exchange

A toy "coin exchange". Built as an exercise in Docker, learning Kafka, and systems architecture

Running

To run, you must have Docker, Docker Machine, and Docker Compose.

Clone the repo and then run:

docker-compose up

or run

docker-compose up -d

to run the entire system as a daemon (no log output to STDOUT)

Please wait around 1 minute for the website to be active (how long it takes Kafka to init) Then visit localhost:5001 and enjoy!

Scaling

You can also scale the 3 main services or the Kafka service as needed by doing a

docker-compose scale kafka 4

And replacing kafka and 4 with your service name and count.

This allows for failover protection and high performance load balancing. If scaling the Kafka group, you can also specify topic partitions and replicas in the docker-compose.yml

Usage

Either login with an existing UserID or press "Create new user"
Each user is given $1000 and 100 coins at start
Put in a buy or sell order by specifying the amount of coins you wish to buy/sell and the price
Watch orders come in the order book and have fun.

Architecture

We have 3 services, gateway, risk and match.

gateway is used to host the website and interface with the user through sockets. It is a simple Flask server, and both the site and the server use Socket.IO to communicate
risk is a simple service used to validate if a user can conduct a purchase or a sale.
match is a simple order filler. It does not do partial orders. Instead, it only matches exact orders (Buy for 3@$4 will be matched with a Sell for 3@$4) in order of arrival (FIFO). In addition there are 4 more services that run:
Kafka and ZooKeeper -> Used for the message bus between our three core services.
Redis (2 databases) -> We have a database for both the user data (how much money/coins they have) and the trades that are currently being conducted.

ToDo

This is far from fully featured: