Upgrade notes
This page is intended to deal with specific, special circumstances you may encounter when upgrading between versions of Charmed Kubernetes. The notes are organised according to the upgrade path below, but also be aware that any upgrade that spans more than one minor version may need to beware of notes in any of the intervening steps.
Upgrading to 1.15
This upgrade switches the container runtime to make use of containerd, rather
than Docker. You have the option of keeping Docker as the container runtime,
but even in that case you must perform the upgrade steps. To facilitate
different container runtimes, the architecture of Charmed Kubernetes has
changed slightly, and the container runtime is now part of a separate,
subordinate charm rather than being included in the kubernetes-master and
kubernetes-worker charms.
To keep Docker as the container runtime
Docker is currently installed on your kubernetes-worker units. The Docker subordinate charm includes clean-up code to manage the transition to the new pluggable architecture. To upgrade whilst retaining Docker as the runtime, you need to additionally deploy the new charm and add relations to the master and worker components:
juju deploy cs:~containers/docker
juju add-relation docker kubernetes-master
juju add-relation docker kubernetes-worker
The upgrade is complete, and your worker nodes will continue to use the Docker runtime. For information on configuring the Docker charm, see the Docker configuration page.
To migrate to containerd
If you intend to switch to containerd, it’s recommended that you first add some temporary extra worker units. While not strictly necessary, skipping this step will result in some cluster down time. Adding temporary additional workers provides a place for keeping pods running while new workers are brought online. The temporary workers can then be removed as the pods are migrated to the new workers. The rest of these instructions assume that you have deployed temporary workers.
Deploy temporary workers
CURRENT_WORKER_REV=$(juju status | grep '^kubernetes-worker\s' | awk '{print $7}')
CURRENT_WORKER_COUNT=$(juju status | grep '^kubernetes-worker/' | wc -l | sed -e 's/^[ \t]*//')
juju deploy cs:~containers/kubernetes-worker-$CURRENT_WORKER_REV kubernetes-worker-temp -n $CURRENT_WORKER_COUNT
Add necessary relations
juju status --relations | grep worker: | awk '{print $1,$2}' | sed 's/worker:/worker-temp:/g' | xargs -n2 juju relate
Wait for the temporary workers to become active before continuing. Upgrade the master and worker charms:
juju upgrade-charm kubernetes-master
juju upgrade-charm kubernetes-worker
The kubernetes-worker units will enter a blocked state, with status message “Connect a container runtime.”
Deploy and relate the new Docker charm
This step is needed even if you do not intend to use Docker following the
upgrade. Docker is already installed on your kubernetes-worker units, and
the Docker subordinate includes clean-up code to uninstall Docker when the
Docker charm is replaced with the containerd charm.
juju deploy cs:~containers/docker
juju add-relation docker kubernetes-master
juju add-relation docker kubernetes-worker
Switching to Containerd
Now, pause the existing workers, which will move pods to the temporary workers.
juju run-action [unit] pause --wait
For example:
juju run-action kubernetes-worker/0 pause --wait
juju run-action kubernetes-worker/1 pause --wait
juju run-action kubernetes-worker/2 pause --wait
One-liner:
juju status | grep ^kubernetes-worker/ | awk '{print $1}' | tr -d '*' | xargs -n1 -I '{}' juju run-action {} pause --wait
Remove Docker
This will uninstall Docker from the workers.
juju remove-relation docker kubernetes-master
juju remove-relation docker kubernetes-worker
juju remove-application docker
Deploy Containerd
juju deploy cs:~containers/containerd
juju add-relation containerd kubernetes-master
juju add-relation containerd kubernetes-worker
Resume workers
Now we can allow pods to be rescheduled to our original workers.
juju run-action [unit] resume --wait
E.g.
juju run-action kubernetes-worker/0 resume --wait
juju run-action kubernetes-worker/1 resume --wait
juju run-action kubernetes-worker/2 resume --wait
One-liner:
juju status | grep ^kubernetes-worker/ | awk '{print $1}' | tr -d '*' | xargs -n1 -I '{}' juju run-action {} resume --wait
Cleanup
You can now pause the temporary workers to force all pods to migrate back to your “real” workers, then remove the temporary workers.
juju status | grep ^kubernetes-worker-temp/ | awk '{print $1}' | tr -d '*' | xargs -n1 -I '{}' juju run-action {} pause --wait
juju remove-application kubernetes-worker-temp
Mixing Containerd and Docker
Once you have a Containerd backed CDK running, you can add Docker backed workers like so:
juju deploy cs:~containers/kubernetes-worker kubernetes-worker-docker
juju deploy cs:~containers/docker
juju relate docker kubernetes-worker-docker
Upgrading to 1.14
This upgrade includes support for CoreDNS 1.4.0. All new deployments of Charmed Kubernetes will install CoreDNS by default instead of KubeDNS.
Existing deployments which are upgraded to CDK 1.14 will continue to use KubeDNS until the operator chooses to upgrade to CoreDNS. To upgrade, set the new dns-provider config:
juju config kubernetes-master dns-provider=core-dns
Please be aware that changing DNS providers will momentarily interrupt DNS availability within the cluster. It is not necessary to recreate pods after the upgrade completes.
The enable-kube-dns option has been removed to avoid confusion. The new
dns-provider option allows you to enable or disable KubeDNS as needed.
For more information on the new dns-provider config, see the
dns-provider config description.
Upgrading from 1.9.x to 1.10.x
This upgrade includes a transistion between major versions of etcd, from 2.3 to 3.x. Between these releases, etcd changed the way it accesses storage, so it is necessary to reconfigure this. There is more detailed information on the change and the upgrade proceedure in the upstream etcd documentation.
Caution: This upgrade must be completed before attempting to upgrade the running cluster.
To make this upgrade more convenient for users of CDK, a script has been prepared to manage the transition. The script can be examined here.
To use the script to update etcd, follow these steps:
1. Download the script with the command:
curl -O https://raw.githubusercontent.com/juju-solutions/cdk-etcd-2to3/master/migrate
2. Make the script executable:
chmod +x migrate
3. Execute the script:
./migrate
4. etcd OutputSed
The script should update etcd and you will see output similar to the following:
· Waiting for etcd units to be active and idle...
· Acquiring configured version of etcd...
· Upgrading etcd to version 3.0/stable from 2.3/stable.
· Waiting for etcd upgrade to 3.0/stable............................................................
· Waiting for etcd units to be active and idle....................................................
· Waiting for etcd cluster convergence...
· Stopping all Kubernetes api servers...
· Waiting for etcd cluster convergence...
· Stopping etcd...
· Migrating etcd/0...
· Migrating etcd/1...
· Migrating etcd/2...
· Starting etcd...
· Configuring storage-backend to etcd3...
· Waiting for all Kubernetes api servers to restart.......
· Done.
You can now proceed with the rest of the upgrade.