Upgrading a multi-cluster GKE environment with Multi Cluster Ingress

Last reviewed 2022-12-15 UTC

Autopilot Standard

This tutorial shows how to upgrade a multi-cluster Google Kubernetes Engine (GKE) environment using Multi Cluster Ingress . This tutorial is a continuation of the multi-cluster GKE upgrades using Multi Cluster Ingress document that explains the process, architecture, and terms in more detail. We recommend that you read the concept document before this tutorial.

For a detailed comparison between Multi Cluster Ingress (MCI), Multi-cluster Gateway (MCG), and load balancer with Standalone Network Endpoint Groups (LB and Standalone NEGs), see Choose your multi-cluster load balancing API for GKE.

This document is intended for Google Cloud administrators who are responsible for maintaining fleets for GKE clusters.

We recommend auto-upgrading your GKE clusters. Auto-upgrade is a fully managed way of getting your clusters (control plane and nodes) automatically updated on a release schedule that is determined by Google Cloud. This requires no intervention from the operator. However, if you want more control over how and when clusters are upgraded, this tutorial walks through a method of upgrading multiple clusters where your apps run on all clusters. It then uses Multi Cluster Ingress to drain one cluster at a time before upgrading.

Architecture

This tutorial uses the following architecture. There are a total of three clusters: two clusters (blue and green) act as identical clusters with the same app deployed and one cluster (ingress-config) acts as the control plane cluster that configures Multi Cluster Ingress. In this tutorial, you deploy a sample app to two app clusters (blue and green clusters).

Architecture of two identical clusters and one control plane cluster.

Objectives

Create three GKE clusters and register them as a fleet.
Configure one GKE cluster (ingress-config) as the central configuration cluster.
Deploy a sample app to the other GKE clusters.
Configure Multi Cluster Ingress to send client traffic to the app that is running on both app clusters.
Set up a load generator to the app and configure monitoring.
Remove (drain) one app cluster from the multi-cluster Ingress and upgrade the drained cluster.
Spill traffic back to the upgraded cluster using Multi Cluster Ingress.

Costs

In this document, you use the following billable components of Google Cloud:

To generate a cost estimate based on your projected usage, use the pricing calculator.

New Google Cloud users might be eligible for a free trial.

When you finish the tasks that are described in this document, you can avoid continued billing by deleting the resources that you created. For more information, see Clean up.

Before you begin

This tutorial requires you to Set up Multi Cluster Ingress so that the following is set up:
- Two or more clusters with the same apps, such as namespaces, Deployments, and Services, running on all clusters.
- Autoupgrade is turned off for all clusters.
- Clusters are VPC-native clusters that use alias IP address ranges
- Have HTTP load balancing enabled (enabled by default).
- gcloud --version must be 369 or higher. GKE cluster registration steps depend on this version or higher.
In the Google Cloud console, on the project selector page, select or create a Google Cloud project.
Roles required to select or create a project
- Select a project: Selecting a project doesn't require a specific IAM role—you can select any project that you've been granted a role on.
- Create a project: To create a project, you need the Project Creator (roles/resourcemanager.projectCreator), which contains the resourcemanager.projects.create permission. Learn how to grant roles.
Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

Go to project selector
Verify that billing is enabled for your Google Cloud project.
In the Google Cloud console, activate Cloud Shell.

Activate Cloud Shell

Set your default project:

export PROJECT=$(gcloud info --format='value(config.project)')
gcloud config set project ${PROJECT}

Enable the GKE, Hub, and multiclusteringress APIs:

gcloud services enable container.googleapis.com \
                       gkehub.googleapis.com \
                       multiclusteringress.googleapis.com \
                       multiclusterservicediscovery.googleapis.com

Set up the environment

In Cloud Shell, clone the repository to get the files for this tutorial:

cd ${HOME}
git clone https://github.com/GoogleCloudPlatform/kubernetes-engine-samples

Create a WORKDIR directory:

cd kubernetes-engine-samples/networking/gke-multicluster-upgrade-mci/
export WORKDIR=`pwd`

Create and register GKE clusters to Hub

In this section, you create three GKE clusters and register them to GKE Hub.

