Flagger Install on GKE Istio

This guide walks you through setting up Flagger and Istio on Google Kubernetes Engine.

GKE Cluster Overview


You will be creating a cluster on Google’s Kubernetes Engine (GKE), if you don’t have an account you can sign up here for free credits.

Login into Google Cloud, create a project and enable billing for it.

Install the gcloud command line utility and configure your project with gcloud init.

Set the default project (replace PROJECT_ID with your own project):

gcloud config set project PROJECT_ID

Set the default compute region and zone:

gcloud config set compute/region us-central1
gcloud config set compute/zone us-central1-a

Enable the Kubernetes and Cloud DNS services for your project:

gcloud services enable container.googleapis.com
gcloud services enable dns.googleapis.com

Install the kubectl command-line tool:

gcloud components install kubectl

GKE cluster setup

Create a cluster with the Istio add-on:

K8S_VERSION=$(gcloud container get-server-config --format=json \
| jq -r '.validMasterVersions[0]')
gcloud beta container clusters create istio \
--cluster-version=${K8S_VERSION} \
--zone=us-central1-a \
--num-nodes=2 \
--machine-type=n1-highcpu-4 \
--preemptible \
--no-enable-cloud-logging \
--no-enable-cloud-monitoring \
--disk-size=30 \
--enable-autorepair \
--addons=HorizontalPodAutoscaling,Istio \

The above command will create a default node pool consisting of two n1-highcpu-4 (vCPU: 4, RAM 3.60GB, DISK: 30GB) preemptible VMs. Preemptible VMs are up to 80% cheaper than regular instances and are terminated and replaced after a maximum of 24 hours.

Set up credentials for kubectl:

gcloud container clusters get-credentials istio

Create a cluster admin role binding:

kubectl create clusterrolebinding "cluster-admin-$(whoami)" \
--clusterrole=cluster-admin \
--user="$(gcloud config get-value core/account)"

Validate your setup with:

kubectl -n istio-system get svc

In a couple of seconds GCP should allocate an external IP to the istio-ingressgateway service.

Cloud DNS setup

You will need an internet domain and access to the registrar to change the name servers to Google Cloud DNS.

Create a managed zone named istio in Cloud DNS (replace example.com with your domain):

gcloud dns managed-zones create \
--dns-name="example.com." \
--description="Istio zone" "istio"

Look up your zone's name servers:

gcloud dns managed-zones describe istio

Update your registrar's name server records with the records returned by the above command.

Wait for the name servers to change (replace example.com with your domain):

watch dig +short NS example.com

Create a static IP address named istio-gateway using the Istio ingress IP:

export GATEWAY_IP=$(kubectl -n istio-system get svc/istio-ingressgateway -ojson \
| jq -r .status.loadBalancer.ingress[0].ip)
gcloud compute addresses create istio-gateway --addresses ${GATEWAY_IP} --region us-central1

Create the following DNS records (replace example.com with your domain):

gcloud dns record-sets transaction start --zone=istio
gcloud dns record-sets transaction add --zone=istio \
--name="${DOMAIN}" --ttl=300 --type=A ${GATEWAY_IP}
gcloud dns record-sets transaction add --zone=istio \
--name="www.${DOMAIN}" --ttl=300 --type=A ${GATEWAY_IP}
gcloud dns record-sets transaction add --zone=istio \
--name="*.${DOMAIN}" --ttl=300 --type=A ${GATEWAY_IP}
gcloud dns record-sets transaction execute --zone istio

Verify that the wildcard DNS is working (replace example.com with your domain):

watch host test.example.com

Install Helm

Install the Helm command-line tool:

brew install kubernetes-helm

Create a service account and a cluster role binding for Tiller:

kubectl -n kube-system create sa tiller
kubectl create clusterrolebinding tiller-cluster-rule \
--clusterrole=cluster-admin \

Deploy Tiller in the kube-system namespace:

helm init --service-account tiller

You should consider using SSL between Helm and Tiller, for more information on securing your Helm installation see docs.helm.sh.

Install cert-manager

Jetstack's cert-manager is a Kubernetes operator that automatically creates and manages TLS certs issued by Let’s Encrypt.

You'll be using cert-manager to provision a wildcard certificate for the Istio ingress gateway.

