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Nodes and Clusters

This page covers common debugging scenarios for nodes and clusters after they have been deployed.

Nodes​

Scenario - Repaved Nodes​

Palette performs a rolling upgrade on nodes when it detects a change in the kubeadm config. Below are some actions that cause the kubeadm configuration to change and result in nodes being upgraded:

  • OS layer changes
  • Kubernetes layer changes
  • Kubernetes version upgrade
  • Kubernetes control plane upsize
  • Machine pool updates for disk size
  • Changes in availability zones
  • Changes in instance types

Logs are provided in Palette for traceability. However, these logs may be lost when the pods are relaunched. To ensure that the cause and context is persisted across repaving, refer to the status.upgrades: [] field in the in the SpectroCluster object in the /v1/dashboard/spectroclusters/:uid/overview API.

The following example shows the status.upgrades field for a cluster that had Kubernetes configuration changes that resulted in a node repave. The API payload is incomplete for brevity.

"upgrades": [
    {
        "reason": [
            "{v1beta1.KubeadmConfigSpec}.ClusterConfiguration.APIServer.ControlPlaneComponent.ExtraArgs[\"oidc-client-id\"] changed from <invalid reflect.Value> to xxxxxxxxxxx",
            "{v1beta1.KubeadmConfigSpec}.ClusterConfiguration.APIServer.ControlPlaneComponent.ExtraArgs[\"oidc-groups-claim\"] changed from <invalid reflect.Value> to groups",
            "{v1beta1.KubeadmConfigSpec}.ClusterConfiguration.APIServer.ControlPlaneComponent.ExtraArgs[\"oidc-issuer-url\"] changed from <invalid reflect.Value> to https://console.spectrocloud.com/v1/oidc/tenant/XXXXXXXXXXXX",
            "{v1beta1.KubeadmConfigSpec}.ClusterConfiguration.APIServer.ControlPlaneComponent.ExtraArgs[\"oidc-username-claim\"] changed from <invalid reflect.Value> to email"
        ],
        "timestamp": "2023-09-18T19:49:33.000Z"
    }
]

For detailed information, review the cluster upgrades page.


Clusters​

Scenario - vSphere Cluster and Stale ARP Table​

Sometimes vSphere clusters encounter issues where nodes with an assigned Virtual IP Address (VIP) cannot contact the node with a VIP. The problem is caused by Address Resolution Protocol (ARP) entries becoming stale on non-VIP nodes.

To minimize this situation, vSphere clusters deployed through Palette now have a daemon set that cleans the ARP entry cache every five minutes. The cleaning process forces the nodes to periodically re-request an ARP entry of the VIP node. This is done automatically without any user action.

You can verify the cleaning process by issuing the following command on non-VIP nodes and observing that the ARP cache is never older than 300 seconds.


watch ip -statistics neighbour

EKS Cluster Worker Pool Failures​

If your EKS cluster worker pool ends up in Failed, Create Failed or Error nodes failed to join state, refer to the Amazon EKS Runbook for troubleshooting guidance.


Palette Agents Workload Payload Size Issue​

A cluster comprised of many nodes can create a situation where the workload report data the agent sends to Palette exceeds the 1 MB threshold and fails to deliver the messages. If the agent encounters too many workload report deliveries, the agent container may transition into a CrashLoopBackOff state.

If you encounter this scenario, you can configure the cluster to stop sending workload reports to Palette. To disable the workload report feature, create a configMap with the following configuration. Use a cluster profile manifest layer to create the configMap.


apiVersion: v1
kind: ConfigMap
metadata:
  name: palette-agent-config
  namespace: "cluster-{{ .spectro.system.cluster.uid }}"
data:
  feature.workloads: disable

OS Patch Fails​

When conducting OS Patching, sometimes the patching process can time out and fail. This issue is due to some OS patches requiring GRUB packages. GRUB updates often require user prompts, and if a user prompt is required during the OS patching process, the patching process will fail.

Debug Steps​

To resolve this issue, use the following steps:

  1. Log in to Palette.

  2. From left Main Menu, select Clusters.

  3. Select the cluster that is experiencing the issue and click on its row to access the cluster details page.

  4. From the cluster details page, select the Nodes tab.

  5. Click on a cluster node to access its details page. Review the network information, such as the subnet and the network the node is in.

  6. Log in to the infrastructure provider console and acquire the node IP address.

  7. SSH into one of the cluster nodes and issue the following command.

rm /var/cache/debconf/config.dat && \
dpkg --configure -a
  1. A prompt may appear asking you to select the boot device. Select the appropriate boot device and press Enter.
tip

If you are unsure of the boot device, use a disk utility such as lsblk or fdisk to identify the boot device. Below is an example of using lsblk to identify the boot device. The output is abbreviated for brevity.

lsblk --output NAME,TYPE,MOUNTPOINT
NAME    TYPE MOUNTPOINT
fd0     disk
loop0   loop /snap/core20/1974
...
loop10  loop /snap/snapd/20092
loop11  loop /snap/snapd/20290
sda     disk
├─sda1  part /
├─sda14 part
└─sda15 part /boot/efi
sr0     rom

The highlighted line displays the boot device. In this example, the boot device is sda15, mounted at /boot/efi. The boot device may be different for your node.

  1. Repeat the previous step for all nodes in the cluster.