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Zone Printer

Zone printer is an application that displays the Google Cloud Platform (GCP) zone where the application is running.

How does it work?

Note: This section explains how the application is setup. Feel free to skip to the next section if you don't care about these details.

Zone printer is intended to be run in a Kubernetes cluster and is composed of: a ConfigMap (app/zonefetch.yaml), a Deployment (app/nginx-dep.yaml) and a Service (app/nginx-svc.yaml).

The ConfigMap consists of a script that fetches GCP zone information from the GCE metadata server. The Deployment consists of a pod spec with two containers. One container mounts the aforementioned ConfigMap, executes the script in the ConfigMap and writes the output to /usr/share/nginx/html/index.html. The other container runs a standard nginx server that reads from /usr/share/nginx/html/.

The pod, therefore, exposes the fetched zone information at / or /index.html HTTP paths.

The Service exposes the Deployment pods on port 30061 on all the nodes in its Kubernetes cluster.

The example also includes an Ingress manifest (ingress/nginx.yaml) that will be used by kubemci.

Tutorial

0. Prerequisite

0.1 GCP Project

Ensure you that you have a GCP Project. If you don't have one already, you can create a project by following the instructions at Creating and Managing Projects.

After your project is created, run the following command in your terminal:

PROJECT=<your-project-name>

0.2 gcloud installed and initialized

You can install gcloud by following the instructions at Installing Cloud SDK and initialize it by running the following commands:

gcloud init # Set $PROJECT as the default project
gcloud auth login
gcloud auth application-default login

0.3 kubectl

You can install kubectl by running:

gcloud components install kubectl

0.4 Kubernetes clusters on GCP

Existing clusters

Note:: If you don't already have Kubernetes cluster on GCP, skip to the next subsection on creating new clusters.

kubemci requires Kubernetes clusters that are v1.8.1 or newer. Please ensure that all the clusters you are using in this tutorial satisfy the minimum version requirement. You can check your cluster version using the kubectl version command.

If you already have clusters with their credentials in your local kubeconfig ($HOME/.kube/config by default) file, you need to ensure that you either only have clusters you are going to use for this tutorial in your default kubeconfig file or create a new kubeconfig file that just contains credentials for those clusters. Assuming that the clusters you are going to use for this tutorial are called us-east, eu-west and asia-east.

List the contexts available (note the names of the ones you wish to use with kubemci)

$ kubectl config get-contexts -o name
us-east
eu-west
asia-east
i-dont-care
doesnt-exist

Now iterate over the contexts you identified, making it the context in-use and then extracting that context to its own file.

# First, do this for the us-east one.
kubectl config use-context us-east
kubectl config view --minify --flatten > mciuseast

# Second, do this for the eu-west one.
kubectl config use-context eu-west
kubectl config view --minify --flatten > mcieuwest

# Finally, do this for the asia-east one.
kubectl config use-context asia-east
kubectl config view --minify --flatten > mciasiaeast

Combine (flatten) all of these extracted contexts to create a single kubeconfig file with just the contexts we care about

# Use KUBECONFIG to specify the context filenames we created in
# the previous step
KUBECONFIG=mciuseast:mcieuwest:mciasiaeast kubectl config view \
  --flatten > zpkubeconfig

Creating new clusters

You need at least two Kubernetes clusters in two different GCP zones to verify that kubemci works. Clusters must be v1.8.1 or newer. Let's create three GKE clusters and get their credentials for the purposes of this tutorial:

# Create a cluster in us-east and get its credentials
gcloud container clusters create \
    --cluster-version=1.8.4-gke.1 \
    --zone=us-east4-a \
    cluster-us-east

KUBECONFIG=./zpkubeconfig gcloud container clusters get-credentials \
    --zone=us-east4-a \
    cluster-us-east


# Create a cluster in eu-west and get its credentials
gcloud container clusters create \
    --cluster-version=1.8.4-gke.1 \
    --zone=europe-west1-c \
    cluster-eu-west

KUBECONFIG=./zpkubeconfig gcloud container clusters get-credentials \
    --zone=europe-west1-c \
    cluster-eu-west


# Create a cluster in asia-east and get its credentials
gcloud container clusters create \
    --cluster-version=1.8.4-gke.1 \
    --zone=asia-east1-b \
    cluster-asia-east

KUBECONFIG=./zpkubeconfig gcloud container clusters get-credentials \
    --zone=asia-east1-b \
    cluster-asia-east

1. Deploy the application

Deploy the application along with its NodePort service in each of the three clusters. You can get the cluster contexts from kubectl config get-contexts and iterate through all the clusters to deploy the application manifests. This could be accomplished by running the following loop:

for ctx in $(kubectl config get-contexts --kubeconfig=./zpkubeconfig -o name); do
  kubectl --context="${ctx}" create -f app/
done

2. Reserve a static IP on GCP.

We need to reserve a static IP on GCP for kubemci. Run the following command to reserve the IP.

ZP_KUBEMCI_IP="zp-kubemci-ip"
gcloud compute addresses create --global "${ZP_KUBEMCI_IP}"

3. Modify the Ingress manifest.

Replace the value of kubernetes.io/ingress.global-static-ip-name annotation in ingress/nginx.yaml with the value of $ZP_KUBEMCI_IP.

sed -i -e "s/\$ZP_KUBEMCI_IP/${ZP_KUBEMCI_IP}/" ingress/nginx.yaml

4. Deploy the Multi-Cluster Ingress (with kubemci)

Run kubemci to create the multi-cluster ingress.

kubemci create zone-printer \
    --ingress=ingress/nginx.yaml \
    --gcp-project=$PROJECT \
    --kubeconfig=./zpkubeconfig

Voila! You should have a multi-cluster ingress once the command successfully exits!

5. Get the status of Multi-Cluster Ingress

You can get the status of the multi-cluster ingress you just created by using kubemci get-status command.

kubemci get-status zone-printer --gcp-project=$PROJECT

6. Test the Multicluster Ingress

It may take several minutes for the ingress to propagate, but once it does, you can test it by curl'ing the IP from the get-status command. You should see it report a zone from the nearest region.

7. Clean up

Delete the multi-cluster ingress by using the kubemci delete command.

kubemci delete zone-printer \
    --ingress=ingress/nginx.yaml \
    --gcp-project=$PROJECT \
    --kubeconfig=./zpkubeconfig

Delete the GKE clusters if you created them earlier in this tutorial and you don't need them any more.

gcloud container clusters delete \
    --zone=us-east4-a \
    cluster-us-east

gcloud container clusters delete \
    --zone=europe-west1-c \
    cluster-eu-west

gcloud container clusters delete \
    --zone=asia-east1-b \
    cluster-asia-east