Diagnosing cluster issues

This page explains how to use the gkectl command-line interface (CLI) tool in Google Distributed Cloud to diagnose issues in your clusters.

Overview

The gkectl tool has two commands for troubleshooting issues with clusters: gkectl diagnose cluster and gkectl diagnose snapshot. The commands work with both admin and user clusters.

gkectl diagnose cluster

Performs health checks on your cluster and reports errors. Runs health checks on the following components:

• VCenter
  • Credential
  • DRS
  • Anti Affinity Groups
  • Network
  • Version
  • Datacenter
  • Datastore
  • ResourcePool
  • Folder
  • Network
• Loadbalancer (F5, Seesaw, Manual)
• User cluster and node pools
• Cluster objects
• Machine objects and the corresponding cluster nodes
• Pods in the kube-system and gke-system namespaces
• User control plane if the target cluster is a user cluster
• vSphere persistent volumes in the cluster
• User and admin cluster vCPU (virtual CPU) and memory contention signals
• User and admin cluster ESXi preconfigured Host CPU Usage and Memory Usage alarms.

gkectl diagnose snapshot

Compresses a cluster's status, configurations, and logs into a tarball file. Specifically, the default configuration of the command captures the following information about your cluster:

• Kubernetes version

• Status of Kubernetes resources in the kube-system and gke-system namespaces: cluster, machine, nodes, Services, Endpoints, ConfigMaps, ReplicaSets, CronJobs, Pods, and the owners of those Pods, including Deployments, DaemonSets, and StatefulSets

• Status of the user control plane if the target cluster is a user cluster (the user cluster's control plane runs in the admin cluster)

• Details about each node configuration including IP addresses, iptables rules, mount points, file system, network connections, and running processes

• Container logs from the admin cluster's control-plane node, when Kubernetes API server is not available

• vSphere information including VM objects and their Events based on Resource Pool. Also Datacenter, Cluster, Network, and Datastore objects associated with VMs

• F5 BIG-IP load balancer information including virtual server, virtual address, pool, node, and monitor

• Logs from the gkectl diagnose snapshot command

• An HTML index file for all of the files in the snapshot

• Optionally, the cluster configuration file used to install and upgrade the cluster

Credentials, including vSphere and F5 credentials, are removed before the tarball is created.

Diagnosing clusters

You can run gke diagnose cluster to look for common issues with your cluster.

Note: The --kubeconfig flag should always point to the admin cluster's kubeconfig file. gkectl diagnose returns an error if you provide the user cluster's kubeconfig.

Note: When there is a VIP issue with the targeting cluster, use --config to provide the admin cluster configuration file. That gives you more debugging information.

gkectl diagnose cluster --kubeconfig ADMIN_CLUSTER_KUBECONFIG --config ADMIN_CLUSTER_CONFIG

Example output:

Failed to access the api server via LB VIP "...": ...
Try to use the admin master IP instead of problematic VIP...
Reading config with version "[CONFIG_VERSION]"
Finding the admin master VM...
Fetching the VMs in the resource pool "[RESOURCE_POOL_NAME]"...
Found the "[ADMIN_MASTER_VM_NAME]" is the admin master VM.
Diagnosing admin|user cluster "[TARGET_CLUSTER_NAME]"...
...

Diagnosing an admin cluster

You can diagnose an admin cluster by passing in its name or by only passing in its kubeconfig.

Using admin cluster kubeconfig

Passing in the admin cluster's kubeconfig causes gkectl to automatically choose the admin cluster:

gkectl diagnose cluster --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG]

Using admin cluster name

To get the admin cluster's name, run the following command:

kubectl get cluster --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG]

Then, pass in the admin cluster name to gkectl diagnose cluster:

gkectl diagnose cluster --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[ADMIN_CLUSTER_NAME]

If your admin cluster is functioning properly, gkectl diagnose cluster returns output similar to the following:

Diagnosing admin cluster "[ADMIN_CLUSTER_NAME]" ...
- Validation Category: Admin Cluster Vcenter
Checking Credentials...SUCCESS
Checking DRS enabled...SUCCESS
Checking Hosts for AntiAffinityGroups...SUCCESS
Checking VSphere CSI Driver...SUCCESS
Checking Version...SUCCESS
Checking Datacenter...SUCCESS
Checking Datastore...SUCCESS
Checking Resource pool...SUCCESS
Checking Folder...SUCCESS
Checking Network...SUCCESS
Checking Node Pool Datastore...SUCCESS
- Validation Category: Admin Cluster
Checking Cluster Object...SUCCESS
Checking Machine Deployment...SUCCESS
Checking Machineset...SUCCESS
Checking Machine Objects...SUCCESS
Checking Control Plane Pods...SUCCESS
Checking [NAMESPACES] Pods...SUCCESS
Checking Storage...SUCCESS
Checking Resource...SUCCESS
Cluster is healthy.

