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Canary-based Migration to Mesh CA

Migrating to Cloud Service Mesh certificate authority (Mesh CA) from Istio CA (also known as Citadel) requires migrating the root of trust. Prior to Cloud Service Mesh 1.10, if you wanted to migrate from Istio on Google Kubernetes Engine (GKE) to Cloud Service Mesh with Mesh CA, you needed to schedule downtime because Cloud Service Mesh was not able to load multiple root certificates. Therefore, during the migration, the newly deployed workloads trust the new root certificate, while others trust the old root certificate. Workloads using certificates signed by different root certificates can't authenticate with each other. This means that mutual TLS (mTLS) traffic is interrupted during the migration. The entire cluster only fully recovers when the control plane and all workloads in all namespaces are redeployed with Mesh CA's certificate. If your mesh has multiple clusters with workloads that send requests to workloads on another cluster, all workloads on those clusters need to be updated as well.

Use the steps in this guide for the following use cases:

Migrate from Istio on GKE to the Cloud Service Mesh 1.23.4-asm.1 in-cluster control plane with Mesh CA.
Upgrade from Cloud Service Mesh 1.15 or a 1.16 patch release with Istio CA to the Cloud Service Mesh 1.23.4-asm.1 in-cluster control plane with Mesh CA.

Limitations

All GKE clusters must be in the same Google Cloud project.

Prerequisites

Follow the steps in Install dependent tools and validate cluster to:

Required tools

During the migration, you run a Google-provided tool, migrate_ca, to validate the following for each Pod in the cluster:

The root certificate for Istio CA and Mesh CA.
The workload mTLS certificate issued by Istio CA and by Mesh CA.
The trust domains configured by Istio CA and Mesh CA.

This tool has the following dependencies:

awk
grep
istioctl Running the asmcli install downloads the version of istioctl that matches the version of Cloud Service Mesh that you are installing.
jq
kubectl
openssl

Overview of the migration

To migrate to Mesh CA, you follow the revision-based migration process (also referred to as a "canary upgrade"). With a revision-based migration, a new control plane revision is deployed alongside the existing control plane. You then gradually move your workloads to the new revision, which lets you monitor the effect of the migration through the process. During the migration process, authentication and authorization are fully functional between workloads using the Mesh CA and workloads using the Istio CA.

The following is an outline of the migration to Mesh CA:

Distribute the Mesh CA root of trust.
1. Install a new control plane revision that uses the Istio CA with an option that will distribute the Mesh CA root of trust.
2. Migrate workloads to the new control plane, namespace by namespace, and test your application. When all workloads are successfully migrated to the new control plane, remove the old control plane.
Migrate to Mesh CA. Now that all sidecar proxies are configured with the old root of trust and the Mesh CA root of trust, you can migrate to Mesh CA without downtime. Again, you follow the revision-based migration process:
1. Install a control plane revision with Mesh CA enabled.
2. Migrate workloads to the new control plane revision, namespace by namespace, and test your application. When all workloads are successfully migrated to the new control plane, remove the old control plane.
3. Remove CA secrets in the cluster that are associated with the old CA and restart the new control plane.

Distribute the Mesh CA root of trust

Before you can migrate to Mesh CA, all GKE clusters in the mesh must have Cloud Service Mesh 1.10 or later, and all clusters must be configured with a control plane option that triggers the root of trust for Mesh CA to be distributed to the proxies of all workloads on the cluster. When the process is finished, each proxy is configured with both the old and the new root of trusts. With this scheme, when you migrate to Mesh CA, workloads using Mesh CA will be able to authenticate with workloads using the old CA.

Install a new control plane revision

Install a control plane revision with an option that distributes the Mesh CA root of trust.

Follow the steps in Install dependent tools and validate cluster to get ready to use a Google-provided tool, asmcli, to install the new control plane revision.
Make sure you have the version of asmcli that installs Cloud Service Mesh 1.11 or higher:
```
./asmcli --version
```

Run asmcli install. In the following command, replace the placeholders with your values.

