Distributed File System (DFS)

Description:

This project implements a simple Distributed File System (DFS) with a server-client-replica architecture. The system is designed for basic distributed file management, ensuring availability by replicating files across multiple servers.

Features

Main Server functionality:

• User authentication: Login and registration for clients.
• File operations:
  • Upload files to the system.
  • Download files, with automatic fallback to replicas in case of unavailability on the main server.
  • Delete files, ensuring removal from all replicas.
• File listing: Retrieve a list of available files.
• Replica management:
  • Distribute files to replicas for redundancy.
  • Handle requests to fetch files from replicas when needed.

FollowerServer Functionality:

• Connects to the MainServer and sends heartbeat notifications to confirm availability.
• Regularly synchronizes its data with the MainServer.
• If the MainServer becomes unresponsive:
  • Attempts to connect to known replicas.
  • Assumes the role of a server, providing availability and updating other replicas as needed.

Replica functionality:

• Synchronize files with the main server.
• Serve as backup storage for file retrieval when the other ones is unavailable.
• Handle file deletion requests from the main server.

Client functionality:

• Easy-to-use commands for interacting with the DFS:
  • File upload, download, and deletion.
  • Fetch a list of files.

Administration and Access Control:

• For each user, an administrator can assign read (r), write (w), and delete (d) permissions. These permissions determine which actions can be performed on visible files.
• Administrators can create or modify user groups and assign users to these groups.
• Administrators can promote users to administrators, granting them access to management functions.
• In case of need, administrators can remove a user's account from the system.

Requirements

General Requirements:

• Programming Language: C++ with Qt framework.
• Database: SQLite.

Specific Libraries:

• Qt Core and Network modules (e.g., QTcpServer, QTcpSocket).
• Qt SQL module for database integration.

Build and Use:

Building:

1. Individual Builds:
   Navigate to the desired subproject directory (e.g., MainServer, FollowerServer, ReplicaServer, or DFS) and run build.bat to compile the project for that specific part.

2. Build All at Once:
   Alternatively, you can build the entire system at once by using the build.bat script located in the root of the repository. Running this script will:

   • Compile each part of the system (MainServer, FollowerServer, ReplicaServer, and DFS) individually.
   • All binaries will be placed in the build_ninja directory, with separate folders for each subproject, containing the corresponding executable files (MainServer.exe, FollowerServer.exe, ReplicaServer.exe, and DFS.exe).

Running:

1. After building, locate the build_ninja folder in the root directory.
2. Inside the build_ninja folder, you will find individual folders for each subproject.
3. Run the respective executable files (MainServer.exe, FollowerServer.exe, ReplicaServer.exe, or DFS.exe) from their corresponding subfolder.

Usage:

• Start the main server and replicas first to ensure proper system initialization.
• Launch the client application to interact with the DFS.
• After starting the servers, log in to the DFS client application and create a new user.
• Then log in with the credentials admin (username) and !For@each (password).
• Assign the newly created user as an administrator to give them access to management functions.
• For security purposes, delete the old administrator account after the new admin account is set up.
• Once the new administrator is in place, you can grant permissions and provide access to other participants.