Modesty

Modesty is a really simple metrics and a/b testing framework that doesn't really do all that much. It was inspired by assaf's Vanity (github.com/assaf/vanity).

A metric keeps track of things that happen, and ties in and disaggregates many different types of data. Define a metric with:

Modesty.new_metric :foo

Your metric will now be available as Modesty.metrics[:foo]. You can track it with

Modesty.track! :foo`,

You can get a raw count with

Modesty.metrics[:foo].count`.

You can track multiple counts with Modesty.track! :foo, 7, or, if you prefer, Modesty.track! :foo, :count => 7.

Simple, huh?

You can also pass in any sort of data when you track your metric. For example,

Modesty.track! :product_page_viewed, :with => {:product_id => 500, :seller_id => 278}

This provides you with a few more granular methods.

m = Modesty.metrics[:product_page_viewed]
m.unique :product_ids # => number of unique product_ids that were tracked
m.all :product_ids    # => the actual ids that were tracked
m.aggregate_by :product_ids # => a hash of {product_id => tracks for this product id}
m.distribution_by :product_ids # => equivalent to aggregate_by(:product_ids).values.histogram

TODO: submetrics

To save you some hassle, Modesty keeps around a global identity in Modesty.identity. You can set the identity with Modesty.identify! id, where id is either an integer (i.e. the id of the current user) or nil for guests. When the identity is present, all metrics tracked will get a :user parameter passed in. This makes it really easy to call m.unique :users and such, without having to pass it in every time. To override this, just call Modesty.track! :metric, :with => {:user => other_user}.

If you're using Rails, I recommend putting a before_filter on ApplicationController that does something akin to Modesty.identify! viewer.id.

Experiments are really the point of Modesty. With an experiment, you separate your users into experiment groups and track how each group performs on a given set of metrics. Modesty will ensure that

• each group contains roughly the same number of users
• Each user has a consistent experience
• All specified metrics can be disaggregated by experiment group.

Here's how you make an experiment:

Modesty.new_experiment :button_size do |e|
  e.metrics :conversion, :view
  e.alternatives :huge, :medium, :small
end

Then, you can do something like this (in a controller, say)

button_size = Modesty.experiment :button_size do |e|
  e.group :huge do
    9001
  end
  e.group :medium do
    1337
  end
  e.group :small do
    2
  end
end

This code will use Modesty.identity to determine the appropriate experiment group, and run the corresponding block.

All your tracking data will automagically be disaggregated into

Modesty.metrics[:conversion/:button_size/:huge]
Modesty.metrics[:conversion/:button_size/:medium]
Modesty.metrics[:conversion/:button_size/:small]

TODO.

##Datastores and config

Right now there are two datastores available: Redis and a sweet mock Redis for testing. To switch between them, use

Modesty.data = :redis
Modesty.data = :mock

If you need to pass in more options, use

Modesty.set_store :redis, :port => 8888, :host => '123.123.123.1'

By default, Modesty looks in configy/modesty.yml for something like:

datastore:
  type: redis
  port: 6739
  host: localhost

paths:
  experiments: modesty/experiments
  metrics: modesty/metrics

In this, the default setup, Modesty will look for experiments in #{Rails.root}/modesty/experiments, and metrics in #{Rails.root}/modesty/metrics. If no config file is found, or you omit something, Modesty will use these settings. Everything in the datastore: stanza (sans type: redis) will be passed as options to Redis.new.

Have fun!