Kubernetes Musings

Pod Affinity

To prevent the control plane nodes from being loaded by user deployments, you can configure a Deployment or StatefulSet so that it will not place pods on control plane nodes.

The following is placed under spec.template.spec section:

 affinity:
   nodeAffinity:
     requiredDuringSchedulingIgnoredDuringExecution:
       nodeSelectorTerms:
       - matchExpressions:
         - key: node-role.kubernetes.io/control-plane
           operator: DoesNotExist

Do this for your app and database pods, and then apply the YAML file to stop and restart the pod(s).

 

Determining pod location

To see where a pod is running, use:

kubectl get pods {-A | -n NAMESPACE} -o wide

 

To see what pods are running on a node, use:

kubectl get pods -A -o wide --field-selector spec.nodeName=NODE-NAME

Temperature (Raspberry PI)

To find out the temperature, and see if there is/was throttling, you can run these commands on a Raspberry PI 4B:

vcgencmd measure_temp
vcgencmd get_throttled

The temperature is in Celsius, and the throttling is a bit map. Some definitions I found, are:

Value    Meaning relevant here
0x0      No current/historical throttling flags
0xe0000  Historical thermal/throttling-related flags, but no current under-voltage bit
0xe0008  Same historical flags plus current under-voltage