Create GKE clusters

In Cloud Shell, create three GKE clusters:

gcloud container clusters create ingress-config --location us-west1-a \
--release-channel=None --no-enable-autoupgrade --num-nodes=4 \
--enable-ip-alias --workload-pool=${PROJECT}.svc.id.goog --quiet --async
gcloud container clusters create blue --location us-west1-b --num-nodes=3 \
--release-channel=None --no-enable-autoupgrade --enable-ip-alias \
--workload-pool=${PROJECT}.svc.id.goog --quiet --async
gcloud container clusters create green --location us-west1-c --num-nodes=3 \
--release-channel=None --no-enable-autoupgrade --enable-ip-alias \
--workload-pool=${PROJECT}.svc.id.goog --quiet

For the purpose of this tutorial, you create the clusters in a single region, in three different zones: us-west1-a,us-west1-b, and us-west1-c. For more information about regions and zones, see Geography and regions.

Wait a few minutes until all clusters are successfully created. Ensure that the clusters are running:

gcloud container clusters list

The output is similar to the following:

NAME: ingress-config
LOCATION: us-west1-a
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 35.233.186.135
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 4
STATUS: RUNNING

NAME: blue
LOCATION: us-west1-b
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 34.82.35.222
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 3
STATUS: RUNNING

NAME: green
LOCATION: us-west1-c
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 35.185.204.26
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 3
STATUS: RUNNING

Create a kubeconfig file and connect to all clusters to generate entries in the kubeconfig file:

touch gke-upgrade-kubeconfig
export KUBECONFIG=gke-upgrade-kubeconfig
gcloud container clusters get-credentials ingress-config \
    --location us-west1-a --project ${PROJECT}
gcloud container clusters get-credentials blue --location us-west1-b \
    --project ${PROJECT}
gcloud container clusters get-credentials green --location us-west1-c \
    --project ${PROJECT}

You use the kubeconfig file to create authentication to clusters by creating a user and context for each cluster. After you create the kubeconfig file, you can quickly switch context between clusters.

Verify that you have three clusters in the kubeconfig file:

kubectl config view -ojson | jq -r '.clusters[].name'

The output is the following:

gke_gke-multicluster-upgrades_us-west1-a_ingress-config
gke_gke-multicluster-upgrades_us-west1-b_blue
gke_gke-multicluster-upgrades_us-west1-c_green

Get the context for the three clusters for later use:

export INGRESS_CONFIG_CLUSTER=$(kubectl config view -ojson | jq \
    -r '.clusters[].name' | grep ingress-config)
export BLUE_CLUSTER=$(kubectl config view -ojson | jq \
    -r '.clusters[].name' | grep blue)
export GREEN_CLUSTER=$(kubectl config view -ojson | jq \
    -r '.clusters[].name' | grep green)
echo -e "${INGRESS_CONFIG_CLUSTER}\n${BLUE_CLUSTER}\n${GREEN_CLUSTER}"

The output is the following:

gke_gke-multicluster-upgrades_us-west1-a_ingress-config
gke_gke-multicluster-upgrades_us-west1-b_blue
gke_gke-multicluster-upgrades_us-west1-c_green

Register GKE clusters to a fleet

Registering your clusters to a fleet lets you operate your Kubernetes clusters across hybrid environments. Clusters registered to fleets can use advanced GKE features such as Multi Cluster Ingress. To register a GKE cluster to a fleet, you can use a Google Cloud service account directly, or use the recommended Workload Identity Federation for GKE approach, which allows a Kubernetes service account in your GKE cluster to act as an Identity and Access Management service account.

gcloud container fleet memberships register ingress-config \
    --gke-cluster=us-west1-a/ingress-config \
    --enable-workload-identity

gcloud container fleet memberships register blue \
    --gke-cluster=us-west1-b/blue \
    --enable-workload-identity

gcloud container fleet memberships register green \
    --gke-cluster=us-west1-c/green \
    --enable-workload-identity

