The API gateway pattern has been used as a part of modern software systems for years. A different concept, service mesh, has also emerged over the last couple of years. They share some similarities in their feature set, and service meshes soon started to introduce their own API gateway implementations. In this post, we'll discuss the Istio ingress gateway, from an API gateway perspective. We'll examine its feature set compared to typical API gateway features. Lastly, we'll demonstrate some of its features on Google's microservices demo application using Backyards (now Cisco Service Mesh Manager), which is Banzai Cloud's production ready [Istio distribution].

API Gateway pattern

What is an API Gateway?

An API gateway is a service that sits between clients and application services. It is the single entry point for all clients when accessing an application. It acts as a reverse proxy for the acceptance of all incoming API calls, routes the requests to the appropriate application services and then returns their results.

What features does it offer?

The API gateway pattern provides the following features: There are different API Gateway implementations available which implement the API gateway pattern. The number and availability of the features listed above depends on which specific implementation is being used. In this post, we'll concentrate on the Istio ingress gateway API gateway implementation.

Istio's API Gateway

Service meshes in general and Istio as well were primarily designed to manipulate, observe and secure in-cluster (east-west) traffic flows. On the other hand, API gateways were designed to handle external (north-south) traffic and route them to internal application services. However, there was, from very early, a recognized need for handling external traffic in Istio, and, since those early days, Istio has supported ingress (and egress) gateways. As a result, Istio has a custom ingress controller implementation which realizes API gateway implementation on its own.

To learn more about Kubernetes ingress APIs and controllers, check out this blog post: Kubernetes ingress, deep dive. If you are interested in Istio's Ingress implementation in more detail, please refer to this post: An in-depth intro to Istio Ingress.

The Istio ingress is an API gateway implementation which accepts client calls and routes them to the application services inside the mesh. Let's see how the features of an Istio ingress gateway can provide compared to a typical API Gateway: As you can see, Istio's ingress implements quite a few of these features. If these features are enough for your use case, then it's advisable that you use Istio ingress gateway as your API gateway alongside your service mesh. If not, then it's also possible for you to use a different API gateway implementation alongside Istio to fill the feature gap. However, it's important to note that the feature gap is closing over time. In the past, fewer of these features had been made available by Istio ingress and, in the future, a few more will be added (e.g. rate limiting).

Backyards (now Cisco Service Mesh Manager)' API gateway

Even though Istio's ingress gateway can provide a lot of API gateway features, it doesn't mean that it is easy to configure, secure and monitor them by default. To help you with that, in Backyards (now Cisco Service Mesh Manager), we've built a lightweight API gateway management tool to complement Istio's API gateway features by adding a UI for easier configuration of routing, TLS certificate handling and ingress monitoring.

It is important to note here that Backyards' lightweight API gateway solution is 100% compatible with, and based on, Istio's ingress gateway. So all the features provided by Istio ingress are available, as should be the case for the future.

The Backyards API gateway dashboard gives you a monitoring and management interface for your Istio gateways with the following features:

• Managing port and host configurations
• Managing TLS certificates
• Managing routing configurations
• Monitoring

Try it out!

We'll deploy Google's online shop microservices demo application on a Kubernetes cluster, then with Backyards (now Cisco Service Mesh Manager), we'll setup an Istio ingress gateway for it with monitoring, routing and TLS certificates.

Setup

1. Create a Kubernetes cluster.

   If you need a hand with that, you can create a cluster with our free version of Banzai Cloud's Pipeline platform.

2. Point KUBECONFIG at your cluster.
3. Install Backyards:{{< include-headless "doc/note-evaluation-suspended.md" >}}{{< include-headless "download-backyards-install.md" >}}
4. Create the hipstershop namespace for our example applications:

   kubectl create ns hipstershop

5. Enable sidecar-injection for the hipstershop namespace:

   backyards sidecar-proxy auto-inject on hipstershop

6. Make sure that the hipstershop namespace has the necessary istio-injection=enabled label. (If it is not there yet, wait a few seconds and check again.)

   kubectl get ns hipstershop --show-labels

7. Install Google's HipsterShop example application in the hipstershop namespace:

   kubectl -n=hipstershop apply -f https://raw.githubusercontent.com/GoogleCloudPlatform/microservices-demo/master/release/kubernetes-manifests.yaml

8. Make sure that the pods are up and running after a minute or so (with 2/2 containers, indicating that Envoy sidecar proxies were successfully injected):

   kubectl -n=hipstershop get po
   NAME                                     READY   STATUS    RESTARTS   AGE
   adservice-687b58699c-x7l5t               2/2     Running   0          113s
   cartservice-778cffc8f6-tzmgf             2/2     Running   2          114s
   checkoutservice-98cf4f4c-477c7           2/2     Running   0          116s
   currencyservice-c69c86b7c-j5h7c          2/2     Running   0          114s
   emailservice-5db6c8b59f-qh6dl            2/2     Running   0          117s
   frontend-8d8958c77-xkkwv                 2/2     Running   0          115s
   loadgenerator-6bf9fd5bc9-xf4cj           2/2     Running   4          114s
   paymentservice-698f684cf9-dfcv7          2/2     Running   0          115s
   productcatalogservice-789c77b8dc-vhjzq   2/2     Running   0          115s
   recommendationservice-75d7cd8d5c-drpn8   2/2     Running   0          116s
   redis-cart-5f59546cdd-p9pzd              2/2     Running   0          113s
   shippingservice-7d87945947-45nx5         2/2     Running   0          113s

