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)

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

RwLock vs Mutex

Read-write Lock (RwLock) allows multiple threads to read the notification, which is impossible with Mutex. This allows multiple API requests to view notifications concurrently without blocking each other.

Static variables in Rust vs Java

Static variables in Rust guarantess Memory Safety and thread safety during compile time. Unlike Java, Rust's approach doesn't allow static mutability as it might cause potential data races.

Reflection Subscriber-2

Exploration

I explored things outside the tutorial. Parts in which I find amusing a as follows:

• Configuration management is done in the app config struct and lazy static pattern with the goal of a thread-asfe singleton configuration.
• Error handling is provided by tje custom error response pattern in lib.rs
• REQWEST_CLIENT is a global which create shared resources to prevent creation of resources in every request.

Observer Pattern and Multiple Subscribers

The Observer pattern significantly simplifies adding more subscribers, which are:

1. Publishers and subscribers have no direct dependencies on each other as they only know about the notification format.

2. New subscribers can join or leave at runtime without requiring any code changes to the publisher.

3. All notification uses the same HTTP endpoint format, making it easy to add more instances.

Testing and Documentation

I've done several tests, one of which is a test on my CTF question. It helps me develop things quickly and ensure that my program run as intended, which in case. The feature environment variables helps alot in testing both local and remote url. By defining a base url, we can switch url without having to change every base url in each of the tests in the collection.