Verify that the clusters are registered:

gcloud container fleet memberships list

The output is similar to the following:

NAME: blue
EXTERNAL_ID: 401b4f08-8246-4f97-a6d8-cf1b78c2a91d

NAME: green
EXTERNAL_ID: 8041c36a-9d42-40c8-a67f-54fcfd84956e

NAME: ingress-config
EXTERNAL_ID: 65ac48fe-5043-42db-8b1e-944754a0d725

Configure the ingress-config cluster as the configuration cluster for Multi Cluster Ingress by enabling the multiclusteringress feature through the Hub:
```
gcloud container fleet ingress enable --config-membership=ingress-config
```
The preceding command adds the MulticlusterIngress and MulticlusterService CRDs (Custom Resource Definitions) to the ingress-config cluster. This command takes a few minutes to complete. Wait before proceeding to the next step.

Verify that the ingress-cluster cluster was successfully configured for Multi Cluster Ingress:

watch gcloud container fleet ingress describe

Wait until the output is similar to the following:

createTime: '2022-07-05T10:21:40.383536315Z'
membershipStates:
  projects/662189189487/locations/global/memberships/blue:
    state:
      code: OK
      updateTime: '2022-07-08T10:59:44.230329189Z'
  projects/662189189487/locations/global/memberships/green:
    state:
      code: OK
      updateTime: '2022-07-08T10:59:44.230329950Z'
  projects/662189189487/locations/global/memberships/ingress-config:
    state:
      code: OK
      updateTime: '2022-07-08T10:59:44.230328520Z'
name: projects/gke-multicluster-upgrades/locations/global/features/multiclusteringress
resourceState:
  state: ACTIVE
spec:
  multiclusteringress:
    configMembership: projects/gke-multicluster-upgrades/locations/global/memberships/ingress-config
state:
  state:
    code: OK
    description: Ready to use
    updateTime: '2022-07-08T10:57:33.303543609Z'
updateTime: '2022-07-08T10:59:45.247576318Z'

To exit the watch command, press Control+C.

Deploy a sample application to the blue and green clusters

In Cloud Shell, deploy the sample whereami app to the blue and green clusters:

kubectl --context ${BLUE_CLUSTER} apply -f ${WORKDIR}/application-manifests
kubectl --context ${GREEN_CLUSTER} apply -f ${WORKDIR}/application-manifests

Wait a few minutes and ensure that all Pods in the blue and green clusters have a Running status:

kubectl --context ${BLUE_CLUSTER} get pods
kubectl --context ${GREEN_CLUSTER} get pods

The output is similar to the following:

NAME                                   READY   STATUS    RESTARTS   AGE
whereami-deployment-756c7dc74c-zsmr6   1/1     Running   0          74s
NAME                                   READY   STATUS    RESTARTS   AGE
whereami-deployment-756c7dc74c-sndz7   1/1     Running   0          68s.

Configure multi-cluster Ingress

In this section, you create a multi-cluster Ingress that sends traffic to the application running on both blue and green clusters. You use Cloud Load Balancing to create a load balancer that uses the whereami app in both the blue and green clusters as backends. To create the load balancer, you need two resources: a MultiClusterIngress and one or more MultiClusterServices. MultiClusterIngress and MultiClusterService objects are multi-cluster analogs for the existing Kubernetes Ingress and Service resources used in the single cluster context.

In Cloud Shell, deploy the MulticlusterIngress resource to the ingress-config cluster:

kubectl --context ${INGRESS_CONFIG_CLUSTER} apply -f ${WORKDIR}/multicluster-manifests/mci.yaml

The output is the following:

multiclusteringress.networking.gke.io/whereami-mci created

Deploy the MulticlusterService resource to the ingress-config cluster:

kubectl --context ${INGRESS_CONFIG_CLUSTER} apply -f ${WORKDIR}/multicluster-manifests/mcs-blue-green.yaml