 ./asmcli install \
   --fleet_id FLEET_PROJECT_ID \
   --kubeconfig KUBECONFIG_FILE \
   --enable_all \
   --ca citadel \
   --ca_cert CA_CERT_FILE_PATH \
   --ca_key CA_KEY_FILE_PATH \
   --root_cert ROOT_CERT_FILE_PATH \
   --cert_chain CERT_CHAIN_FILE_PATH \
   --option ca-migration-citadel \
   --revision_name REVISION_1 \
   --output_dir DIR_PATH

--fleet_id The project ID of the fleet host project.
--kubeconfig The path to the kubeconfig file You can specify either a relative path or a full path. The environment variable $PWD doesn't work here.
--output_dir Include this option to specify a directory where asmcli downloads the anthos-service-mesh package and extracts the installation file, which contains, istioctl, samples, and manifests. Otherwise asmcli downloads the files to a tmp directory. You can specify either a relative path or a full path. The environment variable $PWD doesn't work here.
--enable_all Allows the tool to:
- Grant required IAM permissions.
- Enable the required Google APIs.
- Set a label on the cluster that identifies the mesh.
- Register the cluster to the fleet if it isn't already registered.
-ca citadel To avoid downtime, specify Istio CA (the citadel option corresponds to Istio CA). Don't switch to Mesh CA at this point.
--ca_cert The intermediate certificate.
--ca_key The key for the intermediate certificate
--root_cert The root certificate.
--cert_chain The certificate chain.
--option ca-migration-citadel When you redeploy your workloads, this option triggers the new root of trust to be distributed to the sidecar proxies of the workloads.
REVISION_1: Recommended. A revision label is a key-value pair that is set on the control plane. The revision label key is always istio.io/rev. By default, the tool sets the value for the revision label based on the Cloud Service Mesh version, for example: asm-1234-1. We recommend that you include this option and replace REVISION_1 with a name that describes the installation, such as asm-1234-1-distribute-root. The name must be a DNS-1035 label, and it must consist of lower case alphanumeric characters or -, start with an alphabetic character, and end with an alphanumeric character (such as my-name or abc-123).

Migrate workloads to the new control plane

To finish distributing the new root of trust, you need to label your namespaces with the revision label istio.io/rev=<var>REVISION_1</var>-distribute-root and restart your workloads. When testing your workloads after restarting them, you run a tool to validate that the sidecar proxy is configured with both the old and new root of trust for Mesh CA.

Set the current context for kubectl. In the following command, change --region to --zone if you have a single-zone cluster.

gcloud container clusters get-credentials CLUSTER_NAME \
    --project=PROJECT_ID \
    --region=CLUSTER_LOCATION

Download the validation tool:

curl https://raw.githubusercontent.com/GoogleCloudPlatform/anthos-service-mesh-packages/master/scripts/ca-migration/migrate_ca > migrate_ca

Set the executable bit on the tool:
```
chmod +x migrate_ca
```
The migrate_ca tool calls istioctl, which is version dependent. The asmcli tool adds a symlink to istioctl in the directory you specified for --output_dir. Make sure that directory is at the beginning of your path. In the following command, replace ISTIOCTL_PATH with the directory that contains istioctl that the tool downloaded.
```
export PATH=ISTIOCTL_PATH:$PATH
which istioctl
echo $PATH
```

Get the revision label that is on istiod and the istio-ingressgateway.

kubectl get pod -n istio-system -L istio.io/rev

The output is similar to the following:

NAME                                                             READY   STATUS    RESTARTS   AGE   REV
istio-ingressgateway-5fd454f8ff-t7w9x                            1/1     Running   0          36m   default
istio-ingressgateway-asm-195-2-distribute-root-c6ccfbdbd-z2s9p   1/1     Running   0          18m   asm-195-2-distribute-root
istio-ingressgateway-asm-195-2-distribute-root-c6ccfbdbd-zr2cs   1/1     Running   0          18m   asm-195-2-distribute-root
istiod-68bc495f77-shl2h                                          1/1     Running   0          36m   default
istiod-asm-195-2-distribute-root-6f764dbb7c-g9f8c                1/1     Running   0          18m   asm-195-2-distribute-root
istiod-asm-195-2-distribute-root-6f764dbb7c-z7z9s                1/1     Running   0          18m   asm-195-2-distribute-root

In the output, under the REV column, note the value of the revision label for the new revision, which matches the revision label that you specified when you ran asmcli install. In this example, the value is asm-1234-1-distribute-root.
You need to delete the old revision of istiod when you finish moving workloads to the new revision. Note the value in the revision label for the old istiod revision. The example output shows a migration from Istio, which is using the default revision.