Diagnosing a user cluster

To diagnose a cluster, first get the user cluster's name:

kubectl get cluster --kubeconfig=[USER_CLUSTER_KUBECONFIG]

Then, pass in the admin cluster's kubeconfig and the user cluster's name:

gkectl diagnose cluster --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
  --cluster-name=[USER_CLUSTER_NAME]

Note: gkectl diagnose returns an error if you provide the user cluster's kubeconfig.

If your user cluster is functioning properly, gkectl diagnose cluster returns output similar to the following:

I0314 01:57:44.232006 2134732 console.go:47] WARNING: SYLLOGI_FEATURE_GATES is deprecated, use GKE_ON_PREM_FEATURE_GATES to set the feature gate instead.
WARNING: SYLLOGI_FEATURE_GATES is deprecated, use GKE_ON_PREM_FEATURE_GATES to set the feature gate instead.
Preparing for the diagnose tool...
Diagnosing the cluster......  DONE

- Validation Category: User Cluster F5 BIG-IP
Checking f5 (credentials, partition)...SUCCESS

- Validation Category: User Cluster VCenter
Checking Credentials...SUCCESS
Checking DRS enabled...SUCCESS
Checking Hosts for AntiAffinityGroups...SUCCESS
Checking VSphere CSI Driver...SUCCESS
Checking Version...SUCCESS
Checking Datacenter...SUCCESS
Checking Datastore...SUCCESS
Checking Resource pool...SUCCESS
Checking Folder...SUCCESS
Checking Network...SUCCESS

- Validation Category: User Cluster
Checking user cluster and node pools...SUCCESS
Checking cluster object...SUCCESS
Checking machine deployment...SUCCESS
Checking machineset...SUCCESS
Checking machine objects...SUCCESS
Checking control plane pods...SUCCESS
Checking kube-system pods...SUCCESS
Checking gke-system pods...SUCCESS
Checking config-management-system pods...SUCCESS
Checking storage...SUCCESS
Checking resource...SUCCESS
Checking virtual machine resource contention...SUCCESS
Checking host resource contention...SUCCESS
Cluster is healthy.
Diagnose result is saved successfully in diagnose-user-cluster-20210314015803.json

Troubleshooting diagnosed cluster issues

If you have the following issues when running the gke diagnose cluster command, here are some possible resolutions.

.

Issue	Possible causes	Resolution
Kubernetes API server is not reachable, either for the admin cluster, or for user clusters.	Check the virtual machine health OOB (out-of-box) memory latency graphs, which ideally should have a memory latency around zero. Memory contention can also increase CPU contention, and the CPU readiness graphs might have a spike as there will be swapping involved.	Increase physical memory. For other options, see VMware troubleshooting suggestions.
Nodepool creation times out.	VMDK high read/write latency. Check VM health OOB for virtual disk read and write latency. According to VMware, a total latency greater than 20ms indicates a problem.	See VMware solutions for disk performance problems.

Capturing cluster state

If gkectl diagnose cluster finds errors, you should capture the cluster's state and provide the information to Google. You can do so using the gkectl diagnose snapshot command.

gkectl diagnose snapshot has an optional flag, --config. In addition to collecting information about the cluster, this flag collects the Google Distributed Cloud configuration file that was used to create or upgrade the cluster.

Note: The --kubeconfig flag should always point to the admin cluster's kubeconfig file. gkectl diagnose returns an error if you provide the user cluster's kubeconfig.

Capturing admin cluster state

To capture an admin cluster's state, run the following command, where --config is optional:

gkectl diagnose snapshot --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] [--config]

Note: When there is a VIP issue with the targeting cluster, use --config to provide the admin cluster configuration file. That gives you more debugging information.

The output includes a list of files and the name of a tarball file:

Taking snapshot of admin cluster "[ADMIN_CLUSTER_NAME]"...
   Using default snapshot configuration...
   Setting up "[ADMIN_CLUSTER_NAME]" ssh key file...DONE
   Taking snapshots...
       commands/kubectl_get_pods_-o_yaml_--kubeconfig_...env.default.kubeconfig_--namespace_kube-system
       commands/kubectl_get_deployments_-o_yaml_--kubeconfig_...env.default.kubeconfig_--namespace_kube-system
       commands/kubectl_get_daemonsets_-o_yaml_--kubeconfig_...env.default.kubeconfig_--namespace_kube-system
       ...
       nodes/[ADMIN_CLUSTER_NODE]/commands/journalctl_-u_kubelet
       nodes/[ADMIN_CLUSTER_NODE]/files/var/log/startup.log
       ...
   Snapshot succeeded. Output saved in [TARBALL_FILE_NAME].tar.gz.

