README: Polltron

This is a simple application accompanying a three-part Summa blog post. It uses:

• Ruby 2.0
• Rails 4.0
• Redis

And it's built to be deployed on Heroku. It's not something you should use in the real world but instead it's built to demonstrate how these different tools are used.

Getting started

First, check out this repository. I use the command-line, so it would look like this:

$ git clone git@github.com:cwinters/polltron.git
Cloning into 'polltron'...
remote: Counting objects: 69, done.
remote: Compressing objects: 100% (51/51), done.
remote: Total 69 (delta 7), reused 69 (delta 7)
Receiving objects: 100% (69/69), 15.

Now let Bundler do its work:

$ cd polltron
polltron: $ bundle install
Using rake (10.1.1)
...
Using uglifier (2.4.0)
Using unicorn (4.7.0)
Your bundle is complete!
Use `bundle show [gemname]` to see where a bundled gem is installed.

The exercise has a number of references like this (Tag: v0.0.2). You can advance (or retreat) to that particular point in the exercise by checking out that tag in git:

polltron: $ git co v0.0.2

Redis use

Models

We store a few different types of models in Redis. (Traditionally these might be better done in a relational database but we're using Redis for everything.)

Poll

Key poll.{numeric ID}

Value: STRING; serialized JSON with keys:

• id
• name
• choices: array of numeric IDs

Poll choice

Key: poll_choice.{numeric ID}

Value: STRING; serialized JSON with keys:

• id
• name
• poll (full redis key)

User

Key: user.{numeric ID}

Value: STRING; serialized JSON with keys:

• email
• id
• name

Tracking structures

Poll created

Key: poll_created

Value: ZSET; score is timet when poll created; value is poll.{numeric ID}

User created

Key user_created

Value: ZSET; score is timet of creation, value is user.{numeric ID}

User polls

Key: user.{numeric ID}.polls

Value: ZSET; score is timet of poll creation, value is poll.{numeric ID}

User votes

Key: user.{numeric ID}.votes

Value: ZSET; score is timet of vote, value is poll.{numeric ID}.choices {index}

Vote count by poll

Key: poll.{numeric ID}.vote_count

Value: HASH; key is choice ID, value is count of that choice; additional key TOTAL which is the sum.

Vote by poll

Key: poll.{numeric ID}.votes

Value: ARRAY; value is {timet} poll.{numeric ID}.choices {index}

Vote time

Key: vote_time

Value: ZSET; score is timet of vote, value is poll.{numeric ID}

Vote count

Key: vote_count

Value: ZSET; score is total vote count, value is poll.{numeric ID}