BambangShop Receiver App

Tutorial and Example for Advanced Programming 2024 - Faculty of Computer Science, Universitas Indonesia

About this Project

In this repository, we have provided you a REST (REpresentational State Transfer) API project using Rocket web framework.

This project consists of four modules:

1. controller: this module contains handler functions used to receive request and send responses. In Model-View-Controller (MVC) pattern, this is the Controller part.
2. model: this module contains structs that serve as data containers. In MVC pattern, this is the Model part.
3. service: this module contains structs with business logic methods. In MVC pattern, this is also the Model part.
4. repository: this module contains structs that serve as databases. You can use methods of the struct to get list of objects, or operating an object (create, read, update, delete).

This repository provides a Rocket web framework skeleton that you can work with.

As this is an Observer Design Pattern tutorial repository, you need to implement a feature: Notification. This feature will receive notifications of creation, promotion, and deletion of a product, when this receiver instance is subscribed to a certain product type. The notification will be sent using HTTP POST request, so you need to make the receiver endpoint in this project.

API Documentations

You can download the Postman Collection JSON here: https://ristek.link/AdvProgWeek7Postman

After you download the Postman Collection, you can try the endpoints inside "BambangShop Receiver" folder.

Postman is an installable client that you can use to test web endpoints using HTTP request. You can also make automated functional testing scripts for REST API projects using this client. You can install Postman via this website: https://www.postman.com/downloads/

How to Run in Development Environment

1. Set up environment variables first by creating .env file. Here is the example of .env file:

   ROCKET_PORT=8001
   APP_INSTANCE_ROOT_URL=http://localhost:${ROCKET_PORT}
   APP_PUBLISHER_ROOT_URL=http://localhost:8000
   APP_INSTANCE_NAME=Safira Sudrajat

   Here are the details of each environment variable:

   variable	type	description
   ROCKET_PORT	string	Port number that will be listened by this receiver instance.
   APP_INSTANCE_ROOT_URL	string	URL address where this receiver instance can be accessed.
   APP_PUUBLISHER_ROOT_URL	string	URL address where the publisher instance can be accessed.
   APP_INSTANCE_NAME	string	Name of this receiver instance, will be shown on notifications.

2. Use cargo run to run this app. (You might want to use cargo check if you only need to verify your work without running the app.)

3. To simulate multiple instances of BambangShop Receiver (as the tutorial mandates you to do so), you can open new terminal, then edit ROCKET_PORT in .env file, then execute another cargo run.

   For example, if you want to run 3 (three) instances of BambangShop Receiver at port 8001, 8002, and 8003, you can do these steps:

   • Edit ROCKET_PORT in .env to 8001, then execute cargo run.
   • Open new terminal, edit ROCKET_PORT in .env to 8002, then execute cargo run.
   • Open another new terminal, edit ROCKET_PORT in .env to 8003, then execute cargo run.

Mandatory Checklists (Subscriber)

• [v] Clone https://gitlab.com/ichlaffterlalu/bambangshop-receiver to a new repository.
• STAGE 1: Implement models and repositories
  • [v] Commit: Create Notification model struct.
  • [v] Commit: Create SubscriberRequest model struct.
  • [v] Commit: Create Notification database and Notification repository struct skeleton.
  • [v] Commit: Implement add function in Notification repository.
  • [v] Commit: Implement list_all_as_string function in Notification repository.
  • [v] Write answers of your learning module's "Reflection Subscriber-1" questions in this README.
• STAGE 3: Implement services and controllers
  • [v] Commit: Create Notification service struct skeleton.
  • [v] Commit: Implement subscribe function in Notification service.
  • [v] Commit: Implement subscribe function in Notification controller.
  • [v] Commit: Implement unsubscribe function in Notification service.
  • [v] Commit: Implement unsubscribe function in Notification controller.
  • [v] Commit: Implement receive_notification function in Notification service.
  • [v] Commit: Implement receive function in Notification controller.
  • [v] Commit: Implement list_messages function in Notification service.
  • [v] Commit: Implement list function in Notification controller.
  • [v] Write answers of your learning module's "Reflection Subscriber-2" questions in this README.

Your Reflections

This is the place for you to write reflections:

Mandatory (Subscriber) Reflections

Reflection Subscriber-1

1. In this tutorial, we used RwLock<> to synchronise the use of Vec of Notifications. Explain why it is necessary for this case, and explain why we do not use Mutex<> instead?

Imagine we have a whiteboard (representing the notification list), Mutex<> allow only one person to interact with the board at a time, regardless if they want to write or just want to read the whiteboard, meanwhile RwLock<> allow as many people to read the whiteboard at the same time, meanwhile if a person want to write, they have to wait for everyone to stop reading so the one writting can get exclusive access. Since we look at the notification list more often than we write to it, RwLock is usually faster because it lets all the readers peek simultaneously without blocking each other. We only pay the "wait" cost when someone actually needs to write. Mutex would make even readers wait for each other, slowing things down unnecessarily for reads.

2. In this tutorial, we used lazy_static external library to define Vec and DashMap as a “static” variable. Compared to Java where we can mutate the content of a static variable via a static function, why did not Rust allow us to do so?

Rust is like a very strict parents who really doesn't want us to mess things up, especially when we share toys/data with other people/threads, because changing shared static stuff can cause a data race a nasty bug where multiple threads try to read and write to the same spot at the exact same time without coordination, leading to totally unpredictable results and crashes, java on the other hand has more freedom, it lets us do it because it trust us to be careful, that's why rust makes us use tools like lazy static to set up complex shared data properly, to make sure it's done safely and doesn't cause data races, it's more work upfront but way safer.

Reflection Subscriber-2

1. Have you explored things outside of the steps in the tutorial, for example: src/lib.rs? If not, explain why you did not do so. If yes, explain things that you have learned from those other parts of code.

No, i have read the lib.rs, but i didn't really modify anything as i'm still new to rust and might not know if i break something when i deviate from the tutorial steps.

2. Since you have completed the tutorial by now and have tried to test your notification system by spawning multiple instances of Receiver, explain how Observer pattern eases you to plug in more subscribers. How about spawning more than one instance of Main app, will it still be easy enough to add to the system?

If we have more Receivers (Subscribers) then the Main app just have to add the new Receiver's URL to its list when it subscribes, the notify function doesn't care how many are on the list, therefore no code changes needed on the Main app.

On the other hand if we have more Main app then each Main app would have its own separate subscriber list, which mean they wouldn't share info, and making multiple publishers work together would need a totally different, more complex approach (like a shared database or message queue) to keep the subscriber lists synced up, which makes the code more complicated.

3. Have you tried to make your own Tests, or enhance documentation on your Postman collection? If you have tried those features, tell us whether it is useful for your work (it can be your tutorial work or your Group Project).

No i have not, but i have tried the already made feature from the Postman collection provided, and try some of my variant of it (primarily by changing the port), at the very least i can confidently say that my program run successfully.