When introducing new versions of a service, it is often desirable to shift a controlled percentage of user traffic to a newer version of the service in the process of phasing out the older version. This technique is called a canary deployment.
Kubernetes cluster operators can orchestrate canary deployments natively using labels and Deployments. This technique has certain limitations, however: traffic distribution and replica counts are coupled, which in practice means replica ratios must be controlled manually in order to limit traffic to the canary release. In other words, to direct 10% of traffic to a canary deployment, you would need to have a pool of ten pods, with one pod receiving 10% of user traffic, and the other nine receiving the rest.
Deploying with an Istio service mesh can address this issue by enabling a clear separation between replica counts and traffic management. The Istio mesh allows fine-grained traffic control that decouples traffic distribution and management from replica scaling. Instead of manually controlling replica ratios, you can define traffic percentages and targets, and Istio will manage the rest.
In this tutorial, you will create a canary deployment using Istio and Kubernetes. You will deploy two versions of a demo Node.js application, and use Virtual Service and Destination Rule resources to configure traffic routing to both the newer and older versions. This will be a good starting point to build out future canary deployments with Istio.
- A Kubernetes 1.10+ cluster with role-based access control (RBAC) enabled. This setup will use a DigitalOcean Kubernetes cluster with three nodes, but you are free to create a cluster using another method.
Note: We highly recommend a cluster with at least 8GB of available memory and 4vCPUs for this setup. This tutorial will use three of DigitalOcean's standard 4GB/2vCPU Droplets as nodes.
kubectlcommand-line tool installed on a development server and configured to connect to your cluster. You can read more about installing
kubectlin the official documentation.
- Docker installed on your development server. If you are working with Ubuntu 18.04, follow Steps 1 and 2 of How To Install and Use Docker on Ubuntu 18.04; otherwise, follow the official documentation for information about installing on other operating systems. Be sure to add your non-root user to the
dockergroup, as described in Step 2 of the linked tutorial.
- A Docker Hub account. For an overview of how to set this up, refer to this introduction to Docker Hub.
- Istio installed and configured following the instructions in How To Install and Use Istio With Kubernetes. You should also have the Grafana telemetry addon enabled and configured for external access.
Step 1 — Packaging the Application
In the prerequisite tutorial, How To Install and Use Istio With Kubernetes, you created a
node-demo Docker image to run a shark information application and pushed this image to Docker Hub. In this step, you will create another image: a newer version of the application that you will use for your canary deployment.
Our original demo application emphasized some friendly facts about sharks on its Shark Info page:
But we have decided in our new canary version to emphasize some scarier facts:
Our first step will be to clone the code for this second version of our application into a directory called
node_image. Using the following command, clone the nodejs-canary-app repository from the DigitalOcean Community GitHub account. This repository contains the code for the second, scarier version of our application:
- git clone https://github.com/do-community/nodejs-canary-app.git node_image
Navigate to the
- cd node_image
This directory contains files and folders for the newer version of our shark information application, which offers users information about sharks, like the original application, but with an emphasis on scarier facts. In addition to the application files, the directory contains a Dockerfile with instructions for building a Docker image with the application code. For more information about the instructions in the Dockerfile, see Step 3 of How To Build a Node.js Application with Docker.
To test that the application code and Dockerfile work as expected, you can build and tag the image using the
docker build command, and then use the image to run a demo container. Using the
-t flag with
docker build will allow you to tag the image with your Docker Hub username so that you can push it to Docker Hub once you've tested it.
Build the image with the following command:
- docker build -t your_dockerhub_username/node-demo-v2 .
. in the command specifies that the build context is the current directory. We've named the image
node-demo-v2, to reference the
node-demo image we created in How To Install and Use Istio With Kubernetes.
Once the build process is complete, you can list your images with
- docker images
You will see the following output confirming the image build:
OutputREPOSITORY TAG IMAGE ID CREATED SIZE your_dockerhub_username/node-demo-v2 latest 37f1c2939dbf 5 seconds ago 77.6MB node 10-alpine 9dfa73010b19 2 days ago 75.3MB
Next, you'll use
docker run to create a container based on this image. We will include three flags with this command:
-p: This publishes the port on the container and maps it to a port on our host. We will use port
80on the host, but you should feel free to modify this as necessary if you have another process running on that port. For more information about how this works, see this discussion in the Docker docs on port binding.