Install cert-manager's CRDs:

kubectl apply -f ${CERT_REPO}/release-0.10/deploy/manifests/00-crds.yaml

Create the cert-manager namespace and disable resource validation:

kubectl create namespace cert-manager
kubectl label namespace cert-manager certmanager.k8s.io/disable-validation=true

Install cert-manager with Helm:

helm repo add jetstack https://charts.jetstack.io && \
helm repo update && \
helm upgrade -i cert-manager \
--namespace cert-manager \
--version v0.10.0 \

Istio Gateway TLS setup

Istio Let's Encrypt

Create a generic Istio Gateway to expose services outside the mesh on HTTPS:

kubectl apply -f ${REPO}/artifacts/gke/istio-gateway.yaml

Create a service account with Cloud DNS admin role (replace my-gcp-project with your project ID):

gcloud iam service-accounts create dns-admin \
--display-name=dns-admin \
gcloud iam service-accounts keys create ./gcp-dns-admin.json \
--iam-account=[email protected]${GCP_PROJECT}.iam.gserviceaccount.com \
gcloud projects add-iam-policy-binding ${GCP_PROJECT} \
--member=serviceAccount:[email protected]${GCP_PROJECT}.iam.gserviceaccount.com \

Create a Kubernetes secret with the GCP Cloud DNS admin key:

kubectl create secret generic cert-manager-credentials \
--from-file=./gcp-dns-admin.json \

Create a letsencrypt issuer for CloudDNS (replace [email protected] with a valid email address and my-gcp-projectwith your project ID):

apiVersion: certmanager.k8s.io/v1alpha1
kind: Issuer
name: letsencrypt-prod
namespace: istio-system
server: https://acme-v02.api.letsencrypt.org/directory
name: letsencrypt-prod
- name: cloud-dns
name: cert-manager-credentials
key: gcp-dns-admin.json
project: my-gcp-project

Save the above resource as letsencrypt-issuer.yaml and then apply it:

kubectl apply -f ./letsencrypt-issuer.yaml

Create a wildcard certificate (replace example.com with your domain):

apiVersion: certmanager.k8s.io/v1alpha1
kind: Certificate
name: istio-gateway
namespace: istio-system
secretName: istio-ingressgateway-certs
name: letsencrypt-prod
commonName: "*.example.com"
- dns01:
provider: cloud-dns
- "*.example.com"
- "example.com"

Save the above resource as istio-gateway-cert.yaml and then apply it:

kubectl apply -f ./istio-gateway-cert.yaml

In a couple of seconds cert-manager should fetch a wildcard certificate from letsencrypt.org:

kubectl -n istio-system describe certificate istio-gateway
Type Reason Age From Message
---- ------ ---- ---- -------
Normal CertIssued 1m52s cert-manager Certificate issued successfully

Recreate Istio ingress gateway pods:

kubectl -n istio-system get pods -l istio=ingressgateway

Note that Istio gateway doesn't reload the certificates from the TLS secret on cert-manager renewal. Since the GKE cluster is made out of preemptible VMs the gateway pods will be replaced once every 24h, if your not using preemptible nodes then you need to manually delete the gateway pods every two months before the certificate expires.

Install Prometheus

The GKE Istio add-on does not include a Prometheus instance that scrapes the Istio telemetry service. Because Flagger uses the Istio HTTP metrics to run the canary analysis you have to deploy the following Prometheus configuration that's similar to the one that comes with the official Istio Helm chart.

Find the GKE Istio version with:

kubectl -n istio-system get deploy istio-pilot -oyaml | grep image:

Install Prometheus in istio-system namespace:

kubectl -n istio-system apply -f \

Install Flagger and Grafana

Add Flagger Helm repository:

helm repo add flagger https://flagger.app

Install Flagger's Canary CRD:

kubectl apply -f https://raw.githubusercontent.com/fluxcd/flagger/main/artifacts/flagger/crd.yaml

Deploy Flagger in the istio-system namespace with Slack notifications enabled:

helm upgrade -i flagger flagger/flagger \
--namespace=istio-system \
--set crd.create=false \
--set metricsServer=http://prometheus.istio-system:9090 \
--set slack.url=https://hooks.slack.com/services/YOUR/SLACK/WEBHOOK \
--set slack.channel=general \
--set slack.user=flagger

Deploy Grafana in the istio-system namespace:

helm upgrade -i flagger-grafana flagger/grafana \
--namespace=istio-system \
--set url=http://prometheus.istio-system:9090 \
--set user=admin \
--set password=replace-me

Expose Grafana through the public gateway by creating a virtual service (replace example.com with your domain):

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
name: grafana
namespace: istio-system
- "grafana.example.com"
- public-gateway.istio-system.svc.cluster.local
- route:
- destination:
host: flagger-grafana

Save the above resource as grafana-virtual-service.yaml and then apply it:

kubectl apply -f ./grafana-virtual-service.yaml

Navigate to http://grafana.example.com in your browser and you should be redirected to the HTTPS version.