Add the revision label to a namespace and remove the istio-injection label (if it exists). In the following command, replace NAMESPACE with the namespace to label.
```
kubectl label namespace NAMESPACE istio.io/rev=REVISION_1 istio-injection- --overwrite
```
If you see "istio-injection not found" in the output, you can ignore it. That means that the namespace didn't previously have the istio-injection label. Because auto-injection behavior is undefined when a namespace has both the istio-injection and the revision label, all kubectl label commands in the Cloud Service Mesh documentation explicitly ensure that only one is set.

Restart the Pods to trigger re-injection.

kubectl rollout restart deployment -n NAMESPACE

Test your application to verify that the workloads are working correctly.
If you have workloads in other namespaces, repeat the steps to label the namespace and restart Pods.

Validate that the sidecar proxies for all workloads on the cluster are configured with both the old and new root certificates:

./migrate_ca check-root-cert

Expected output:

Namespace: foo
httpbin-66cdbdb6c5-pmzps.foo trusts [CITADEL MESHCA]
sleep-64d7d56698-6tmjm.foo trusts [CITADEL MESHCA]

If you need to migrate gateways, follow the steps in Canary Upgrades (advanced) to install new gateway deployments. Keep the following points in mind:
- Use REVISION_1 as the revision label.
- Deploy the gateway resources in the same namespace as the gateway from the older installation to perform zero-downtime migration. Ensure that the service resources pointing to the older gateway should include the newer deployments now as well.
- Do not delete the older gateway deployments until you are sure your application is working properly (after the next step).
If you are satisfied that your application is working as expected, continue with the steps to transition to the new version of istiod. If there's an issue with your application, follow the steps to rollback.
Complete the transition
If you are satisfied that your application is working as expected, remove the old control plane to complete the transition to the new version.
1. Change to the directory where the files from the anthos-service-mesh GitHub repository are located.
2. Configure the validating webhook to use the new control plane.
  kubectl apply -f asm/istio/istiod-service.yaml
3. Delete the old istio-ingressgatewayDeployment. The command that you run depends on whether you are migrating from Istio or upgrading from a previous version of Cloud Service Mesh:
  Migrate
  If you migrated from Istio, the old istio-ingressgateway doesn't have a revision label.
  
  kubectl delete deploy/istio-ingressgateway -n istio-system
  
  Upgrade
  If you upgraded from a previous Cloud Service Mesh version, in the following command, replace OLD_REVISION with the revision label for the previous version of the istio-ingressgateway.
  
  kubectl delete deploy -l app=istio-ingressgateway,istio.io/rev=OLD_REVISION -n istio-system --ignore-not-found=true
4. Delete the old revision of istiod. The command that you use depends on whether you are migrating from Istio or upgrading from a previous version of Cloud Service Mesh.
  Migrate
  If you migrated from Istio, the old istio-ingressgateway doesn't have a revision label.
  
  kubectl delete Service,Deployment,HorizontalPodAutoscaler,PodDisruptionBudget istiod -n istio-system --ignore-not-found=true
  
  Upgrade
  If you upgraded from a previous Cloud Service Mesh version, in the following command, make sure that OLD_REVISION matches the revision label for the previous version of istiod.
  
  kubectl delete Service,Deployment,HorizontalPodAutoscaler,PodDisruptionBudget istiod-OLD_REVISION -n istio-system --ignore-not-found=true
5. Remove the old version of the IstioOperator configuration.
  kubectl delete IstioOperator installed-state-OLD_REVISION -n istio-system
  The expected output is similar to the following:
  istiooperator.install.istio.io "installed-state-OLD_REVISION" deleted
Rollback
If you encountered an issue when testing your application with the new version of istiod, follow these steps to rollback to the previous version:
1. Delete the new gateway deployments installed as part of step 11.
2. Relabel your namespace to enable auto-injection with the previous version of istiod. The command that you use depends on whether you used a revision label or istio-injection=enabled with the previous version.
  - If you used a revision label for auto-injection:
    
