Upgrading Consul on Kubernetes Components

Upgrade types

We recommend updating Consul on Kubernetes when:

You change your Helm configuration
A new Helm chart is released
You want to upgrade your Consul version.

Helm configuration changes

If you make a change to your Helm values file, you need to perform a helm upgrade for those changes to take effect.

For example, if you installed Consul with connectInject.enabled: false and you want to change its value to true:

Determine your current installed chart version.

$ helm list --filter consul --namespace consul
NAME    NAMESPACE   REVISION    UPDATED                                 STATUS      CHART           APP VERSION
consul  consul      2           2022-02-02 21:49:45.647678 -0800 PST    deployed    consul-0.40.0   1.11.2

In this example, version 0.40.0 (from consul-k8s:0.40.0) is being used, and Consul on Kubernetes is installed in the consul namespace.

Perform a helm upgrade:
```
$ helm upgrade consul hashicorp/consul --namespace consul --version 0.40.0 --values /path/to/my/values.yaml
```
Before performing the upgrade, be sure you read the other sections on this page, continuing at Determine scope of changes.

Note: You should always set the --version flag when upgrading Helm. Otherwise, Helm uses the most up-to-date version in its local cache, which may result in an unintended upgrade.

Upgrade Helm chart version

You may wish to upgrade your Helm chart version to take advantage of new features and bug fixes, or because you want to upgrade your Consul version and it requires a certain Helm chart version.

Update your local Helm repository cache:
```
$ helm repo update
```

List all available versions. Here you can observe that the latest version of 0.40.0.

$ helm search repo hashicorp/consul --versions
NAME                CHART VERSION   APP VERSION DESCRIPTION
hashicorp/consul    0.40.0          1.11.2      Official HashiCorp Consul Chart
hashicorp/consul    0.39.0          1.11.1      Official HashiCorp Consul Chart
hashicorp/consul    0.38.0          1.10.4      Official HashiCorp Consul Chart
hashicorp/consul    0.37.0          1.10.4      Official HashiCorp Consul Chart
...

To determine which version you have installed, issue the following command:

$ helm list --filter consul --namespace consul
NAME    NAMESPACE   REVISION    UPDATED                                 STATUS      CHART           APP VERSION
consul  consul      2           2022-02-02 21:49:45.647678 -0800 PST    deployed    consul-0.39.0   1.11.1

In this example, version 0.39.0 (from consul-k8s:0.39.0) is being used.

If you want to upgrade to the latest 0.40.0 version, use the following procedure:

Check the changelog for any breaking changes from that version and any versions in between: CHANGELOG.md.
Upgrade by performing a helm upgrade with the --version flag:
```
$ helm upgrade consul hashicorp/consul --namespace consul --version 0.40.0 --values /path/to/my/values.yaml
```
Before performing the upgrade, be sure you've read the other sections on this page, continuing at Determine scope of changes.

Upgrade Consul version

If a new version of Consul is released, you need to perform a Helm upgrade to update to the new version. Before you upgrade to a new version:

Read the Upgrading Consul documentation.
Read any specific instructions for the version you want to upgrade to, as well as the Consul changelog for that version.
Read our Compatibility Matrix to ensure your current Helm chart version supports this Consul version. If it does not, you may need to also upgrade your Helm chart version at the same time.
Set global.image in your values.yaml to the desired version:
values.yaml
```
global:
  image: consul:1.11.2
```

Determine the version of your exisiting Helm installation. In this example, version 0.39.0 (from consul-k8s:0.39.0) is being used.

$ helm list --filter consul --namespace consul
NAME    NAMESPACE   REVISION    UPDATED                                 STATUS      CHART           APP VERSION
consul  consul      2           2022-02-02 21:49:45.647678 -0800 PST    deployed    consul-0.39.0   1.11.1

Perform a helm upgrade:
```
$ helm upgrade consul hashicorp/consul --namespace consul --version 0.39.0 --values /path/to/my/values.yaml
```
Before performing the upgrade, be sure you have read the other sections on this page, continuing at Determine scope of changes.

Note: You should always set the --version flag when upgrading Helm. Otherwise, Helm uses the most up-to-date version in its local cache, which may result in an unintended upgrade.

Determine scope of changes

Before upgrading, it is important to understand the changes that affect your cluster. For example, you need to take more care if your upgrade results in the Consul server StatefulSet being redeployed.

There is no built-in functionality in Helm that shows what a helm upgrade changes. There is, however, a Helm plugin helm-diff that can be used.

Install helm-diff with:

$ helm plugin install https://github.com/databus23/helm-diff

If you are updating your values.yaml file, do so now.
Take the same helm upgrade command you were planning to issue but perform helm diff upgrade instead of helm upgrade:
```
$ helm diff upgrade consul hashicorp/consul --namespace consul --version 0.40.0 --values /path/to/your/values.yaml
```
This command prints out the manifests that will be updated and their diffs.

To see only updated objects, add | grep "has changed":

$ helm diff upgrade consul hashicorp/consul --namespace consul --version 0.40.0 --values /path/to/your/values.yaml |
  grep "has changed"

Take specific note if consul-server, StatefulSet is listed, as it means your Consul server statefulset will be redeployed.
If your Consul server statefulset needs to be redeployed, follow the same pattern for upgrades as on other platforms by redploying servers one by one. Refer tp Upgrading Consul for more information.
If neither the server statefulset is not being redeployed, then you can continue with the Helm upgrade without any specific sequence to follow.

Upgrade Consul servers

Initiate the server upgrade:

Change the global.image value to the desired Consul version.
Set the server.updatePartition value to the number of server replicas. By default, there are 3 servers, so you would set this value to 3.
Set the updateStrategy for clients to OnDelete.
values.yaml
```
global:
  image: 'consul:123.456'
server:
  updatePartition: 3
```
The updatePartition value controls how many instances of the server cluster are updated. Only instances with an index greater than the updatePartition value are updated (zero-indexed). Therefore, by setting it equal to replicas, updates should not occur immediately.
Next, perform the upgrade:
```
$ helm upgrade consul hashicorp/consul --namespace consul --version <your-version> --values /path/to/your/values.yaml
```
This command does not cause the servers to redeploy, although the resource is updated. If everything is stable, decrease the updatePartition value by one and performing helm upgrade again. This will cause the first Consul server to be stopped and restarted with the new image.
Wait until the Consul server cluster is healthy again (30s to a few minutes). This can be confirmed by issuing consul members on one of the previous servers, and ensuring that all servers are listed and are alive.
Decrease updatePartition by one and upgrade again. Continue until updatePartition is 0. At this point, you may remove the updatePartition configuration. Your server upgrade is complete.

Upgrading to Consul Dataplane

In earlier versions, Consul on Kubernetes used client agents in its deployments. As of v1.14.0, Consul uses Consul Dataplane in Kubernetes deployments instead of client agents.

If you upgrade Consul from a version that uses client agents to a version the uses dataplanes, complete the following steps to upgrade your deployment safely and without downtime.

Before you upgrade, edit your Helm chart to enable Consul client agents by setting client.enabled and client.updateStrategy:
```
client:
    enabled: true
    updateStrategy: |
      type: OnDelete
```
Add consul.hashicorp.com/consul-k8s-version: 1.0.0 to the annotations for each pod you upgrade.
Follow our recommended procedures to upgrade servers on Kubernetes deployments to upgrade Helm values for the new version of Consul.
Run kubectl rollout restart to restart your service mesh applications. Restarting service mesh application causes Kubernetes to re-inject them with the webhook for dataplanes.
Restart all gateways in your service mesh.
Disable client agents in your Helm chart by deleting the client stanza or setting client.enabled to false.

Configuring TLS on an existing cluster

If you already have a Consul cluster deployed on Kubernetes and would like to turn on TLS for internal Consul communication, refer to Configuring TLS on an Existing Cluster.