Exercise 1: Our First μ-service: User Activity

Previously on HOMicS -> Exercise 0: Monolith

Context

In our application, we track user activity upon login and logout. This functionality is already implemented in the monolith codebase.

In WebSecurityConfig, you can find two classes CustomAuthenticationSuccessHandler and CustomLogoutSuccessHandler. Those classes implement some Spring Security interfaces to define a strategy used to handle a successful user authentication or logout. In our case, they call the UserActivityService which save the event in database through it UserActivityRepository.

tip you can read more about spring security AuthenticationSuccessHandler in the official documentation.

The front fetches those events for display through an internal API in UserActivityInternalController.

Goal

We are going to create a new service in charge of logging user activities. Let's be creative and call it: 'user-activity'. It will store every user activities in its own database and display the information on a dedicated page. The monolith will call this microservice via API to notify of a successful user login or logout.

user-activity

At your keyboards

Checkout the branch:

    git checkout exercise-1

There is a new folder for the user-activity microservice. You are not going to start from scratch but you will need to implement some of the API.

1.1 - User Activity

[todo 1] - Save a user's activity

In UserActivityApiController, register any activity sent via the new API /user/api/activity.

info You will need to use the @PostMapping with the @RequestBody annotations to extract the right DTO.

warning The @RequestMapping annotation on the class already specifies the URI /user/api.

Checklist:

  1. Run the user-activity project with the following command to access the microservice via localhost:8080/user/userActivity:

    mvn spring-boot:run -pl user-activity

    You should see your microservice up. The User Activity micro tab works but any other tab returns a 404. It's logic since the monolith is the one providing those pages but it isn't up.

  2. Call the api with the following command to log an activity:

    curl -d '{"username":"Jean Bonbeurre", "activityType":"LOGIN", "activityDate":"2019-04-18T15:00:00.000Z"}' -H "content-type: application/json" http://localhost:8080/user/api/activity

  3. Check on the localhost:8080/user/userActivity that you can see the new activity that you just sent.

[todo 2] - Start the monolith

mvn spring-boot:run -pl monolith

error You realize that you have the following error:

2019-12-25 23:20:56.600 ERROR 10837 --- [  restartedMain] o.s.b.d.LoggingFailureAnalysisReporter   : 
***************************
APPLICATION FAILED TO START
***************************
Description:
The Tomcat connector configured to listen on port 8080 failed to start. The port may already be in use or the connector may be misconfigured.
Action:
Verify the connector's configuration, identify and stop any process that's listening on port 8080, or configure this application to listen on another port.

The reason is that the two services are started on the same port. Let's change the port for user-activity.

Open the file application.yaml and complete the TODO 1.1.2 to change the server port to 9001

Checklist :

  1. Restart your two apps :

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

  2. Log in on to the app localhost:8080/mono/login and go to User Activity micro tab. You can see the table for the user activities but it's empty. Weird right, since you just logged in.

question How does the monolith 'talk' with the User microservice?

1.2 - Monolith

[todo 3] - In the monolith app, in the UserActivityService class, edit the post() method to call the microservice using restTemplate.

[todo 4] - Modify the UserActivityService methods addLogin() and addLogout() to send data to the new microservice, using the new post() method.

Checklist :

  1. Restart your two apps:

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

  2. Log on the monolith. Navigate to the User Activity Micro tab and you should see the same table than before with your activities.

[todo 5] - Clean up

As a final step, remove any code related to the user activity in the monolith.

info We took care of the front for you.

Great, you just created your first microservice and connected it to your monolith. Not too bad.

List of TODOs locations

Todo File(s)
1 com.homics.useractivity.controller.UserActivityApiController
2 application.yaml for user-activity
3 com.homics.monolith.service.UserActivityService
4 com.homics.monolith.service.UserActivityService
5 com.homics.monolith.service.UserActivityService / com.homics.monolith.model.UserActivity / com.homics.monolith.controller.UserActivityInternalController

Database

You can access the database console via the following url.

Results

You should see the following screen.

user-activity

question Did you notice the port number after 'localhost' in the URL?

question Did you realize that you can access the User Activity microservice on port 9001 without authentication?

The user navigating on the application can see that we are switching between two ports/applications. We did not copy the authentication on the new microservice, but we could.

Let's see in the next exercise how to centralize the authentication and to have a single entry point in our application.

What's next ? Exercise 2: Gateway