To extract the tarball file to a directory, run the following command:

tar -zxf [TARBALL_FILE_NAME] --directory [EXTRACTION_DIRECTORY_NAME]

To look at the list of files produced by the snapshot, run the following commands:

cd [EXTRACTION_DIRECTORY_NAME]/[EXTRACTED_SNAPSHOT_DIRECTORY]
ls kubectlCommands
ls nodes/[NODE_NAME]/commands
ls nodes/[NODE_NAME]/files

To see the details of a particular operation, open one of the files.

Specifying the SSH key for the admin cluster

When you get a snapshot of the admin cluster, gkectl finds the private SSH key for the admin cluster automatically. You can also specify the key explicitly by using the --admin-ssh-key-path parameter.

Follow the instructions for Using SSH to connect to a cluster node to download the SSH keys.

Then in your gkectl diagnose snapshot command, set --admin-ssh-key-path to your decoded key file path:

gkectl diagnose snapshot --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--admin-ssh-key-path=[PATH_TO_DECODED_KEY]

Capturing user cluster state

To capture a user cluster's state, run the following command:

gkectl diagnose snapshot --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[USER_CLUSTER_NAME]

The output includes a list of files and the name of a tarball file:

Taking snapshot of user cluster "[USER_CLUSTER_NAME]"...
Using default snapshot configuration...
Setting up "[USER_CLUSTER_NAME]" ssh key file...DONE
    commands/kubectl_get_pods_-o_yaml_--kubeconfig_...env.default.kubeconfig_--namespace_user
    commands/kubectl_get_deployments_-o_yaml_--kubeconfig_...env.default.kubeconfig_--namespace_user
    commands/kubectl_get_daemonsets_-o_yaml_--kubeconfig_...env.default.kubeconfig_--namespace_user
    ...
    commands/kubectl_get_pods_-o_yaml_--kubeconfig_.tmp.user-kubeconfig-851213064_--namespace_kube-system
    commands/kubectl_get_deployments_-o_yaml_--kubeconfig_.tmp.user-kubeconfig-851213064_--namespace_kube-system
    commands/kubectl_get_daemonsets_-o_yaml_--kubeconfig_.tmp.user-kubeconfig-851213064_--namespace_kube-system
    ...
    nodes/[USER_CLUSTER_NODE]/commands/journalctl_-u_kubelet
    nodes/[USER_CLUSTER_NODE]/files/var/log/startup.log
    ...
Snapshot succeeded. Output saved in [FILENAME].tar.gz.

Snapshot scenarios

The gkectl diagnose snapshot command supports four scenarios. To specify a scenario, use the --scenario flag. The following list shows the possible values:

• system: (default) Collect a snapshot for the system namespaces: kube-system and gke-system.

• system-with-logs: Collect a system snapshot with logs.

• all: Collect a snapshot for all namespaces.

• all-with-logs: Collect an all snapshot with logs.

You can use each of the four scenarios with an admin cluster or a user cluster, so there are eight possible permutations. The following examples show some of the possibilities.

To create a snapshot of the admin cluster using the system scenario:

gkectl diagnose snapshot \
--kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--scenario=system

To create a snapshot of a user-cluster using the system-with-logs scenario:

gkectl diagnose snapshot \
--kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[USER_CLUSTER_NAME] \
--scenario=system-with-logs

To create a snapshot of a user cluster using the all scenario:

gkectl diagnose snapshot \
--kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[USER_CLUSTER_NAME] \
--scenario=all

To create a snapshot of the admin cluster using the all-with-logs scenario:

gkectl diagnose snapshot \
--kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--scenario=all-with-logs

Using --log-since to limit a snapshot

In the system-with-logs and all-with-logs scenarios, you can use the --log-since flag to limit log collection to a recent time period. For example, you could collect only the logs from the last two days or the last three hours. By default, diagnose snapshot collects all logs.

To limit the time period for log collection:

gkectl diagnose snapshot --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[CLUSTER_NAME] \
--scenario=system-with-logs \
--log-since=[DURATION]

Replace [DURATION] with a time value like 120m or 48h.

Notes:

• The --log-since flag is supported only for kubectl and journalctl logs.
• Command flags like --log-since are not allowed in the customized snapshot configuration.

Performing a dry run for a snapshot

You can use the --dry-run flag to show the actions to be taken and the snapshot configuration.

