Kubernetes Ingress for applications with branded links on GKE
While dealing with branded links during my course of work, I kind of wondered how it can be tackled if I were to do it in a Google Kubernetes Engine Cluster. The situation I would imagine that would need to solve is this:
- The application is to be deployed via Helm Chart
- Maybe due to legal/business reasons, it has been arranged such that 1 copy of the application will only 1 customer. So if we have 5 customers, we would need to deploy the above Helm Chart 5 times with different configurations that are accustomed to each customer.
- We don’t want to handle too many clusters as it will cause too much overhead for maintainence and cost of running 1 cluster per customer (we would also need to manage monitoring etc). It would be best to deploy all those applications to 1 single cluster and then have some sort of mechanism to redirect customer to their specific pod on the cluster.
- Each customer will access the application with their own branded link. It has been previously arranged such that each customer can purchase their own domain and by accessing that domain, they should able to access the application deployed on that cluster.
Deploying separate charts with different configurations
As an example, we can try deploying the following application from this repo: https://github.com/hairizuanbinnoorazman/Go_Programming/tree/master/Web/basicHelm
The reason for proposing to test with the following application is that we can alter the environment variable
TARGET within the helm chart to simulate different configurations of the applications. The application will return the value of
TARGET in its response - so by altering it, we can have the same application but its behaviour slightly made different.
We can build the docker image for this and prep it to be used by Google Kubernetes Engine by running the following commands:
# Replace the XXXX with your own project ID docker build -t gcr.io/XXXX/yahoo:v1 . docker push gcr.io/XXXX/yahoo:v1
To change the config file - alter the value of the environment value of
TARGET in the
deployment.yaml file of the helm chart with the
basic-app folder. Once done, we can deploy it via the following command:
# Assume that the environment value of TARGET was changed to yahoo helm upgrade --install yahoo ./basic-app # Assume that the environment value of TARGET was change to lola helm upgrade --install lola ./basic-app
This should hopefully get the application to run. The initial version of the chart sets the replica count to 5 - so maybe this might be too high for an example use case; you might want to adjust it to a lower replica count value.
kubectl get pods
Response of the above command:
NAME READY STATUS RESTARTS AGE lola-basic-app-6957f859cf-4cw98 1/1 Running 0 3h41m lola-basic-app-6957f859cf-85n5d 1/1 Running 0 3h41m lola-basic-app-6957f859cf-gqqjp 1/1 Running 0 3h41m lola-basic-app-6957f859cf-jz5zn 1/1 Running 0 3h41m lola-basic-app-6957f859cf-mnsnm 1/1 Running 0 3h41m yahoo-basic-app-7bfcc945d7-65tkf 1/1 Running 0 4h3m yahoo-basic-app-7bfcc945d7-j2br9 1/1 Running 0 4h3m yahoo-basic-app-7bfcc945d7-pzjlr 1/1 Running 0 4h3m yahoo-basic-app-7bfcc945d7-qljcm 1/1 Running 0 4h3m yahoo-basic-app-7bfcc945d7-snxhf 1/1 Running 0 4h3m
To check that the application is somewhat running properly, we can “exec” into a container and run some commands to make sure it kind of works (don’t forget that the application deployed here allows one to do so. Other production ready applications out there are usually configured to not allow this to improve the security posture of deploying such containerized applications.)
kubectl exec -it yahoo-basic-app-7bfcc945d7-snxhf -- /bin/bash
Once inside the container, we can run the following command:
We would probably get the following response:
root@yahoo-basic-app-7bfcc945d7-snxhf:/home# curl localhost:8080 Hello World: Yahoo!
With that, we can proceed to the next step of externalizing the application.
Single entry point
There many ways to fulfil the above situation. One way is to create 1 load balancer per customer in Google Cloud. Unfortunately, doing that might not be most wise - having 1 load balancer is already above $10-$15 (may vary). The price overhead might be a little high if we are to run it by that approach.
Another approach is to use Kubernetes Ingress - under the hood, it would set up a single Load Balancer and that single load balancer will be used to set up the various incoming traffic (ingress) rules and how to treat each incoming traffic.
You can see an example of such an ingress (We can have multiple ingress definition yaml files - Kubernetes is able to combine them). The following ingress file is used to define 2 branded domains that customers can access.
# Save the file as all-ingress.yaml apiVersion: networking.k8s.io/v1 kind: Ingress metadata: name: test-ingress spec: rules: - host: yahoo.example.com http: paths: - path: / pathType: Prefix backend: service: name: yahoo-basic-app port: number: 8080 - host: lola.example.com http: paths: - path: / pathType: Prefix backend: service: name: lola-basic-app port: number: 8080
We get the services of where to send the traffic from ingress by inquiring the services on Kubernetes
kubectl get services
Response for the above command:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.116.0.1 <none> 443/TCP 4h55m lola-basic-app ClusterIP 10.116.1.211 <none> 8080/TCP 3h53m yahoo-basic-app ClusterIP 10.116.6.9 <none> 8080/TCP 4h50m
We will apply the ingress rules to the Kubernetes cluster by running the following command
kubectl apply -f all-ingress.yaml
Once applied, we can check the state of ingress.
kubectl get ingress
Note that for GKE, it will take above 2-5 minutes for IP to come up on Address field. Under the hood, GKE actually contacts Google APIs to create 1 load balancer on our behalf and then apply the rules to said Load Balancer. It would then attempt and work to ensure that ingress rules are synced up to the load balancer.
NAME CLASS HOSTS ADDRESS PORTS AGE test-ingress <none> yahoo.example.com,lola.example.com 126.96.36.199 80 175m
In order to test this out, we can then add the address of the ip address that was assigned for this to our
/etc/hosts file (not sure if there is anything similar for windows. We’re trying to assign an ipaddress to a domain name)
188.8.131.52 yahoo.example.com 184.108.40.206 lola.example.com
Append the above to the mentioned file. Be careful when handling this file, other programmes could have added entries to the file and manipulating the
/etc/hosts file without any care may cause issues with said programmes. You can try avoiding this by making a backup of the
/etc/hosts file just in case. If things go south, you can replace the altered
/etc/hosts with the backup file.
We can now run curl on domains
lola.example.com and it should be able to return an expected response from the deployed application
curl yahoo.example.com # Response # Hello World: Yahoo!
curl lola.example.com # Response # Hello World: Lola!