    kubectl label namespace NAMESPACE istio.io/rev=OLD_REVISION --overwrite
  - If you used istio-injection=enabled:
    
    kubectl label namespace NAMESPACE istio.io/rev- istio-injection=enabled --overwrite
  Expected output:
  namespace/NAMESPACE labeled
3. Confirm that the revision label on the namespace matches the revision label on the previous version of istiod:
  kubectl get ns NAMESPACE --show-labels
4. Restart the Pods to trigger re-injection so the proxies have the previous version:
  kubectl rollout restart deployment -n NAMESPACE
5. Remove the new istio-ingressgateway Deployment.
  kubectl delete deploy -l app=istio-ingressgateway,istio.io/rev=REVISION_1 -n istio-system --ignore-not-found=true
6. Remove the new revision of istiod.
  kubectl delete Service,Deployment,HorizontalPodAutoscaler,PodDisruptionBudget istiod-REVISION_1 -n istio-system --ignore-not-found=true
7. Remove the new IstioOperator configuration.
  kubectl delete IstioOperator installed-state-asm-1234-1-distribute-root -n istio-system
  Expected output is similar to the following:
  istiooperator.install.istio.io "installed-state-asm-1234-1-distribute-root" deleted

Migrate to Mesh CA

Now that the sidecar proxies for all workloads are configured with both the old root of trust and the new root of trust for Mesh CA, the steps to migrate to Mesh CA are similar to those that you did to distribute the Mesh CA root of trust:

Install a new control plane with Mesh CA enabled

You use asmcli install to install a new control plane revision that has Mesh CA enabled.

If you customized the previous installation, you need to specify the same overlay files when you run asmcli install.
Run asmcli install. In the following command, replace the placeholders with your values.
```
 ./asmcli install \
   --fleet_id FLEET_PROJECT_ID \
   --kubeconfig KUBECONFIG_FILE \
   --output_dir DIR_PATH \
   --enable_all \
   --ca mesh_ca \
   --root_cert ROOT_CERT_FILE_PATH \
   --cert_chain CERT_CHAIN_FILE_PATH
   --option ca-migration-meshca \
  --revision_name REVISION_2 \
  --output_dir DIR_PATH \
  OVERLAYS
```

Migrate workloads to the new control plane

To finish the installation, you need to label your namespaces with the new revision label and restart your workloads.

Get the revision label that is on istiod and the istio-ingressgateway.

kubectl get pod -n istio-system -L istio.io/rev

The output is similar to the following:

NAME                                                                          READY   STATUS    RESTARTS   AGE   REV
istio-ingressgateway-asm-1234-1-distribute-root-65d884685d-6hrdk      1/1     Running   0          67m   asm-1234-1-distribute-root
istio-ingressgateway-asm-1234-1-distribute-root65d884685d-94wgz       1/1     Running   0          67m   asm-1234-1-distribute-root
istio-ingressgateway-asm-1234-1-meshca-ca-migration-8b5fc8767-gk6hb   1/1     Running   0          5s    asm-1234-1-meshca-ca-migration
istio-ingressgateway-asm-1234-1-meshca-ca-migration-8b5fc8767-hn4w2   1/1     Running   0          20s   asm-1234-1-meshca-ca-migration
istiod-asm-1234-1-distribute-root-67998f4b55-lrzpz                    1/1     Running   0          68m   asm-1234-1-distribute-root
istiod-asm-1234-1-distribute-root-67998f4b55-r76kr                    1/1     Running   0          68m   asm-1234-1-distribute-root
istiod-asm-1234-1-meshca-ca-migration-5cd96f88f6-n7tj9                1/1     Running   0          27s   asm-1234-1-meshca-ca-migration
istiod-asm-1234-1-meshca-ca-migration-5cd96f88f6-wm68b                1/1     Running   0          27s   asm-1234-1-meshca-ca-migration

In the output, under the REV column, note the value of the revision label for the new version. In this example, the value is asm-1234-1-meshca-ca-migration.
Also note the value in the revision label for the old istiod version. You need this to delete the old version of istiod when you finish moving workloads to the new version. In the example, the value of the revision label for the previous revision is asm-1234-1-distribute-root.

