Node & Cluster Troubleshooting

Node NotReady

Diagnostics:

kubectl get nodes -o wide
kubectl describe node <node-name>
# Look for: Conditions, Taints, Events, resource usage, kubelet status

Condition decision tree:

\*Only after explicit user request for remediation and confirmation of workload impact.

AKS-specific - SSH to a node:

⚠️ Warning: kubectl debug node/... creates a privileged debug pod on the node and is not a read-only diagnostic step. Default to read-only evidence gathering first. Only suggest or run this after the user explicitly asks for remediation or approves a privileged diagnostic action and understands the change-control impact.

# Create a privileged debug pod on the node
kubectl debug node/<node-name> -it --image=mcr.microsoft.com/cbl-mariner/base/core:2.0

# Check kubelet status inside the node
chroot /host systemctl status kubelet
chroot /host journalctl -u kubelet -n 50

Optional remediation if kubelet can't recover (after confirmation): cordon -> drain -> delete. AKS auto-replaces via node pool VMSS.

⚠️ Warning: These commands are disruptive. By default, stay in read-only diagnostic mode. Only suggest or run them if the user has explicitly requested remediation and confirmed they understand the workload and PodDisruptionBudget impact.

kubectl cordon <node-name>
kubectl drain <node-name> --ignore-daemonsets --delete-emptydir-data
kubectl delete node <node-name>

Node Pool Not Scaling

Cluster Autoscaler Not Triggering

Diagnostics:

# Autoscaler logs
kubectl logs -n kube-system -l app=cluster-autoscaler --tail=100

# Autoscaler status
kubectl get configmap cluster-autoscaler-status -n kube-system -o yaml

# Verify autoscaler is enabled on the node pool
az aks nodepool show -g <rg> --cluster-name <cluster> -n <nodepool> \
  --query "{autoscaleEnabled:enableAutoScaling, min:minCount, max:maxCount}"

Autoscaler won't scale up - common reasons:

• Node pool already at maxCount
• VM quota exhausted: az vm list-usage -l <region> -o table | grep -i "DSv3\|quota"
• Pod nodeAffinity is unsatisfiable on any new node template
• 10-minute cooldown period still active after last scale event

Autoscaler won't scale down - common reasons:

• Pods with emptyDir local storage (configure --skip-nodes-with-local-storage=false if safe)
• Standalone pods with no controller (not in a ReplicaSet)
• cluster-autoscaler.kubernetes.io/safe-to-evict: "false" annotation on a pod

Manual Scaling

az aks nodepool scale -g <rg> --cluster-name <cluster> -n <nodepool> --node-count <n>

Resource Pressure & Capacity Planning

Check actual vs allocatable:

kubectl describe node <node> | grep -A6 "Allocated resources:"

See AKS resource reservations for allocatable math.

Ephemeral storage pressure:

# Check what's consuming ephemeral storage on a node
kubectl debug node/<node> -it --image=mcr.microsoft.com/cbl-mariner/base/core:2.0

Common culprit: high-volume container logs accumulating in /var/log/containers.

Detailed Node And Cluster Guides

• Upgrade Operations for node images, Kubernetes version upgrades, surge settings, and PDB-related drain blockers.
• Spot And Zone Issues for spot evictions, tolerations, zone skew, and zonal storage or service behavior.