To perform a dry run on your admin cluster, enter the following command:

gkectl diagnose snapshot --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[ADMIN_CLUSTER_NAME] \
--dry-run

To perform a dry run on a user cluster, enter the following command:

gkectl diagnose snapshot --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[USER_CLUSTER_NAME] \
--dry-run

Using a snapshot configuration

If the four scenarios don't meet your needs, you can create a customized snapshot by passing in a snapshot configuration file using the --snapshot-config flag:

gkectl diagnose snapshot --kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[USER_CLUSTER_NAME] \
--snapshot-config=[SNAPSHOT_CONFIG_FILE]

Generating a snapshot configuration

You can generate a snapshot configuration for a given scenario by passing in the --scenario and --dry-run flags. For example, to see the snapshot configuration for the default scenario (system) of a user cluster, enter the following command:

gkectl diagnose snapshot \
--kubeconfig=[ADMIN_CLUSTER_KUBECONFIG] \
--cluster-name=[USER_CLUSTER_NAME] \
--scenario=system
--dry-run

The output is similar to the following:

numOfParallelThreads: 10
excludeWords:
- password
kubectlCommands:
- commands:
  - kubectl get clusters -o wide
  - kubectl get machines -o wide
  - kubectl get clusters -o yaml
  - kubectl get machines -o yaml
  - kubectl describe clusters
  - kubectl describe machines
  namespaces:
  - default
- commands:
  - kubectl version
  - kubectl cluster-info
  - kubectl get nodes -o wide
  - kubectl get nodes -o yaml
  - kubectl describe nodes
  namespaces: []
- commands:
  - kubectl get pods -o wide
  - kubectl get deployments -o wide
  - kubectl get daemonsets -o wide
  - kubectl get statefulsets -o wide
  - kubectl get replicasets -o wide
  - kubectl get services -o wide
  - kubectl get jobs -o wide
  - kubectl get cronjobs -o wide
  - kubectl get endpoints -o wide
  - kubectl get configmaps -o wide
  - kubectl get pods -o yaml
  - kubectl get deployments -o yaml
  - kubectl get daemonsets -o yaml
  - kubectl get statefulsets -o yaml
  - kubectl get replicasets -o yaml
  - kubectl get services -o yaml
  - kubectl get jobs -o yaml
  - kubectl get cronjobs -o yaml
  - kubectl get endpoints -o yaml
  - kubectl get configmaps -o yaml
  - kubectl describe pods
  - kubectl describe deployments
  - kubectl describe daemonsets
  - kubectl describe statefulsets
  - kubectl describe replicasets
  - kubectl describe services
  - kubectl describe jobs
  - kubectl describe cronjobs
  - kubectl describe endpoints
  - kubectl describe configmaps
  namespaces:
  - kube-system
  - gke-system
  - gke-connect.*
prometheusRequests: []
nodeCommands:
- nodes: []
  commands:
  - uptime
  - df --all --inodes
  - ip addr
  - sudo iptables-save --counters
  - mount
  - ip route list table all
  - top -bn1
  - sudo docker ps -a
  - ps -edF
  - ps -eo pid,tid,ppid,class,rtprio,ni,pri,psr,pcpu,stat,wchan:14,comm,args,cgroup
  - sudo conntrack --count
nodeFiles:
- nodes: []
  files:
  - /proc/sys/fs/file-nr
  - /proc/sys/net/nf_conntrack_max
seesawCommands: []
seesawFiles: []
nodeCollectors:
- nodes: []
f5:
  enabled: true
vCenter:
  enabled: true

• numOfParallelThreads: Number of parallel threads used to take snapshots.

• excludeWords: List of words to be excluded from the snapshot (case insensitive). Lines containing these words are removed from snapshot results. "password" is always excluded, whether or not you specify it.

• kubectlCommands: List of kubectl commands to run. The results are saved. The commands run against the corresponding namespaces. For kubectl logs commands, all Pods and containers in the corresponding namespaces are added automatically. Regular expressions are supported for specifying namespaces. If you do not specify a namespace, the default namespace is assumed.

• nodeCommands: List of commands to run on the corresponding nodes. The results are saved. When nodes are not specified, all nodes in the target cluster are considered.

• nodeFiles: List of files to be collected from the corresponding nodes. The files are saved. When nodes are not specified, all nodes in the target cluster are considered.

• seesawCommands: List of commands to run to collect Seesaw load balancer information. The results are saved if the cluster is using the Seesaw load balancer.

• seesawFiles: List of files to be collected for the Seesaw load balancer.

• nodeCollectors: A collector running for Cilium nodes to collect eBPF information.

• f5: A flag to enable the collecting of information related to the F5 BIG-IP load balancer.

• vCenter: A flag to enable the collecting of information related to vCenter.

• prometheusRequests: List of Prometheus requests. The results are saved.

Known issues

Version 1.1.2-gke.0: path resolves to multiple datacenters

Refer to Google Distributed Cloud release notes.

Versions 1.1.x: Volume not attached to machine

Refer to Google Distributed Cloud release notes.