The output is the following:

multiclusterservice.networking.gke.io/whereami-mcs created

To compare the two resources, do the following:
- Inspect the MulticlusterIngress resource:
```
kubectl --context ${INGRESS_CONFIG_CLUSTER} get multiclusteringress -o yaml
```
  The output contains the following:
```
spec:
  template:
    spec:
      backend:
        serviceName: whereami-mcs
        servicePort: 8080
```
  The MulticlusterIngress resource is similar to the Kubernetes Ingress resource except that the serviceName specification points to a MulticlusterService resource.
- Inspect the MulticlusterService resource:
```
kubectl --context ${INGRESS_CONFIG_CLUSTER} get multiclusterservice -o yaml
```
  The output contains the following:
```
spec:
  clusters:
  - link: us-west1-b/blue
  - link: us-west1-c/green
  template:
    spec:
      ports:
      - name: web
        port: 8080
        protocol: TCP
        targetPort: 8080
      selector:
        app: whereami
```
  The MulticlusterService resource is similar to a Kubernetes Service resource, except it has a clusters specification. The clusters value is the list of registered clusters where the MulticlusterService resource is created.
- Verify that the MulticlusterIngress resource created a load balancer with a backend service pointing to the MulticlusterServiceresource:
```
watch kubectl --context ${INGRESS_CONFIG_CLUSTER} \
      get multiclusteringress -o jsonpath="{.items[].status.VIP}"
```
  This may take up to 10 minutes. Wait until the output is similar to the following:
```
34.107.246.9
```
  To exit the watch command, press Control+C.

In Cloud Shell, get the Cloud Load Balancing VIP:

export GCLB_VIP=$(kubectl --context ${INGRESS_CONFIG_CLUSTER} \
       get multiclusteringress -o json | jq -r '.items[].status.VIP') \
       && echo ${GCLB_VIP}

The output is similar to the following:

34.107.246.9

Use curl to access the load balancer and the deployed application:

curl ${GCLB_VIP}

The output is similar to the following:

{
  "cluster_name": "green",
  "host_header": "34.107.246.9",
  "pod_name": "whereami-deployment-756c7dc74c-sndz7",
  "pod_name_emoji": "😇",
  "project_id": "gke-multicluster-upgrades",
  "timestamp": "2022-07-08T14:26:07",
  "zone": "us-west1-c"
}

Run the curl command repeatedly. Notice that the requests are being load balanced between the whereami application that is deployed to two clusters, blue and green.

Set up the load generator

In this section, you set up a loadgenerator Service that generates client traffic to the Cloud Load Balancing VIP. First, traffic is sent to the blue and green clusters because the MulticlusterService resource is set up to send traffic to both clusters. Later, you configure the MulticlusterService resource to send traffic to a single cluster.

Configure the loadgenerator manifest to send client traffic to the Cloud Load Balancing:

TEMPLATE=loadgen-manifests/loadgenerator.yaml.templ && envsubst < ${TEMPLATE} > ${TEMPLATE%.*}

Deploy the loadgenerator in the ingress-config cluster:

kubectl --context ${INGRESS_CONFIG_CLUSTER} apply -f ${WORKDIR}/loadgen-manifests

Verify that the loadgenerator Pods in the ingress-config cluster all have a status of Running:

kubectl --context ${INGRESS_CONFIG_CLUSTER} get pods

The output is similar to the following:

NAME                             READY   STATUS    RESTARTS   AGE
loadgenerator-5498cbcb86-hqscp   1/1     Running   0          53s
loadgenerator-5498cbcb86-m2z2z   1/1     Running   0          53s
loadgenerator-5498cbcb86-p56qb   1/1     Running   0          53s

If any of the Pods don't have a status of Running, wait a few minutes and then run the command again.

Monitor traffic

In this section, you monitor the traffic to the whereami app using the Google Cloud console.

In the previous section, you set up a loadgenerator deployment that simulates client traffic by accessing the whereami app through the Cloud Load Balancing VIP. You can monitor these metrics through the Google Cloud console. You set up monitoring first so that you can monitor as you drain clusters for upgrades (described in the next section).

