Exercise 2 : Gateway

Previously on HOMicS -> Exercise 1: User Activity

Context

In the previous schema, you might have realized that there is a flaw. We don't have any authentication for the micro-service.

What happens if you connect directly to the user-activity microservice?

Well you can access directly user-activity. The login page is skipped and the data is accessible! Oopsy, not great at all.

We could duplicate all the security code in the new microservice. But it's not a scalable approach, we'd have to add it in all future microservices. And the services will be loosely coupled. This is where a Gateway becomes handy.

A gateway is a service that provides a single-entry point for certain groups of microservices. Any requests to our application will go through the gateway, that will handle routing to our different services.

Goal

Create the Gateway microservice responsible for all authentication and redirection. It's going to handle the authentication and redirect to the monolith or the user-activity microservice.

Everything has been implemented in other microservices. You only need to edit the gateway.

At your keyboard

Checkout the branch:

git checkout exercise-2

There is a new folder for the gateway microservice. You won't have to start from scratch, but you will need to implement some parts.

Start the gateway and the two other services monolith and user-activity in you IDE.

# gateway
mvn spring-boot:run -pl gateway
# monolith
mvn spring-boot:run -pl monolith
# user-activity
mvn spring-boot:run -pl user-activity

Browse the different pages. You'll realize that all pages return a 404 error. That's because there's no routing in our application.

2 - Gateway

[todo 1] - Application.yaml

There won't be any database for the gateway since it's not holding any data. It's going to be running on port 8080.

We are using ZUUL developed by Netflix. It's an edge service that provides dynamic routing, monitoring, resiliency, security, among other things. Spring integrated it in Spring Cloud.

You will need to set it up in your application.yaml.

zuul documentation is available here

To help you with the configuration in your yml file, here is an example:

zuul:
  routes:
    testservice:
      path: /test/**
      url: http://example.com/test/

[todo 2] - Enable Zuul

Checkout the second todo to enable the Zuul Routing.

Checklist :

1. Since the routing is done and should be working, start your three apps, if they aren't already up:

   # gateway
   mvn spring-boot:run -pl gateway
   # monolith
   mvn spring-boot:run -pl monolith
   # user-activity
   mvn spring-boot:run -pl user-activity
   

2. Check that when login in, you see your articles as well as all other pages under the same port: 8080.

What happens if you try to checkout a shopping cart?

It doesn't work because the monolith doesn't know your user. Let's add it to our context in the next step.

[todo 3] - Logged user information

Last but not least, you need to add the logged user to the headers so all micro services will be able to retrieve the connected user.

Open AddUserFilter and implement the run method so it adds the username into the request context.

Checklist :

1. To check that the gateway is well implemented, launch all the applications:

   # Run monolith project
   mvn spring-boot:run -pl monolith
   
   # Run user-activity project
   mvn spring-boot:run -pl user-activity
   
   # Run Gateway project
   mvn spring-boot:run -pl gateway
   

2. Access the HOMicS MarketPlace. You should arrive on the gateway. After login in, you should be directly redirected to the monolith. You can note that the port is still 8080. You should also be able to access the user-activity microservice on the User Activity micro tab.

Since the Gateway is running on port 8080, the port for the monolith has been changed to 8090.

List of TODOs

Monolith database

You can access the monolith database console via the following url.

Results

You can still access the other services directly on each port 8090 and 9001. In practice, you will block those ports from the outside via a firewall.

Well done! Let's continue on to the next step, with a new microservices.

What's next ? Exercise 3: Stats