-d: This runs the container in the background.
--name: This allows us to give the container a customized name.
Run the following command to build the container:
- docker run --name node-demo-v2 -p 80:8080 -d your_dockerhub_username/node-demo-v2
Inspect your running containers with
- docker ps
You will see output confirming that your application container is running:
OutputCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 49a67bafc325 your_dockerhub_username/node-demo-v2 "docker-entrypoint.s…" 8 seconds ago Up 6 seconds 0.0.0.0:80->8080/tcp node-demo-v2
You can now visit your server IP in your browser to test your setup:
http://your_server_ip. Your application will display the following landing page:
Click on the Get Shark Info button to get to the scarier shark information:
Now that you have tested the application, you can stop the running container. Use
docker ps again to get your
- docker ps
OutputCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 49a67bafc325 your_dockerhub_username/node-demo-v2 "docker-entrypoint.s…" About a minute ago Up About a minute 0.0.0.0:80->8080/tcp node-demo-v2
Stop the container with
docker stop. Be sure to replace the
CONTAINER ID listed here with your own application
- docker stop 49a67bafc325
Now that you have tested the image, you can push it to Docker Hub. First, log in to the Docker Hub account you created in the prerequisites:
- docker login -u your_dockerhub_username
When prompted, enter your Docker Hub account password. Logging in this way will create a
~/.docker/config.json file in your non-root user's home directory with your Docker Hub credentials.
Push the application image to Docker Hub with the
docker push command. Remember to replace
your_dockerhub_username with your own Docker Hub username:
- docker push your_dockerhub_username/node-demo-v2
You now have two application images saved to Docker Hub: the
node-demo image, and
node-demo-v2. We will now modify the manifests you created in the prerequisite tutorial How To Install and Use Istio With Kubernetes to direct traffic to the canary version of your application.
Step 2 — Modifying the Application Deployment
In How To Install and Use Istio With Kubernetes, you created an application manifest with specifications for your application Service and Deployment objects. These specifications describe each object's desired state. In this step, you will add a Deployment for the second version of your application to this manifest, along with version labels that will enable Istio to manage these resources.
When you followed the setup instructions in the prerequisite tutorial, you created a directory called
istio_project and two
node-app.yaml, which contains the specifications for your Service and Deployment objects, and
node-istio.yaml, which contains specifications for your Istio Virtual Service and Gateway resources.
Navigate to the
istio_project directory now:
- cd istio_project
nano or your favorite editor to make changes to your application manifest:
- nano node-app.yaml
Currently, the file looks like this:
apiVersion: v1 kind: Service metadata: name: nodejs labels: app: nodejs spec: selector: app: nodejs ports: - name: http port: 8080 --- apiVersion: apps/v1 kind: Deployment metadata: name: nodejs labels: version: v1 spec: replicas: 1 selector: matchLabels: app: nodejs template: metadata: labels: app: nodejs version: v1 spec: containers: - name: nodejs image: your_dockerhub_username/node-demo ports: - containerPort: 8080
For a full explanation of this file's contents, see Step 3 of How To Install and Use Istio With Kubernetes.
We have already included version labels in our Deployment
template fields, following Istio's recommendations for Pods and Services. Now we can add specifications for a second Deployment object, which will represent the second version of our application, and make a quick modification to the
name of our first Deployment object.
First, change the name of your existing Deployment object to
... apiVersion: apps/v1 kind: Deployment metadata: name: nodejs-v1 labels: version: v1 ...
Next, below the specifications for this Deployment, add the specifications for your second Deployment. Remember to add the name of your own image to the
... --- apiVersion: apps/v1 kind: Deployment metadata: name: nodejs-v2 labels: version: v2 spec: replicas: 1 selector: matchLabels: app: nodejs template: metadata: labels: app: nodejs version: v2 spec: containers: - name: nodejs image: your_dockerhub_username/node-demo-v2 ports: - containerPort: 8080
Like the first Deployment, this Deployment uses a
version label to specify the version of the application that corresponds to this Deployment. In this case,
v2 will distinguish the application version associated with this Deployment from
v1, which corresponds to our first Deployment.