Add the new revision label to a namespace In the following command, replace NAMESPACE with the namespace to label.
```
kubectl label namespace NAMESPACE istio.io/rev=REVISION_2 --overwrite
```

Restart the Pods to trigger re-injection.

kubectl rollout restart deployment -n NAMESPACE

Test your application to verify that the workloads are working correctly. Make sure that mTLS communication works between workloads in the older namespace and workloads in the newer namespace.
If you have workloads in other namespaces, repeat the steps to label the namespace and restart Pods.
Follow the steps outlined in In-place upgrades to upgrade the older gateway deployments installed in step 11 of the previous section to the latest revision REVISION_2.
If you are satisfied that your application is working as expected, continue with the steps to transition to the new control plane. If there's an issue with your application, follow the steps to rollback.
Complete the transition
If you are satisfied that your application is working as expected, remove the old control plane to complete the transition to the new version.
1. Change to the directory where the files from the anthos-service-mesh GitHub repository are located.
2. Configure the validating webhook to use the new control plane.
  kubectl apply -f asm/istio/istiod-service.yaml
3. Delete the old istio-ingressgatewayDeployment. In the following command, replace OLD_REVISION with the revision label for the previous version of the istio-ingressgateway.
  kubectl delete deploy -l app=istio-ingressgateway,istio.io/rev=OLD_REVISION -n istio-system --ignore-not-found=true
4. Delete the old istiod revision. In the following command, replace OLD_REVISION with the revision label for the previous version of istiod.
  kubectl delete Service,Deployment,HorizontalPodAutoscaler,PodDisruptionBudget istiod-OLD_REVISION -n istio-system --ignore-not-found=true
5. Remove the old IstioOperator configuration.
  kubectl delete IstioOperator installed-state-OLD_REVISION -n istio-system
  The expected output is similar to the following:
  istiooperator.install.istio.io "installed-state-OLD_REVISION" deleted
Rollback
If you encountered an issue when testing your application with the new istiod revision, follow these steps to rollback to the previous revision:
1. Follow the steps in In-place upgrades to downgrade the gateway deployments previously upgraded in step 6 of this section to the older revision REVISION_1.
2. Relabel your namespace to enable auto-injection with the previous istiod revision.
  kubectl label namespace NAMESPACE istio.io/rev=OLD_REVISION --overwrite
  Expected output:
  namespace/NAMESPACE labeled
3. Confirm that the revision label on the namespace matches the revision label on the previous version of istiod:
  kubectl get ns NAMESPACE --show-labels
4. Restart the Pods to trigger re-injection so the proxies have the previous version:
  kubectl rollout restart deployment -n NAMESPACE
5. Remove the new istio-ingressgateway Deployment.
  kubectl delete deploy -l app=istio-ingressgateway,istio.io/rev=REVISION_2 -n istio-system --ignore-not-found=true
6. Remove the new version of istiod. Make sure that the revision label in the following command matches your revision.
  kubectl delete Service,Deployment,HorizontalPodAutoscaler,PodDisruptionBudget istiod-REVISION_2 -n istio-system --ignore-not-found=true
7. Remove the new version of the IstioOperator configuration.
  kubectl delete IstioOperator installed-state-REVISION_2 -n istio-system
  Expected output is similar to the following:
  istiooperator.install.istio.io "installed-state-REVISION_2" deleted

Remove the CA secrets and restart the new control plane

Preserve secrets just in case you need them:

kubectl get secret/cacerts -n istio-system -o yaml > save_file_1
kubectl get secret/istio-ca-secret -n istio-system -o yaml > save_file_2

Remove the CA secrets in the cluster associated with the old CA:

kubectl delete secret cacerts istio-ca-secret -n istio-system --ignore-not-found

Restart the newly installed control plane. This makes sure the old root of trust is cleaned up from all workloads running in the mesh.
```
kubectl rollout restart deployment -n istio-system
```

Canary-based Migration to Mesh CA

Limitations

Prerequisites

Required tools

Overview of the migration

Distribute the Mesh CA root of trust

Install a new control plane revision

Migrate workloads to the new control plane

Complete the transition

Migrate

Upgrade

Migrate

Upgrade

Rollback

Migrate to Mesh CA

Install a new control plane with Mesh CA enabled

Migrate workloads to the new control plane

Complete the transition

Rollback

Remove the CA secrets and restart the new control plane