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.

Before you upgrade

Before upgrading Istio, it is recommended to run the istioctl x precheck command to make sure the upgrade is compatible with your environment.

$ istioctl x precheck
✔ No issues found when checking the cluster. Istio is safe to install or upgrade!
  To get started, check out https://istio.io/latest/docs/setup/getting-started/

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-1-27-1-bdf5948d5-htddg    1/1     Running   0          47s
istiod-canary-84c8d4dcfb-skcfv   1/1     Running   0          25s

$ kubectl get svc -n istio-system -l app=istiod
NAME            TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                                 AGE
istiod-1-27-1   ClusterIP   10.96.93.151     <none>        15010/TCP,15012/TCP,443/TCP,15014/TCP   109s
istiod-canary   ClusterIP   10.104.186.250   <none>        15010/TCP,15012/TCP,443/TCP,15014/TCP   87s

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

$ kubectl get mutatingwebhookconfigurations
NAME                            WEBHOOKS   AGE
istio-sidecar-injector-1-27-1   2          2m16s
istio-sidecar-injector-canary   2          114s

data plane

Refer to Gateway Canary Upgrade to understand how to run revision specific instances of Istio gateway. In this example, since we use the default Istio profile, 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-status | grep "$(kubectl -n istio-system get pod -l app=istio-ingressgateway -o jsonpath='{.items..metadata.name}')" | awk -F '[[:space:]][[:space:]]+' '{print $8}'
istiod-canary-6956db645c-vwhsk

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.

Create a namespace test-ns with istio-injection enabled. In the test-ns namespace, deploy a sample curl pod:

1. Create a namespace test-ns.

   $ kubectl create ns test-ns

2. Label the namespace using istio-injection label.

   $ kubectl label namespace test-ns istio-injection=enabled

3. Bring up a sample curl pod in test-ns namespace.

   $ kubectl apply -n test-ns -f samples/curl/curl.yaml

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 restart all pods in namespace test-ns 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 using istioctl proxy-status.

$ istioctl proxy-status | grep "\.test-ns "

The output will show all pods under the namespace that are using the canary revision.

Stable revision labels

Usage

1. Install two revisions of control plane:

   $ istioctl install --revision=1-27-1 --set profile=minimal --skip-confirmation
   $ istioctl install --revision=1-28-0 --set profile=minimal --skip-confirmation

2. Create stable and canary revision tags and associate them to the respective revisions:

   $ istioctl tag set prod-stable --revision 1-27-1
   $ istioctl tag set prod-canary --revision 1-28-0

3. Label application namespaces to map to the respective revision tags:

   $ kubectl create ns app-ns-1
   $ kubectl label ns app-ns-1 istio.io/rev=prod-stable
   $ kubectl create ns app-ns-2
   $ kubectl label ns app-ns-2 istio.io/rev=prod-stable
   $ kubectl create ns app-ns-3
   $ kubectl label ns app-ns-3 istio.io/rev=prod-canary

4. Bring up a sample curl pod in each namespace:

   $ kubectl apply -n app-ns-1 -f samples/curl/curl.yaml
   $ kubectl apply -n app-ns-2 -f samples/curl/curl.yaml
   $ kubectl apply -n app-ns-3 -f samples/curl/curl.yaml

5. Verify application to control plane mapping using istioctl proxy-status command:

   $ istioctl ps
   NAME                                CLUSTER        CDS        LDS        EDS        RDS        ECDS         ISTIOD                             VERSION
   curl-78ff5975c6-62pzf.app-ns-3      Kubernetes     SYNCED     SYNCED     SYNCED     SYNCED     NOT SENT     istiod-1-28-0-7f6fc6cfd6-s8zfg     1.28.0
   curl-78ff5975c6-8kxpl.app-ns-1      Kubernetes     SYNCED     SYNCED     SYNCED     SYNCED     NOT SENT     istiod-1-27-1-bdf5948d5-n72r2      1.27.1
   curl-78ff5975c6-8q7m6.app-ns-2      Kubernetes     SYNCED     SYNCED     SYNCED     SYNCED     NOT SENT     istiod-1-27-1-bdf5948d5-n72r2      1-27.1

La asignación resultante entre revisiones, etiquetas y namespaces es como se muestra a continuación:

El operador del cluster puede ver esta asignación además de los namespaces etiquetados a través del comando istioctl tag list:

$ istioctl tag list
TAG         REVISION NAMESPACES
default     1-27-1   ...
prod-canary 1-28-0   ...
prod-stable 1-27-1   ...

Después de que el operador del cluster esté satisfecho con la estabilidad del control plane etiquetado con prod-canary, los namespaces etiquetados istio.io/rev=prod-stable se pueden actualizar con una acción modificando la etiqueta de revisión prod-stable para que apunte a la revisión 1-28-0 más nueva.

$ istioctl tag set prod-stable --revision 1-28-0 --overwrite

Ahora, la asignación actualizada entre revisiones, etiquetas y namespaces es como se muestra a continuación:

Reiniciar los workloads inyectadas en los namespaces marcados como prod-stable ahora dará como resultado que esas workloads usen el control plane 1-28-0. Observa que no se requirió ningún reetiquetado de namespace para migrar los workloads a la nueva revisión.

$ kubectl rollout restart deployment -n app-ns-1
$ kubectl rollout restart deployment -n app-ns-2

Verify the application to control plane mapping using istioctl proxy-status command:

$ istioctl ps
NAME                                                   CLUSTER        CDS        LDS        EDS        RDS          ECDS         ISTIOD                             VERSION
curl-5984f48bc7-kmj6x.app-ns-1                         Kubernetes     SYNCED     SYNCED     SYNCED     SYNCED       NOT SENT     istiod-1-28-0-7f6fc6cfd6-jsktb     1.28.0
curl-78ff5975c6-jldk4.app-ns-3                         Kubernetes     SYNCED     SYNCED     SYNCED     SYNCED       NOT SENT     istiod-1-28-0-7f6fc6cfd6-jsktb     1.28.0
curl-7cdd8dccb9-5bq5n.app-ns-2                         Kubernetes     SYNCED     SYNCED     SYNCED     SYNCED       NOT SENT     istiod-1-28-0-7f6fc6cfd6-jsktb     1.28.0

Default tag

La revisión a la que apunta la etiqueta default se considera la revisión predeterminada y tiene un significado semántico adicional. La revisión predeterminada realiza las siguientes funciones:

• Inyecta sidecars para el selector de namespace istio-injection=enabled, el selector de objetos sidecar.istio.io/inject=true y los selectores istio.io/rev=default
• Valida los recursos de Istio
• Roba el bloqueo de líder de las revisiones no predeterminadas y realiza responsabilidades de meshsingleton (como actualizar los estados de los recursos)

Para hacer que una revisión 1-28-0 sea la predeterminada, ejecuta:

$ istioctl tag set default --revision 1-28-0

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 1-27-1:

$ istioctl uninstall --revision 1-27-1 -y

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

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

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 uninstall --revision=canary -y

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.

Cleanup

1. Clean up created revisioned tags:

   $ istioctl tag remove prod-stable
   $ istioctl tag remove prod-canary

2. Clean up the namespaces used for canary upgrade with revision labels example:

   $ kubectl delete ns istio-system test-ns

3. Clean up the namespaces used for canary upgrade with revision tags example:

   $ kubectl delete ns istio-system app-ns-1 app-ns-2 app-ns-3