The application contained in this repository consists of an nginx loadbalancer container, one or more web application containers, a redis container and a mysql container.

1. Client makes an HTTP request to 127.0.0.1:8083
2. Docker directs tcp/8083 to nginxlb tcp/4000
3. nginxlb resolves DNS hostname 'webapp' to internal network IP
4. nginxlb directs tcp/4000 to webapp tcp/5000
5. webapp flask application receives traffic on tcp/5000 and performs function based on url
6. /player/create creates a row in mysql and a record in redis
7. /player/get reads from redis and mysql
8. Redis request is returned to webapp
9. MySQL request is returned to webapp
10. webapp request is returned to nginxlb
11. nginxlb request is returned to client

Purpose: This container provides a frontend interface for webtraffic. The nginx proxy will forward the request on tcp port 8083 to the internal inteface of the web application container on port 5000. The nginx loadbalancer will query DNS records in a round-robin mechanism to resolve the alias of 'webapp' set by docker-compose to an internal IP of one of the webapp containers. nginx listens internally on tcp port 4000 and is directed to port 8083 externally by docker which then presents the port to the host operating system on localhost:8083.

Purpose: This container hosts the python flask application on port 5000. It will retrieve environment variables passed from the start.sh script to docker-compose relating to MySQL and Redis authentication details. After creating a connection to these services it will listen on port 5000 to incoming traffic and respond depending on the endpoint url. This is currently /player/create or /player/get. In the event of there being a mismatch between redis and mysql in relation to gold, the app will update mysql with a syncronisation update which could be done asyncronously.

Purpose: Redis is an in-memory cache and can be used to store and update frequently used data. The reason to use redis over mysql is to optimise latency when looking up specific records rather than request the lookup via a relational database. The redis container allows for TTL of records and so infreqently used data can be purged from memory increasing accuracy.

Purpose: MySQL is a relational database which stores information relating to the player such as player name and player gold. When a player is created a row is created in the gamesample database and player table to store for future lookups. The gold is initially set to 0 but can be updated via the webapp.

To install this sample application please follow the instructions below:

Ensure that docker is running and docker-compose 2.0 are installed

git clone https://github.com/dmccue/gamesample.git && cd gamesample

To run the stack please run:

./start.sh <number of webapp containers>

Wait for the stack to create and display output from the nginxlb and webapp containers

In an alternative window type:

./test.sh

You should see the responses to curl commands displayed in the terminal

In an alternative window type:

./stop.sh

### AWS Architecture - FARGATE