Upgrade Istio

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Canary upgrades

Upgrading Istio can be done by first running a canary deployment of the new control plane, allowing you to monitor the effect of the upgrade with a small percentage of the workloads, before migrating all of the traffic to the new version. This is much safer than doing an in place upgrade and is the recommended upgrade method.

When installing Istio, the revision installation setting can be used to deploy multiple independent control planes at the same time. A canary version of an upgrade can be started by installing the new Istio version’s control plane next to the old one, using a different revision setting. Each revision is a full Istio control plane implementation with its own Deployment, Service, etc.

Control plane

To install a new revision called canary, you would set the revision field as follows:

$ istioctl install --set revision=canary

After running the command, you will have two control plane deployments and services running side-by-side:

$ kubectl get pods -n istio-system -l app=istiod
NAME                                    READY   STATUS    RESTARTS   AGE
istiod-786779888b-p9s5n                 1/1     Running   0          114m
istiod-canary-6956db645c-vwhsk          1/1     Running   0          1m

$ kubectl get svc -n istio-system -l app=istiod
NAME            TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)                                                AGE
istiod          ClusterIP   10.32.5.247   <none>        15010/TCP,15012/TCP,443/TCP,15014/TCP                  33d
istiod-canary   ClusterIP   10.32.6.58    <none>        15010/TCP,15012/TCP,443/TCP,15014/TCP,53/UDP,853/TCP   12m

You will also see that there are two sidecar injector configurations including the new revision.

$ kubectl get mutatingwebhookconfigurations
NAME                            CREATED AT
istio-sidecar-injector          2020-03-26T07:09:21Z
istio-sidecar-injector-canary   2020-04-28T19:03:26Z

Data plane

Unlike istiod, Istio gateways do not run revision-specific instances, but are instead in-place upgraded to use the new control plane revision. You can verify that the istio-ingress gateway is using the canary revision by running the following command:

$ istioctl proxy-config endpoints $(kubectl -n istio-system get pod -l app=istio-ingressgateway -o jsonpath='{.items..metadata.name}').istio-system --cluster xds-grpc -ojson | grep hostname
"hostname": "istiod-canary.istio-system.svc"

However, simply installing the new revision has no impact on the existing sidecar proxies. To upgrade these, you must configure them to point to the new istiod-canary control plane. This is controlled during sidecar injection based on the namespace label istio.io/rev.

To upgrade the namespace test-ns, remove the istio-injection label, and add the istio.io/rev label to point to the canary revision. The istio-injection label must be removed because it takes precedence over the istio.io/rev label for backward compatibility.

$ kubectl label namespace test-ns istio-injection- istio.io/rev=canary

After the namespace updates, you need to restart the pods to trigger re-injection. One way to do this is using:

$ kubectl rollout restart deployment -n test-ns

When the pods are re-injected, they will be configured to point to the istiod-canary control plane. You can verify this by looking at the pod labels.

For example, the following command will show all the pods using the canary revision:

$ kubectl get pods -n test-ns -l istio.io/rev=canary

To verify that the new pods in the test-ns namespace are using the istiod-canary service corresponding to the canary revision, select one newly created pod and use the pod_name in the following command:

$ istioctl proxy-config endpoints ${pod_name}.test-ns --cluster xds-grpc -ojson | grep hostname
"hostname": "istiod-canary.istio-system.svc"

The output confirms that the pod is using istiod-canary revision of the control plane.

Uninstall old control plane

After upgrading both the control plane and data plane, you can uninstall the old control plane. For example, the following command uninstalls a control plane of revision 1-6-5:

$ istioctl x uninstall --revision 1-6-5

If the old control plane does not have a revision label, uninstall it using its original installation options, for example:

$ istioctl x uninstall -f manifests/profiles/default.yaml

Confirm that the old control plane has been removed and only the new one still exists in the cluster:

$ kubectl get pods -n istio-system -l app=istiod
NAME                             READY   STATUS    RESTARTS   AGE
istiod-canary-55887f699c-t8bh8   1/1     Running   0          27m

Note that the above instructions only removed the resources for the specified control plane revision, but not cluster-scoped resources shared with other control planes. To uninstall Istio completely, refer to the uninstall guide.

Uninstall canary control plane

If you decide to rollback to the old control plane, instead of completing the canary upgrade, you can uninstall the canary revision using istioctl x uninstall --revision=canary.

However, in this case you must first reinstall the gateway(s) for the previous revision manually, because the uninstall command will not automatically revert the previously in-place upgraded ones.

In place upgrades

The istioctl upgrade command performs an upgrade of Istio. Before performing the upgrade, it checks that the Istio installation meets the upgrade eligibility criteria. Also, it alerts the user if it detects any changes in the profile default values between Istio versions.

The upgrade command can also perform a downgrade of Istio.

See the istioctl upgrade reference for all the options provided by the istioctl upgrade command.

Upgrade prerequisites

Ensure you meet these requirements before starting the upgrade process:

Istio version is 1 minor version less than 1.7.4. For example, 1.6.0 or higher is required before you start the upgrade process to 1.7.0.
Your Istio installation was installed using istioctl.

Upgrade steps

The commands in this section should be run using the new version of istioctl which can be found in the bin/ subdirectory of the downloaded package.

Download the new Istio release and change directory to the new release directory.
Ensure that your Kubernetes configuration points to the cluster to upgrade:
```
$ kubectl config view
```
Begin the upgrade by running this command:
```
$ istioctl upgrade -f `<your-custom-configuration-file>`
```
If you installed Istio using the -f flag, for example istioctl install -f <IstioControlPlane-custom-resource-definition-file>, then you must provide the same -f flag value to the istioctl upgrade command.
istioctl upgrade does not support the --set flag. Therefore, if you installed Istio using the --set command, create a configuration file with the equivalent configuration options and pass it to the istioctl upgrade command using the -f flag instead.
If you omit the -f flag, Istio upgrades using the default profile.
After performing several checks, istioctl will ask you to confirm whether to proceed.
istioctl will in-place upgrade the Istio control plane and gateways to the new version and indicate the completion status.
After istioctl completes the upgrade, you must manually update the Istio data plane by restarting any pods with Istio sidecars:
```
$ kubectl rollout restart deployment
```

Downgrade prerequisites

Ensure you meet these requirements before starting the downgrade process:

Your Istio installation was installed using istioctl.
The Istio version you intend to downgrade to is 1 minor version less than 1.7.4.
Downgrade must be done using the istioctl binary version that corresponds to the Istio version that you intend to downgrade to. For example, if you are downgrading from Istio 1.7 to 1.6.5, use istioctl version 1.6.5.

Steps to downgrade to a lower Istio version

You can use istioctl upgrade to downgrade to a lower version of Istio. Please notice that you need to use the istioctl binary corresponding to the lower version (e.g., 1.6.5). The process steps are identical to the upgrade process mentioned in the previous section. When completed, the process will restore Istio back to the Istio version that was installed before.

istioctl install can be used to install an older version of the Istio control plane, but is not recommended because it does not perform any checks. For example, default values applied to the cluster for a configuration profile may change without warning.