9. Open the Backyards dashboard with:

   backyards dashboard

10. Choose the hipstershop namespace in the namespace selector on Backyards' TOPOLOGY view. You should see that the app is up and running already:

Host, port and TLS configurations

1. Apply the following MeshGateway resource to create a separate Istio ingressgateway for our HipsterShop application (this will be the API gateway we configure for our app).

   apiVersion: istio.banzaicloud.io/v1beta1
   kind: MeshGateway
   metadata:
     name: hipstershop-ingress
     namespace: hipstershop
   spec:
     maxReplicas: 1
     minReplicas: 1
     ports:
       - name: http
         port: 80
         protocol: TCP
         targetPort: 8080
       - name: https
         port: 443
         protocol: TCP
         targetPort: 8443
     serviceType: LoadBalancer
     type: ingress
     labels:
       app: hipstershop-ingress

   To read more on the MeshGateway resource and on how to setup multiple gateways with Backyards, see the Istio ingress and egress gateways blog post.

2. Navigate to the GATEWAYS page on the Backyards dashboard where you should see the hipstershop-ingress gateway we've just created.
3. Click on CREATE NEW to create a host and port configuration where you'd like to access the app externally. With Backyards, you can simply generate a subdomain under .banzaicloud.io and with a single click have a valid Let's Encrypt certificate generated for it. Finally, click on CREATE:
4. After a short while you should see a green checkmark indicating that the certificate has been issued and it is valid.

Routing configurations

1. Click on the ROUTES tab and on CREATE NEW. Provide the host field you selected earlier and setup a route for the frontend service, then click CREATE:
2. The routing rule should route all traffic to the frontend service when accessing the specified domain name:
3. Open the chosen url in a browser with https:// and check to makes sure the online shop app is accessible and a valid certificate has been issued:
4. Deploy a new version of the frontend service (frontendv2) so that we can route traffic for that version as well:

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: frontendv2
   spec:
     selector:
       matchLabels:
         app: frontendv2
     template:
       metadata:
         labels:
           app: frontendv2
         annotations:
           sidecar.istio.io/rewriteAppHTTPProbers: "true"
       spec:
         containers:
           - name: server
             image: gcr.io/google-samples/microservices-demo/frontend:v0.1.5
             ports:
               - containerPort: 8080
             readinessProbe:
               initialDelaySeconds: 10
               httpGet:
                 path: "/_healthz"
                 port: 8080
                 httpHeaders:
                   - name: "Cookie"
                     value: "shop_session-id=x-readiness-probe"
             livenessProbe:
               initialDelaySeconds: 10
               httpGet:
                 path: "/_healthz"
                 port: 8080
                 httpHeaders:
                   - name: "Cookie"
                     value: "shop_session-id=x-liveness-probe"
             env:
               - name: PORT
                 value: "8080"
               - name: PRODUCT_CATALOG_SERVICE_ADDR
                 value: "productcatalogservice:3550"
               - name: CURRENCY_SERVICE_ADDR
                 value: "currencyservice:7000"
               - name: CART_SERVICE_ADDR
                 value: "cartservice:7070"
               - name: RECOMMENDATION_SERVICE_ADDR
                 value: "recommendationservice:8080"
               - name: SHIPPING_SERVICE_ADDR
                 value: "shippingservice:50051"
               - name: CHECKOUT_SERVICE_ADDR
                 value: "checkoutservice:5050"
               - name: AD_SERVICE_ADDR
                 value: "adservice:9555"
               - name: ENV_PLATFORM
                 value: "gcp"
             resources:
               requests:
                 cpu: 100m
                 memory: 64Mi
               limits:
                 cpu: 200m
                 memory: 128Mi
   ---
   apiVersion: v1
   kind: Service
   metadata:
     name: frontendv2
   spec:
     type: ClusterIP
     selector:
       app: frontendv2
     ports:
       - name: http
         port: 80
         targetPort: 8080

5. Set it so that 50% of the requests go to the original frontend service and the other 50% go to the frontendv2 service:
6. Check the browser again and, if you refresh a few times, you'll see a new front page every second refresh on average:
7. Finally, create a rule where the main page on route "/" is always routed to the new frontendv2 service, but all the other pages use the original frontend service:

Monitoring

1. With live dashboards you can see where the requests are routed and how they respond based on your gateway configurations, in the Backyards UI:

Cleanup

To remove the demo application and Backyards from your cluster, run the following command, which removes all of these components:

kubectl delete ns
hipstershop backyards uninstall -a

Takeaway

Istio's ingress gateway is a perfectly reasonable API gateway implementation to use based on feature set, but its configuration and maintenance are complex, which may not suit the needs of many users. Backyards (now Cisco Service Mesh Manager) increases productivity when working with Istio gateways by combining Istio’s strong feature set with an API Gateway’s user experience.

Want to know more? Get in touch with us, or delve into the details of the latest release. Or just take a look at some of the Istio features that Backyards automates and simplifies for you, and which we've already blogged about.