Statisfy

This gem allows you to easily create performant statistics for your ActiveRecord models without having to write and run complex SQL queries.

By leveraging the power of Redis, Statisfy elegantly manages counters in the background so that you can use them with ease.

Installation

Add this line to your application's Gemfile:

gem 'statisfy'

Execute

$ bundle install

Then add the following to a config/initializers/statisfy.rb file:

Statisfy.configure do |config|
  # This is the Redis client that will be used to store counters
  config.redis_client = Redis.new

  # If you want to use Sidekiq to update counters in the background
  # This is optional, but recommended for performance reasons
  # Anything you add to this block will be executed in the context of the
  # Sidekiq worker that updates the counters
  #
  config.append_to_counters = ->(_) { include Sidekiq::Worker }

  # This allows you to define the default scopes for your counters
  # This is simply to avoid having to define the same scopes over and over
  # again for each counter
  config.default_scopes = -> { [subject.organisation, subject.department] }
end

# The following is important because it ensures that all counters are loaded
# and can start listening events without having to require them manually.
Rails.application.config.after_initialize do

  # You can put your counters anywhere you want, as long as they are loaded
  Dir[Rails.root.join("app/stats/counters/**/*.rb")].each { |file| require file }
end

Simple usage

Basic counter

This will simply increment the counter every time a User is created.

# Define a class, and include the Statisfy::Counter module
# You can put this class anywhere you want, as long as it is loaded by the initializer
# See the Installation section for more details
class UsersCreated
  include Statisfy::Counter

  count every: :user_created
end

# Anytime a user is created, the counter will be incremented
User.create(name: "John Doe")

# And then get the count like this:
UsersCreated.value
# => 1

# You can also get the count for a specific month
UsersCreated.value(month: Time.now)

# Or get a graph of values grouped by month
# By default it returns the last 24 months
UsersCreated.values_grouped_by_month(stop_at: Time.now.last_month.end_of_month, start_at: Time.now.last_year)
# => 
# {
#   "2023/01", value: 766,
#   "2023/02", value: 1246,
#   ... 
# }

If you prefer you can also include Statisfy::Model in your model and define the counter directly on the model. In this case you'll have to prefix APIs with statisfy_ to avoid conflicts with ActiveRecord methods.

You'll also need to specify the :as option to give a name to your counter which will be used to access the value.

class User < ApplicationRecord
  include Statisfy::Model

  statisfy_count every: :user_created, as: :number_of_users_created
  statisfy_aggregate every: :user_update, as: :average_salary, value: -> { salary }
end

User.create(name: "John Doe", salary: 1000)
User.create(name: "John Troe", salary: 2000)

# And then get the count like this:
User.number_of_users_created.value
# => 2

User.average_salary.value
# => 1500

Scoped counter

Imagine you have a User model that belongs to an Organisation and you want to count the number of users created per organisation.

class UsersCreated
  include Statisfy::Counter

  count every: :user_created,
        scopes: -> { [user.organisation] }
end

# This will increment the counter for the organisation of the user (and also the global one)
User.create(name: "John Doe", organisation: Organisation.first)

# And then get the count like this:
UsersCreated.value(scope: Organisation.first)
# => 1

# Or get a graph of values grouped by month
UsersCreated.values_grouped_by_month(scope: Organisation.first)

Aggregation based statistics

This is useful when you want to get an average or sum of a value.

class AverageUserSalary
  include Statisfy::Aggregate

  aggregate every: :user_created,
            value: -> { user.salary }
end

User.create(name: "John Doe", salary: 1000)
User.create(name: "Jane Doe", salary: 2000)


# This will return the average salary of all users
AverageUserSalary.value
# => 1500

# This will return the sum of all salaries
AverageUserSalary.sum
# => 3000

# You can also get the average salary for a specific month, scope, etc
AverageUserSalary.value(month: Time.now, scope: Organisation.first)

API

count

This method is used to define a counter.

Note that every lambda option is executed in the context of the counter instance. You can access the model instance under the model instance name. For instance user for a User model.

