Project 1 for CPSC416 Distributed Systems, UBC February 2018
This document explains how we have implemented the BlockArt project, which is specified at http://www.cs.ubc.ca/~bestchai/teaching/cs416_2017w2/project1/index.html
The goal of the project is to implement a platform for a blockchain-based, collaborative art-project. The art project consists of a single global canvas, unto which all participants can issue commands. The main commands a user can issue are draw and delete. In addition, a user can perform a number of queries to the canvas, including ink-level, blockchain-state and more.
For a user to take part in the art-project, it must be connected to a single miner in the ink-mining network. A user connects to a miner using the miner's private key and the miner's network address. Miners are responsible for issuing commands on behalf of connected clients, as well as disseminating and validating operations on a distributed blockchain.
A user can either connect to the system through a web browser, by connecting to the webserver, implemented in webserver.go, or through a Go script that imports the blockartlib library.
The mining network is maintained by the central server (server.go), which takes care of miner registration and handles requests from miners who need more peers. The miners have to send regular heartbeats to the central server, which keeps a list of live miners.
The blockartlib library defines the API for a client (ArtNode) to connect to a miner.
The ArtNode—Miner connection is implemented using remote procedure calls (RPC) over a HTTP/TCP connection.
The blockartlib library allows two types of shapes to be drawn on the cancas, paths and circles.
The shapes are modelled on the SVG format. Blockartlib's SVGParser-object parses user input into an internal point-based representation satisfying the Shapeinterface. As well as arguments specifying the shape itself, we allow the two extra arguments fill and stroke to be set. The shape interface specifies two methods: Area() and XMLString(). These methods are used for translating add/delete commands into operations on the mining network. Finally, the Intersects(shape1, shape2) function is used for checking if two shapes intersect.