We've also ensured that the Pods managed by the
v2 Deployment will run the
node-demo-v2 canary image, which we built in the previous Step.
Save and close the file when you are finished editing.
With your application manifest modified, you can move on to making changes to your
Step 3 — Weighting Traffic with Virtual Services and Adding Destination Rules
In How To Install and Use Istio With Kubernetes, you created Gateway and Virtual Service objects to allow external traffic into the Istio mesh and route it to your application Service. Here, you will modify your Virtual Service configuration to include routing to your application Service subsets —
v2. You will also add a Destination Rule to define additional, version-based policies to the routing rules you are applying to your
nodejs application Service.
- nano node-istio.yaml
Currently, the file looks like this:
apiVersion: networking.istio.io/v1alpha3 kind: Gateway metadata: name: nodejs-gateway spec: selector: istio: ingressgateway servers: - port: number: 80 name: http protocol: HTTP hosts: - "*" --- apiVersion: networking.istio.io/v1alpha3 kind: VirtualService metadata: name: nodejs spec: hosts: - "*" gateways: - nodejs-gateway http: - route: - destination: host: nodejs
For a complete explanation of the specifications in this manifest, see Step 4 of How To Install and Use Istio With Kubernetes.
Our first modification will be to the Virtual Service. Currently, this resource routes traffic entering the mesh through our
nodejs-gateway to our
nodejs application Service. What we would like to do is configure a routing rule that will send 80% of traffic to our original application, and 20% to the newer version. Once we are satisfied with the canary's performance, we can reconfigure our traffic rules to gradually send all traffic to the newer application version.
Instead of routing to a single
destination, as we did in the original manifest, we will add
destination fields for both of our application subsets: the original version (
v1) and the canary (
Make the following additions to the Virtual Service to create this routing rule:
... apiVersion: networking.istio.io/v1alpha3 kind: VirtualService metadata: name: nodejs spec: hosts: - "*" gateways: - nodejs-gateway http: - route: - destination: host: nodejs subset: v1 weight: 80 - destination: host: nodejs subset: v2 weight: 20
The policy that we have added includes two destinations: the
subset of our
nodejs Service that is running the original version of our application,
v1, and the
subset that is running the canary,
v2. Subset one will receive 80% of incoming traffic, while the canary will receive 20%.
Next, we will add a Destination Rule that will apply rules to incoming traffic after that traffic has been routed to the appropriate Service. In our case, we will configure
subset fields to send traffic to Pods with the appropriate version labels.
Add the following code below your Virtual Service definition:
... --- apiVersion: networking.istio.io/v1alpha3 kind: DestinationRule metadata: name: nodejs spec: host: nodejs subsets: - name: v1 labels: version: v1 - name: v2 labels: version: v2
Our Rule ensures that traffic to our Service subsets,
v2, reaches Pods with the appropriate labels:
version: v1 and
version: v2. These are the labels that we included in our application Deployment specs.
If we wanted, however, we could also apply specific traffic policies at the subset level, enabling further specificity in our canary deployments. For additional information about defining traffic policies at this level, see the official Istio documentation.
Save and close the file when you have finished editing.
With your application manifests revised, you are ready to apply your configuration changes and examine your application traffic data using the Grafana telemetry addon.
Step 4 — Applying Configuration Changes and Accessing Traffic Data
The application manifests are updated, but we still need to apply these changes to our Kubernetes cluster. We'll use the
kubectl apply command to apply our changes without completely overwriting the existing configuration. After doing this, you will be able to generate some requests to your application and look at the associated data in your Istio Grafana dashboards.