Parameter	Type	Description
every	Array	The event(s) that will trigger the counter. model_(created/updated/destroyed). The model is deduced from the event name. :user_created will catch every User.create!
scopes	lambda, optional	Array of scopes to take into account. For instance, if a model Post has_many authors, then setting -> { post.authors } will tell you how many authors wrote a post
if	lambda, optional	Boolean. If it returns false, the counter will not be incremented. You have access to your instance .previous_changes which allows you to increment only upon certain changes.
if_async	lambda, optional	Boolean. Similar to if, but executed asynchronously. Allows to not slow down INSERT or UPDATE statements. Useful if your if calls complex model relationships
decrement_if	lambda, optional	Boolean. If it returns true, then the counter will be decremented instead of incremented
uniq_by	lambda, optional	Won't count the same value twice. By default it is uniq on the id. Example use case: if a Post is written by an author_id, you could set -> { post.author_id} to know how many authors wrote an article this month
decrement_on_destroy	Boolean, optional	Default is true. The counter will be decremented when the model instance is destroyed.
date_override	DateTime, optional	Default is instance.created_at.

aggregate

This method is used to define an aggregate counter.

Note that every lambda option is executed in the context of the counter instance. You can access the model instance under the model instance name. For instance user for a User model.

An aggregate counter has the same options as a basic counter, but also has the following options:

Parameter	Type	Description
value	lambda	The value to aggregate that will be used to compute the average or sum.

Class methods

.values_grouped_by_month

This method returns a hash containing the months and the values of the counter for that month. If you want to use this method outside of a counter, you can include include Statisfy::Monthly which contains this method only.

Parameter	Type	Description
scope	Object, optional	The scope of the counter. See scope option above
start_at	Date, optional	The date from which you want to start counting. If not provided, counts from the beginning.
stop_at	Date, optional	The date at which you want to stop counting. If not provided, counts up to the current date.

Returns

{
  "2023/01", value: 766,
  "2023/02", value: 1246,
  ...
}

.value

This method returns the value of the counter.

Parameter	Type	Description
scope	ActiveRecord instance, optional	The scope of the counter. See scope option above
month	Date, optional	The month for which you want to get the value. If not provided, returns the value for the current month.

.sum

This method returns the sum of the values of the counter. /!\ This method is only available for counters that use the Statisfy::Aggregate module.

Parameter	Type	Description
scope	ActiveRecord instance, optional	The scope of the counter. See scope option above
month	Date, optional	The month for which you want to get the value. If not provided, returns the value for the current month.

.average

This method returns the average of the values of the counter. /!\ This method is only available for counters that use the Statisfy::Aggregate module.

Parameter	Type	Description
scope	ActiveRecord instance, optional	The scope of the counter. See scope option above
month	Date, optional	The month for which you want to get the value. If not provided, returns the value for the current month.

Initializing a counter

If you want to count on a model with existing data, you'll need to initialize the counter. Initializing a counter is done by manually triggering an increment of counters. Basically it's a matter of doing this:

# Given a User class
class User < ActiveRecord::Base
end

# And a counter
class UsersCreated
  include Statisfy::Counter

  count every: :user_created
end

# You can initialize the counter like this
User.all.find_each do |user|
  UsersCreated.trigger_with(user)
end

Users created in the meantime and in the future will be automatically counted anyway.

Initializing scoped counters

If your data is scoped with some of your model associations, don't forget to include the associated models to speed up the initialization:

class User < ActiveRecord::Base
  belongs_to :organisation
  belongs_to :department
end

class UsersCreated
  include Statisfy::Counter

  count every: :user_created,
        scopes: -> { [user.organisation, user.department] }
end

User.all.includes(:organisation, :department).find_each do |user|
  UsersCreated.trigger_with(user)
end

Initializing counters with conditions

If you need to increment only some instances, the if option of your counter will automatically bypass the instances not matching the condition.

But if your counter requires conditions only present during updates, like coming from .previous_changes, since this data is not available during initialization, you'll need to add that condition to the request manually, and also skip validations.

For instance, consider the following counter:

class NumberOfActiveUsers
  include Statisfy::Counter

  count every: :user_created,
        if: -> { user.previous_changes[:status].present? && user.status == "active" }
end

You'll need to initialize the counter like this:

# Retrieve all users matching the condition
User.where(status: "active").find_each do |user|
  # Skip validations to avoid running the `if` condition
  # This is safe because we know that all given users match the condition
  NumberOfActiveUsers.trigger_with(user, skip_validation: true)
end

Development

After checking out the repo, run bundle and the bundle rake to run the test suite.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/Michaelvilleneuve/statisfy.

License

The gem is available as open source under the terms of the MIT License.