Create a dashboard to show the traffic reaching Multi Cluster Ingress:

export DASH_ID=$(gcloud monitoring dashboards create \
    --config-from-file=dashboards/cloud-ops-dashboard.json \
    --format=json | jq  -r ".name" | awk -F '/' '{print $4}')

The output is similar to the following:

Created [721b6c83-8f9b-409b-a009-9fdf3afb82f8]

Metrics from Cloud Load Balancing are available in the Google Cloud console. Generate the URL:

echo "https://console.cloud.google.com/monitoring/dashboards/builder/${DASH_ID}/?project=${PROJECT}&timeDomain=1h"

The output is similar to the following:

https://console.cloud.google.com/monitoring/dashboards/builder/721b6c83-8f9b-409b-a009-9fdf3afb82f8/?project=gke-multicluster-upgrades&timeDomain=1h"

In a browser, go to the URL generated by the preceding command.

The traffic to the sample application is going from the load generator to both blue and green clusters (noted by the two zones the clusters are in). The timeline metrics chart shows traffic going to both backends.The k8s1- mouseover values indicate that the network endpoint group (NEGs) for the two frontend MulticlusterServices are running in the blue and green clusters.

Note: The chart colors may not correspond to the blue and green clusters. It may take several minutes for traffic to become visible in the chart.

Drain and upgrade the `blue` cluster

In this section, you drain the blue cluster. Draining a cluster means that you remove it from the load balancing pool. After you drain the blue cluster, all client traffic destined for the application goes to the green cluster. You can monitor this process as described in the previous section. After the cluster is drained, you can upgrade the drained cluster. After the upgrade, you can put it back in the load balancing pool. You repeat these steps to upgrade the other cluster (not shown in this tutorial).

To drain the blue cluster, you update the MulticlusterService resource in the ingress-cluster cluster and remove the blue cluster from the clusters specification.

Drain the blue cluster

In Cloud Shell, update the MulticlusterService resource in the ingress-config cluster:

kubectl --context ${INGRESS_CONFIG_CLUSTER} \
          apply -f ${WORKDIR}/multicluster-manifests/mcs-green.yaml

Verify that you only have the green cluster in the clusters specification:
```
kubectl --context ${INGRESS_CONFIG_CLUSTER} get multiclusterservice \
        -o json | jq '.items[].spec.clusters'
```
The output is the following:
```
[
  {
    "link": "us-west1-c/green"
  }
]
```
Only the green cluster is listed in the clusters specification so only the green cluster is in the load balancing pool.

You can see metrics from the Cloud Load Balancing metrics in the Google Cloud console. Generate the URL:

echo "https://console.cloud.google.com/monitoring/dashboards/builder/${DASH_ID}/?project=${PROJECT}&timeDomain=1h"

In a browser, go to the URL generated from the previous command.

The chart shows that only the green cluster is receiving traffic.

Upgrade the `blue` cluster

Now that the blue cluster is no longer receiving any client traffic, you can upgrade the cluster (control plane and nodes).

In Cloud Shell, get the current version of the clusters:

gcloud container clusters list

The output is similar to the following:

NAME: ingress-config
LOCATION: us-west1-a
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 35.233.186.135
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 4
STATUS: RUNNING

NAME: blue
LOCATION: us-west1-b
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 34.82.35.222
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 3
STATUS: RUNNING

NAME: green
LOCATION: us-west1-c
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 35.185.204.26
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 3
STATUS: RUNNING

Your cluster versions might be different depending on when you complete this tutorial.

