could also use the "maxUnavailable" parameter to let kubernetes know the maximum number of pods - that match the given label - that could be stopped.

Below is an example of the PodDisruptionBudget that uses the "maxUnavailable" parameter:

The above example specifies that the application could afford losing at the most half "50%" of its running pods.

Remark:

The "minAvailable" and the "maxUnavailable" parameters could be integer numbers or a percentages. In case of the percentage the number is rounded up - 3.5 becomes 4 -.

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IkbalC

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