Troubleshooting
This document with highlighting how to troubleshoot the deployment of a Kubernetes cluster, it will not cover debugging of workloads inside Kubernetes.
- Before you begin
- Understanding Cluster Status
- SSHing to units
- Collecting debug information
- Common Problems
- Logging and monitoring
Before you begin
This page assumes you have a working Juju deployed cluster.
Understanding Cluster Status
Using juju status can give you some insight as to what’s happening in a cluster:
Model Controller Cloud/Region Version
kubes work-multi aws/us-east-2 2.0.2.1
App Version Status Scale Charm Store Rev OS Notes
easyrsa 3.0.1 active 1 easyrsa jujucharms 3 ubuntu
etcd 2.2.5 active 1 etcd jujucharms 17 ubuntu
flannel 0.6.1 active 2 flannel jujucharms 6 ubuntu
kubernetes-master 1.4.5 active 1 kubernetes-master jujucharms 8 ubuntu exposed
kubernetes-worker 1.4.5 active 1 kubernetes-worker jujucharms 11 ubuntu exposed
Unit Workload Agent Machine Public address Ports Message
easyrsa/0* active idle 0/lxd/0 10.0.0.55 Certificate Authority connected.
etcd/0* active idle 0 52.15.47.228 2379/tcp Healthy with 1 known peers.
kubernetes-master/0* active idle 0 52.15.47.228 6443/tcp Kubernetes master services ready.
flannel/1 active idle 52.15.47.228 Flannel subnet 10.1.75.1/24
kubernetes-worker/0* active idle 1 52.15.177.233 80/tcp,443/tcp Kubernetes worker running.
flannel/0* active idle 52.15.177.233 Flannel subnet 10.1.63.1/24
Machine State DNS Inst id Series AZ
0 started 52.15.47.228 i-0bb211a18be691473 xenial us-east-2a
0/lxd/0 started 10.0.0.55 juju-153b74-0-lxd-0 xenial
1 started 52.15.177.233 i-0502d7de733be31bb xenial us-east-2b
In this example we can glean some information. The Workload column will show the status of a given service. The Message section will show you the health of a given service in the cluster. During deployment and maintenance these workload statuses will update to reflect what a given node is doing. For example the workload my say maintenance while message will describe this maintenance as Installing docker.
During normal operation the Workload should read active, the Agent column (which reflects what the Juju agent is doing) should read idle, and the messages will either say Ready or another descriptive term. juju status --color will also return all green results when a cluster’s deployment is healthy.
Status can become unwieldy for large clusters, it is then recommended to check status on individual services, for example to check the status on the workers only:
juju status kubernetes-worker
or just on the etcd cluster:
juju status etcd
Errors will have an obvious message, and will return a red result when used with juju status --color. Nodes that come up in this manner should be investigated.
SSHing to units
You can ssh to individual units easily with the following convention, juju ssh <servicename>/<unit#>:
juju ssh kubernetes-worker/3
Will automatically ssh you to the 3rd worker unit.
juju ssh easyrsa/0
This will automatically ssh you to the easyrsa unit.
Collecting debug information
Sometimes it is useful to collect all the information from a cluster to share with a developer to identify problems. This is best accomplished with CDK Field Agent.
Download and execute the collect.py script from CDK Field Agent on a box that has a Juju client configured with the current controller and model pointing at the CDK deployment of interest.
Running the script will generate a tarball of system information and includes basic information such as systemctl status, Juju logs, charm unit data, etc. Additional application-specific information may be included as well.
Common Problems
Load Balancer interfering with Helm
This section assumes you have a working deployment of Kubernetes via Juju using a Load Balancer for the API, and that you are using Helm to deploy charts.
To deploy Helm you will have run:
helm init
$HELM_HOME has been configured at /home/ubuntu/.helm
Tiller (the helm server side component) has been installed into your Kubernetes Cluster.
Happy Helming!
Then when using helm you may see one of the following errors:
- Helm doesn’t get the version from the Tiller server
helm version
Client: &version.Version{SemVer:"v2.1.3", GitCommit:"5cbc48fb305ca4bf68c26eb8d2a7eb363227e973", GitTreeState:"clean"}
Error: cannot connect to Tiller
- Helm cannot install your chart
helm install <chart> --debug
Error: forwarding ports: error upgrading connection: Upgrade request required
This is caused by the API load balancer not forwarding ports in the context of the helm client-server relationship. To deploy using helm, you will need to follow these steps:
- Expose the Kubernetes Master service
juju expose kubernetes-master
- Identify the public IP address of one of your masters
juju status kubernetes-master
Model Controller Cloud/Region Version
production k8s-admin aws/us-east-1 2.0.0
App Version Status Scale Charm Store Rev OS Notes
flannel 0.6.1 active 1 flannel jujucharms 7 ubuntu
kubernetes-master 1.5.1 active 1 kubernetes-master jujucharms 10 ubuntu exposed
Unit Workload Agent Machine Public address Ports Message
kubernetes-master/0* active idle 5 54.210.100.102 6443/tcp Kubernetes master running.
flannel/0 active idle 54.210.100.102 Flannel subnet 10.1.50.1/24
Machine State DNS Inst id Series AZ
5 started 54.210.100.102 i-002b7150639eb183b xenial us-east-1a
Relation Provides Consumes Type
certificates easyrsa kubernetes-master regular
etcd etcd flannel regular
etcd etcd kubernetes-master regular
cni flannel kubernetes-master regular
loadbalancer kubeapi-load-balancer kubernetes-master regular
cni kubernetes-master flannel subordinate
cluster-dns kubernetes-master kubernetes-worker regular
cni kubernetes-worker flannel subordinate
In this context the public IP address is 54.210.100.102.
If you want to access this data programmatically you can use the JSON output:
juju show-status kubernetes-master --format json | jq --raw-output '.applications."kubernetes-master".units | keys[]'
54.210.100.102
- Update the kubeconfig file
Identify the kubeconfig file or section used for this cluster, and edit the server configuration.
By default, it will look like https://54.213.123.123:443. Replace it with the Kubernetes Master endpoint https://54.210.100.102:6443 and save.
Note that the default port used by CDK for the Kubernetes Master API is 6443 while the port exposed by the load balancer is 443.
- Start helm again!
helm install <chart> --debug
Created tunnel using local port: '36749'
SERVER: "localhost:36749"
CHART PATH: /home/ubuntu/.helm/<chart>
NAME: <chart>
...
...
Logging and monitoring
By default there is no log aggregation of the Kubernetes nodes, each node logs locally. Please read over the logging page for more information.