Get the list of available MasterVersions versions in the zone:

gcloud container get-server-config --location us-west1-b --format=json | jq \
'.validMasterVersions[0:20]'

The output is similar to the following:

[
  "1.24.1-gke.1400",
  "1.23.7-gke.1400",
  "1.23.6-gke.2200",
  "1.23.6-gke.1700",
  "1.23.6-gke.1501",
  "1.23.6-gke.1500",
  "1.23.5-gke.2400",
  "1.23.5-gke.1503",
  "1.23.5-gke.1501",
  "1.22.10-gke.600",
  "1.22.9-gke.2000",
  "1.22.9-gke.1500",
  "1.22.9-gke.1300",
  "1.22.8-gke.2200",
  "1.22.8-gke.202",
  "1.22.8-gke.201",
  "1.22.8-gke.200",
  "1.21.13-gke.900",
  "1.21.12-gke.2200",
  "1.21.12-gke.1700"
]

Get a list of available NodeVersions versions in the zone:

gcloud container get-server-config --location us-west1-b --format=json | jq \
'.validNodeVersions[0:20]'

The output is similar to the following:

[
  "1.24.1-gke.1400",
  "1.23.7-gke.1400",
  "1.23.6-gke.2200",
  "1.23.6-gke.1700",
  "1.23.6-gke.1501",
  "1.23.6-gke.1500",
  "1.23.5-gke.2400",
  "1.23.5-gke.1503",
  "1.23.5-gke.1501",
  "1.22.10-gke.600",
  "1.22.9-gke.2000",
  "1.22.9-gke.1500",
  "1.22.9-gke.1300",
  "1.22.8-gke.2200",
  "1.22.8-gke.202",
  "1.22.8-gke.201",
  "1.22.8-gke.200",
  "1.22.7-gke.1500",
  "1.22.7-gke.1300",
  "1.22.7-gke.900"
]

Set an environment variable for a MasterVersion and NodeVersion version that is in the MasterVersions and NodeVersions lists, and is higher than the current version for the blue cluster, for example:
```
export UPGRADE_VERSION="1.22.10-gke.600"
```
This tutorial uses the 1.22.10-gke.600 version. Your cluster versions might be different depending on the versions that are available when you complete this tutorial. For more information about upgrading, see upgrading clusters and node pools.

Note: It is recommended that you don't skip minor cluster versions to avoid potential control plane or node incompatibility issues. For more information, see Can I skip multiple GKE versions during a cluster upgrade?.

Upgrade the control plane node for the blue cluster:

gcloud container clusters upgrade blue \
    --location us-west1-b --master --cluster-version ${UPGRADE_VERSION}

To confirm the upgrade, press Y.

This process takes a few minutes to complete. Wait until the upgrade is complete before proceeding.

After the update is complete, the output is the following:

Updated
[https://container.googleapis.com/v1/projects/gke-multicluster-upgrades/zones/us-west1-b/clusters/blue].

Upgrade the nodes in the blue cluster:

gcloud container clusters upgrade blue \
    --location=us-west1-b --node-pool=default-pool \
    --cluster-version ${UPGRADE_VERSION}

To confirm the update, press Y.

This process takes a few minutes to complete. Wait until the node upgrade is complete before proceeding.

After the upgrade is complete, the output is the following:

Upgrading blue... Done with 3 out of 3 nodes (100.0%): 3 succeeded...done.
Updated [https://container.googleapis.com/v1/projects/gke-multicluster-upgrades/zones/us-west1-b/clusters/blue].

Verify that the blue cluster is upgraded:

gcloud container clusters list

The output is similar to the following:

NAME: ingress-config
LOCATION: us-west1-a
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 35.233.186.135
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 4
STATUS: RUNNING

NAME: blue
LOCATION: us-west1-b
MASTER_VERSION: 1.22.10-gke.600
MASTER_IP: 34.82.35.222
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.10-gke.600
NUM_NODES: 3
STATUS: RUNNING

NAME: green
LOCATION: us-west1-c
MASTER_VERSION: 1.22.8-gke.202
MASTER_IP: 35.185.204.26
MACHINE_TYPE: e2-medium
NODE_VERSION: 1.22.8-gke.202
NUM_NODES: 3
STATUS: RUNNING

Add the `blue` cluster back to the load balancing pool

In this section, you add the blue cluster back into the load balancing pool.

