This code is a companion to the Intro to Istio video from the developerWorks Mailbag series. You can find the basics of the project here, but the video is your source for complete guidance and a full explanation of what you'll do here.

This repo contains the code to illustrate two concepts of the Istio service mesh: sidecar proxies and route rules. It does this with a horoscope service. There are five different Docker images, each of which provides a different horoscope. All five implement the same interface, and the code creates a Kubernetes service that acts as a front-end to the five Docker containers (or pods, in Kubernetes terminology).

When you create the service, you'll use the istioctl command to inject sidecar proxies next to all the services and deployments you create. That lets you control access to the service. At the end, we'll create some route rules that control how traffic is distributed amongst the five horoscopes.

There are three things you have to do before you get started:

1. Create a Kubernetes cluster with the IBM Container service. From the IBM Cloud dashboard, choose Containers in the dropdown menu in the upper left. A free cluster will work just fine. And the price is right. (Be aware it may take up to 20 minutes before the cluster is ready.)
2. On the command line, use bx login to log in to the IBM Cloud.
3. On the command line, use bx cs cluster-config Mailbag to configure the kubectl command. (That assumes your cluster is named Mailbag, of course.)

There's a developerWorks mailbag video on Kubernetes if you need a refresher on these things.

To install Istio, visit istio.io and download the latest zip file or tarball for your platform. Unzip it and go to the install/kubernetes directory. Type kubectl create -f istio.yaml to install Istio.

The file horoscope.yaml in the root directory of this repo installs all of the code. The horoscope implementations in the five subdirectories are all packaged as Docker images in yr author's Dockerhub account, so you don't have to build or upload them yourself. Run this command to do all the initial setup:

kubectl create -f <(istioctl kube-inject -f horoscope.yaml)

The kube-inject option of the istioctl command modifies the YAML to inject the sidecar proxies Istio needs to do its work. That creates the services and deployments your app needs; now you have to define an ingress so Istio will let incoming traffic reach your service. Use this command:

kubectl create -f ingress.yaml

Now you should be able to curl to the service...but you have to get the IP address of the cluster and the randomly-assigned port number for the istio-ingress service. You can get the IP address with the bx cs workers Mailbag command. The port number comes from kubectl get svc istio-ingress -n istio-system - look for the port number assigned to port 80. (Istio installs itself in the namespace istio-system, so you have use -n to specify the namespace whenever you're looking for Istio components. )

To curl the service, type curl {ip_address}:{port}/horoscope/gemini to get the horoscope for Gemini. If you run this several times with the same sign, you'll get the five different versions of the horoscope. If you try it with other signs, you'll obviously get other results as well.

Note: If you use a paid cluster, you get both the IP address and the port from kubectl get svc istio-ingress -n istio-system. A paid cluster has an external load balancer, so istio-ingress has an external IP address.

Note: Yr author is not an Angular expert by any means, so tread with caution here. Installing Angular can be tedious. ("Whaddya mean sudo doesn't have permissions to create a directory???") Let me know if you have any problems and I'll do my best to help, but Stack Overflow is your friend here.

Before you can run the UI, you'll need to change the IP address and port number in the file angular-ui/src/app/horoscope-service.ts. Save the file and (heh) everything should work.

If you switch to the angular-ui directory and type npm install followed by ng serve, you should be able to go to http://localhost:4200 to see the app. Note that because of the way Angular applications work, you can kill ng serve once the page loads. All of the interactions between the Angular app and the horoscope service are handled client-side.

If you run the command kubectl create -f route-optimistic-ominous.yaml, you'll create a route rule that divides the traffic between the Ominous service and the Optimistic service, 50% for each. Invoke the service a few times (either via the Angular app or curl) and you'll see the results. The command kubectl replace -f route-john-swanson.yaml sends 100% of the traffic to the John Swanson service. You can type kubectl delete -f routerule horoscope to restore the original configuration.