Scriba: Jot down your ideas, share them with the world

A collaborative real-time editor written in C++ using Qt GUI framework.
It is based on a distributed data structure called Conflict-free Replicated Data Type (CRDT) and implements, in particular, LSEQ strategy.

Motivation

Project developed in the context of Programmazione di Sistema (Operating System Design and Programming) course at Politecnico di Torino. Main features include:

• Reliability
  • Open files are saved every 5 seconds on the database to avoid file loss in case of server crash
  • If the server crashes, the user is kicked out of the application, no risk of losing work done
• Scalability
  • No CRDT data structure in the server, symbols stored unsorted to avoid overload of CRDT algorithm (performed only on clients)
  • Data (user information, images, files) stored in MongoDB: easy replication and sharding
• Security
  • TLS employed through QSslSocket
  • Users’ password hashed before being stored in database using argon2 hash function (through Libsodium library)
• Deployability
  • Docker used to easily deploy server and database, without manual dependencies handling
  • Separate containers for server and database, to allow independent replication and balancing of resources

Read project_requirements.pdf (Italian only) for a detailed description of the requirements.

Installation

Qt libraries need to be installed locally (take a look at https://doc.qt.io/qt-5/gettingstarted.html) to build and run the client application. Two options are available:

• Starting from the root folder of the project and using make. In Linux it can be achieved as follows:

mkdir build && cd build
qmake ../Client/Client.pro -spec linux-g++ CONFIG+=debug CONFIG+=qml_debug
/usr/bin/make -f Makefile qmake_all
/usr/bin/make

• Using Qt Creator: just import the project and run it.

Nothing is required for the server since it can be launched directly in the Docker container.

Usage

Server

To start the server and MongoDB containers, that will be listening respectively on port 1500 and 27017:

bash docker-start.sh

Client

The client application, that will attempt to connect to localhost:1500, can be run with the command:

./build/Client

To use a custom address and port:

./build/Client <ip_addr> <port_number>

Authors

• Enrico Loparco - [email protected]
• Giuseppe Pastore - [email protected]

License

MIT