rust-multi-db-tenant

A Rust application demonstrating dynamic multi-database (multi-tenant) handling, built using the high-performance Actix-Web framework. This project shows how to:

• Dynamically select a MongoDB database based on an HTTP request header (_db).
• Cache and flush database connections after a specified time period (15 minutes of idle time).
• Structure Rust code in a modular way for ease of maintenance and scalability.

Table of Contents

1. Overview
2. Key Features
3. Project Structure
4. How It Works
   • Multiple Database Handling
   • Database Flushing
5. Setup and Usage
   • Prerequisites
   • Installation
   • Running the Application
6. API Endpoints
   • User Module
   • Todo Module
7. License

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Overview

This example demonstrates how to build a multi-tenant CRUD REST API in Rust. Tenants (databases) are chosen dynamically at runtime via an HTTP request header. This allows you to route multiple clients (or tenants) to separate databases without duplicating code or spinning up multiple servers.

Key Features

• Dynamic Database Selection: The _db header determines which MongoDB database to use for each request.
• Caching with TTL: Uses moka to cache database connections and automatically remove them after 15 minutes of inactivity.
• Modular Architecture: Separate modules for user and todo data models, each with its own router, handler, model, service, and error definitions.
• Async MongoDB Driver: Non-blocking, highly performant database interactions.
• Separation of Concerns: Services return standard Rust Result types, while handlers map those results to HTTP responses. This design makes the code more testable and maintainable.

Project Structure

rust-multi-db-tenant/
├── Cargo.toml
├── .env
└── src
    ├── main.rs
    ├── db.rs
    ├── routes
    │   └── mod.rs
    ├── user
    │   ├── mod.rs
    │   ├── user_router.rs
    │   ├── user_handler.rs
    │   ├── user_model.rs
    │   ├── user_service.rs
    │   └── user_errors.rs
    └── todo
        ├── mod.rs
        ├── todo_router.rs
        ├── todo_handler.rs
        ├── todo_model.rs
        ├── todo_service.rs
        └── todo_errors.rs

Highlights:

• src/db.rs: Manages database connectivity and caching logic.
• src/routes/mod.rs: Central place for registering all module routes.
• src/user/ and src/todo/: Each module has its own routing, handlers, models, services, and error definitions.

How It Works

Multiple Database Handling

1. Header-based DB Selection: Each HTTP request can include a header named _db.
2. Cache Lookup: If the requested database (e.g., "tenant1_db") is in the cache, reuse the existing client. Otherwise, create a new Database instance.
3. Separate Collections: Each database can have its own users, todos, etc., collections.

Database Flushing

• Moka Cache: The project uses moka::future::Cache with a time-to-idle (time_to_idle) set to 15 minutes.
• Idle Expiration: If no requests are made for a particular database within 15 minutes, its entry automatically expires from the cache. This frees up memory and ensures inactive tenants don’t linger.

Setup and Usage

Prerequisites

• Rust (Edition 2021 or newer)
• Cargo (bundled with Rust)
• MongoDB running locally or accessible via network

Installation

1. Clone the repo:

   git clone https://github.com/yourusername/rust-multi-db-tenant.git
   cd rust-multi-db-tenant

2. Configure environment:

   • Create a .env file in the project root (if not present):

     MONGODB_URI=mongodb://localhost:27017

   • You can also modify the TTL in db.rs if needed.

3. Install dependencies:

   cargo build

Running the Application

cargo run

The server will start on 127.0.0.1:8080 by default.

API Endpoints

User Module

• Create User:
  POST /users

  curl -X POST \
       -H "Content-Type: application/json" \
       -H "_db: tenant1_db" \
       -d '{"name":"Alice","email":"alice@example.com","password":"password123"}' \
       http://127.0.0.1:8080/users

• Get All Users:
  GET /users

  curl -H "_db: tenant1_db" http://127.0.0.1:8080/users

• Get User by ID:
  GET /users/{id}

  curl -H "_db: tenant1_db" http://127.0.0.1:8080/users/63f2a...

• Update User:
  PUT /users/{id}

  curl -X PUT \
       -H "Content-Type: application/json" \
       -H "_db: tenant1_db" \
       -d '{"name":"Alice Updated","email":"alice@newdomain.com","password":"NewPass"}' \
       http://127.0.0.1:8080/users/63f2a...

• Delete User:
  DELETE /users/{id}

  curl -X DELETE \
       -H "_db: tenant1_db" \
       http://127.0.0.1:8080/users/63f2a...

Todo Module

• Create Todo:
  POST /todos

  curl -X POST \
       -H "Content-Type: application/json" \
       -H "_db: tenant1_db" \
       -d '{"title":"Buy groceries","description":"Milk, Eggs, Bread","completed":false,"user_id":"63f2a..."}' \
       http://127.0.0.1:8080/todos

• Get All Todos:
  GET /todos

  curl -H "_db: tenant1_db" http://127.0.0.1:8080/todos

• Get Todo by ID:
  GET /todos/{id}

  curl -H "_db: tenant1_db" http://127.0.0.1:8080/todos/63f2a...

• Update Todo:
  PUT /todos/{id}

  curl -X PUT \
       -H "Content-Type: application/json" \
       -H "_db: tenant1_db" \
       -d '{"title":"Buy more groceries","description":"Add cereal","completed":false,"user_id":"63f2a..."}' \
       http://127.0.0.1:8080/todos/63f2a...

• Delete Todo:
  DELETE /todos/{id}

  curl -X DELETE \
       -H "_db: tenant1_db" \
       http://127.0.0.1:8080/todos/63f2a...

License

This project is licensed under the MIT License - see the LICENSE file for details.

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Feel free to open a Pull Request if you have any improvements or to file an Issue if you encounter any problems. Happy coding!