Apply your configuration to your application Service and Deployment objects:
- kubectl apply -f node-app.yaml
You will see the following output:
Outputservice/nodejs unchanged deployment.apps/nodejs-v1 created deployment.apps/nodejs-v2 created
Next, apply the configuration updates you've made to
node-istio.yaml, which include the changes to the Virtual Service and the new Destination Rule:
- kubectl apply -f node-istio.yaml
You will see the following output:
Outputgateway.networking.istio.io/nodejs-gateway unchanged virtualservice.networking.istio.io/nodejs configured destinationrule.networking.istio.io/nodejs created
You are now ready to generate traffic to your application. Before doing that, however, first check to be sure that you have the
grafana Service running:
- kubectl get svc -n istio-system | grep grafana
Outputgrafana ClusterIP 10.245.233.51 <none> 3000/TCP 4d2h
Also check for the associated Pods:
- kubectl get svc -n istio-system | grep grafana
Outputgrafana-67c69bb567-jpf6h 1/1 Running 0 4d2h
Finally, check for the
grafana-gateway Gateway and
grafana-vs Virtual Service:
- kubectl get gateway -n istio-system | grep grafana
- kubectl get virtualservice -n istio-system | grep grafana
Outputgrafana-vs [grafana-gateway] [*] 4d2h
If you don't see output from these commands, check Steps 2 and 5 of How To Install and Use Istio With Kubernetes, which discuss how to enable the Grafana telemetry addon when installing Istio and how to enable HTTP access to the Grafana Service.
You can now access your application in the browser. To do this, you will need the external IP associated with your
istio-ingressgateway Service, which is a LoadBalancer Service type. We matched our
nodejs-gateway Gateway with this controller when writing our Gateway manifest in How To Install and Use Istio With Kubernetes. For more detail on the Gateway manifest, see Step 4 of that tutorial.
Get the external IP for the
istio-ingressgateway Service with the following command:
- kubectl get svc -n istio-system
You will see output like the following:
OutputNAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE grafana ClusterIP 10.245.85.162 <none> 3000/TCP 42m istio-citadel ClusterIP 10.245.135.45 <none> 8060/TCP,15014/TCP 42m istio-galley ClusterIP 10.245.46.245 <none> 443/TCP,15014/TCP,9901/TCP 42m istio-ingressgateway LoadBalancer 10.245.171.39 ingressgateway_ip 15020:30707/TCP,80:31380/TCP,443:31390/TCP,31400:31400/TCP,15029:30285/TCP,15030:31668/TCP,15031:32297/TCP,15032:30853/TCP,15443:30406/TCP 42m istio-pilot ClusterIP 10.245.56.97 <none> 15010/TCP,15011/TCP,8080/TCP,15014/TCP 42m istio-policy ClusterIP 10.245.206.189 <none> 9091/TCP,15004/TCP,15014/TCP 42m istio-sidecar-injector ClusterIP 10.245.223.99 <none> 443/TCP 42m istio-telemetry ClusterIP 10.245.5.215 <none> 9091/TCP,15004/TCP,15014/TCP,42422/TCP 42m prometheus ClusterIP 10.245.100.132 <none> 9090/TCP 42m
istio-ingressgateway should be the only Service with the
LoadBalancer, and the only Service with an external IP.
Navigate to this external IP in your browser:
You should see the following landing page:
Click on Get Shark Info button. You will see one of two shark information pages:
Click refresh on this page a few times. You should see the friendlier shark information page more often than the scarier version.
Once you have generated some load by refreshing five or six times, you can head over to your Grafana dashboards.
In your browser, navigate to the following address, again using your
istio-ingressgateway external IP and the port that's defined in the Grafana Gateway manifest:
You will see the following landing page:
Clicking on Home at the top of the page will bring you to a page with an istio folder. To get a list of dropdown options, click on the istio folder icon:
From this list of options, click on Istio Service Dashboard.
This will bring you to a landing page with another dropdown menu:
nodejs.default.svc.cluster.local from the list of available options.
If you navigate down to the Service Workloads section of the page, you will be able to look at Incoming Requests by Destination And Response Code:
Here, you will see a combination of 200 and 304 HTTP response codes, indicating successful
Not Modified responses. The responses labeled
nodejs-v1 should outnumber the responses labeled
nodejs-v2, indicating that incoming traffic is being routed to our application subsets following the parameters we defined in our manifests.
In this tutorial, you deployed a canary version of a demo Node.js application using Istio and Kubernetes. You created Virtual Service and Destination Rule resources that together allowed you to send 80% of your traffic to your original application service, and 20% to the newer version. Once you are satisfied with the performance of the newer application version, you can update your configuration settings as desired.
For more information about traffic management in Istio, see the related high-level overview in the documentation, as well as specific examples that use Istio's
helloworld sample applications.