In Cloud Shell, verify that the application deployment is running on the blue cluster before you add it back to the load balancing pool:

kubectl --context ${BLUE_CLUSTER} get pods

The output is similar to the following:

NAME                                   READY   STATUS    RESTARTS   AGE
whereami-deployment-756c7dc74c-xdnb6   1/1     Running   0          17m

Update the MutliclusterService resource to add the blue cluster back to the load balancing pool:

kubectl --context ${INGRESS_CONFIG_CLUSTER} apply \
        -f ${WORKDIR}/multicluster-manifests/mcs-blue-green.yaml

Verify that you have both blue and green clusters in the clusters specification:

kubectl --context ${INGRESS_CONFIG_CLUSTER} get multiclusterservice \
        -o json | jq '.items[].spec.clusters'

The output is the following:

[
  {
    "link": "us-west1-b/blue"
  },
  {
    "link": "us-west1-c/green"
  }
]

The blue and green clusters are now in the clusters specification.

Metrics from the Cloud Load Balancing metrics are available in the Google Cloud console. Generate the URL:

echo "https://console.cloud.google.com/monitoring/dashboards/builder/${DASH_ID}/?project=${PROJECT}&timeDomain=1h"

In a browser, go to the URL generated by the previous command.

The chart shows that both blue and green clusters are receiving traffic from the load generator using the load balancer.

Note: It may take several minutes for traffic to rebalance.

Congratulations. You successfully upgraded a GKE cluster in a multi-cluster architecture using Multi Cluster Ingress.
To upgrade the green cluster, repeat the process to drain and upgrade the blue cluster, replacing blue with green throughout.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used in this tutorial, either delete the project that contains the resources, or keep the project and delete the individual resources.

The easiest way to eliminate billing is to delete the Google Cloud project that you created for the tutorial. Alternatively, you can delete the individual resources.

Delete the clusters

In Cloud Shell, unregister and delete the blue and green clusters:

gcloud container fleet memberships unregister blue --gke-cluster=us-west1-b/blue
gcloud container clusters delete blue --location us-west1-b --quiet

gcloud container fleet memberships unregister green --gke-cluster=us-west1-c/green
gcloud container clusters delete green --location us-west1-c --quiet

Delete the MuticlusterIngress resource from the ingress-config cluster:
```
kubectl --context ${INGRESS_CONFIG_CLUSTER} delete -f ${WORKDIR}/multicluster-manifests/mci.yaml
```
This command deletes the Cloud Load Balancing resources from the project.

Unregister and delete the ingress-config cluster:

gcloud container fleet memberships unregister ingress-config --gke-cluster=us-west1-a/ingress-config
gcloud container clusters delete ingress-config --location us-west1-a --quiet

Verify all clusters are deleted:
```
gcloud container clusters list
```
The output is the following:
```
*&lt;null&gt;*
```
Reset the kubeconfig file:
```
unset KUBECONFIG
```
Remove the WORKDIR folder:
```
cd ${HOME}
rm -rf ${WORKDIR}
```

Delete the project

In the Google Cloud console, go to the Manage resources page.
Go to Manage resources
In the project list, select the project that you want to delete, and then click Delete.
In the dialog, type the project ID, and then click Shut down to delete the project.

What's next

Learn more about Multi Cluster Ingress.
Learn how to deploy Multi Cluster Ingress across clusters.
Explore reference architectures, diagrams, and best practices about Google Cloud. Take a look at our Cloud Architecture Center.

Upgrading a multi-cluster GKE environment with Multi Cluster Ingress

Architecture

Objectives

Costs

Before you begin

Set up the environment

Create and register GKE clusters to Hub

Create GKE clusters

Register GKE clusters to a fleet

Deploy a sample application to the blue and green clusters

Configure multi-cluster Ingress

Set up the load generator

Monitor traffic

Drain and upgrade the blue cluster

Drain the blue cluster

Upgrade the blue cluster

Add the blue cluster back to the load balancing pool

Clean up

Delete the clusters

Delete the project

What's next

Drain and upgrade the `blue` cluster

Upgrade the `blue` cluster

Add the `blue` cluster back to the load balancing pool