Content table:

• Intro
• Building for local development
• Building docker containers
• Docker hub image
• Public deploy
• HTTP API
• Code structure

Intro

Results is a purely academic exercise developed as a technical test.

It is quite simple, takes a list of results from a CSV file, parses it and exposes a REST endpoint that allows getting division-seasons pairs and the results for every given division-season.

The main idea was to keep it simple to allow an easy review of the code, it is not production ready, it lacks code instrumentation and more sophisticated orchestration.

Building for local development

In order to build the project locally, you should have Elixir ~> 1.8 installed. mix.lock file was attached to the project to guarantee dependencies will remain stable for later builds, feel free to remove it.

$ git clone https://github.com/cristiandavidgm/results_exercise.git
$ cd results_exercise
$ mix deps.get
$ mix deps.compile
$ mix compile
$ iex -S mix

then go to http://127.0.0.1:8880/v1/json/leagues and voilà

Building docker containers

Two Docker files are shipped with the project:

• ./Dockerfile will build a release of the project and pack it into a docker container using the latest tag.
• ./haproxy/Dockerfile will just build an image using the provided configuration file in ./haproxy/haproxy.cfg

There is a very simple docker-compose file that will:

• Create three containers of the result app.
• Create a container of HAproxy that will distribute the load between the tree app nodes.

The stack is quite simple, there is not dynamic done configuration, just and HAproxy and 3 app nodes.

To build the docker image:

$ make build

Then you should have two images of the app:

$ docker image ls
REPOSITORY  TAG IMAGE ID  CREATED  SIZE
results 0.0.1-85bddd6 a0c275e205a3  48 seconds ago 56.9MB
results latest  a0c275e205a3  48 seconds ago 56.9MB
<none>  <none>  99381b43a570  About a minute ago 170MB
alpine  3.8 dac705114996  5 days ago 4.41MB
elixir  1.8.0-alpine  9b74d9066f05  5 weeks ago  87.6MB

The docker-compose file uses "results-latest" image, run:

$ docker-compose up --build

And it will pull HAproxy form docker hub, create a docker image with the provided configuration and start 1 HAproxy in front of 3 app nodes.

go to http://127.0.0.1:8881/v1/json/leagues

Docker hub image

A public docker image was pushed to https://hub.docker.com/r/cristiandavidgm/results and can be pulled using:

$ docker pull cristiandavidgm/results

Also, a different docker-compose file is provided, that file will use the public image so nothing hs to be built, run:

$ docker-compose -f docker-compose-public-image.yml up --build

Public deploy

The app was deployed to Linode using a nanode with Centos 7 and is available at:

http://li294-74.members.linode.com:8881/v1/json/leagues

Feel free to test it, try to not DDOS my server, it is just a Nanode 1GB: 1 CPU, 25GB Storage, 1GB RAM

HTTP API

Results app provides 2 endpoints:

• /v1/[protocol]/leagues
  • Returns a list of league-season pairs for which results are available
• /v1/[protocol]/results?league=[league]&season=[season]
  • Returns all results related to the league-season pair requested inthe query params.

where protocol can be "json" or "proto", i.e:

• /v1/json/leagues
  • will return a list of league-season pairs in json format
• /v1/proto/leagues
  • will return a list of league-season pairs in Protocol Buffer format
• /v1/json/results?league=D1&season=201617
  • will return a list of results associated with leage D1 season 201617 in json format
• /v1/proto/results?league=D1&season=201617
  • will return a list of results associated with leage D1 season 201617 in Protocol Buffer

Code structure

Results codebase is very simple:

• config/
  • config.exs -> Contains only the config for maru framework
• haproxy/
  • Dockerfile -> To build HAproxy docker image
  • haproxy.cfg -> very specific config to run 3 app nodes behind haproxy
• lib/
  • results/
    • Results.Exprotobuf.Data.ex -> Uses exprotobuf library to parse the provided proto file and create the necessary structures to provide Protocol Buffer responses.
    • db_loader.exs -> Defines a task that will take and parse the provided CSV file and then will insert every row into de app db module
    • http_server.ex -> defines the HTTP interface, the is no logic here, just adapters.
    • league_season.ex -> data structure for league and seasson pairs
    • league_season_db.ex -> Core module, it uses ETS tables to store the results.
    • result.ex -> data structure for results
    • results_api.ex -> This is the main module, all interactions within the app should be made through this module, accessing the DB directly is highly discouraged
    • supervisor.ex -> The one and only supervisor
    • util.ex -> where I place funs that might be common to multiple modules .
  • results.ex -> Application module
• priv/
  • Data.csv -> CSV file with the results for evey league-season pair.
  • results.proto -> Defines Protocol buffer messages format.
• rel/ -> created by "mix release.init", used mostly to configure different parameters for the stacks.
• test/ -> unit tests files.