Mongoid History

Mongoid History tracks historical changes for any document, including embedded ones. It achieves this by storing all history tracks in a single collection that you define. Embedded documents are referenced by storing an association path, which is an array of document_name and document_id fields starting from the top most parent document and down to the embedded document that should track history.

This gem also implements multi-user undo, which allows users to undo any history change in any order. Undoing a document also creates a new history track. This is great for auditing and preventing vandalism, but is probably not suitable for use cases such as a wiki (but we won't stop you either).

Version Support

Mongoid History supports the following dependency versions:

• Ruby 2.3+
• Mongoid 3.1+
• Recent JRuby versions

Earlier Ruby versions may work but are untested.

Install

gem 'mongoid-history'

Usage

Create a history tracker

Create a new class to track histories. All histories are stored in this tracker. The name of the class can be anything you like. The only requirement is that it includes Mongoid::History::Tracker

# app/models/history_tracker.rb
class HistoryTracker
  include Mongoid::History::Tracker
end

Set default tracker class name (optional)

Mongoid::History will use the first loaded class to include Mongoid::History::Tracker as the default history tracker. If you are using multiple Tracker classes, you should set a global default in a Rails initializer:

# config/initializers/mongoid_history.rb
# initializer for mongoid-history
# assuming HistoryTracker is your tracker class
Mongoid::History.tracker_class_name = :history_tracker

Create trackable classes and objects

class Post
  include Mongoid::Document
  include Mongoid::Timestamps

  # history tracking all Post documents
  # note: tracking will not work until #track_history is invoked
  include Mongoid::History::Trackable

  field           :title
  field           :body
  field           :rating
  embeds_many     :comments

  # telling Mongoid::History how you want to track changes
  # dynamic fields will be tracked automatically (for MongoId 4.0+ you should include Mongoid::Attributes::Dynamic to your model)
  track_history   :on => [:title, :body],       # track title and body fields only, default is :all
                  :modifier_field => :modifier, # adds "belongs_to :modifier" to track who made the change, default is :modifier, set to nil to not create modifier_field
                  :modifier_field_inverse_of => :nil, # adds an ":inverse_of" option to the "belongs_to :modifier" relation, default is not set
                  :modifier_field_optional => true, # marks the modifier relationship as optional (requires Mongoid 6 or higher)
                  :version_field => :version,   # adds "field :version, :type => Integer" to track current version, default is :version
                  :track_create  => true,       # track document creation, default is true
                  :track_update  => true,       # track document updates, default is true
                  :track_destroy => true,       # track document destruction, default is true
                  :track_blank_changes => false # track changes from blank? to blank?, default is false
end

class Comment
  include Mongoid::Document
  include Mongoid::Timestamps

  # declare that we want to track comments
  include Mongoid::History::Trackable

  field             :title
  field             :body
  embedded_in       :post, :inverse_of => :comments

  # track title and body for all comments, scope it to post (the parent)
  # also track creation and destruction
  track_history     :on => [:title, :body], :scope => :post, :track_create => true, :track_destroy => true

  # For embedded polymorphic relations, specify an array of model names or its polymorphic name
  # e.g. :scope => [:post, :image, :video]
  #      :scope => :commentable

end

# the modifier class
class User
  include Mongoid::Document
  include Mongoid::Timestamps

  field             :name
end

user = User.create(:name => "Aaron")
post = Post.create(:title => "Test", :body => "Post", :modifier => user)
comment = post.comments.create(:title => "test", :body => "comment", :modifier => user)
comment.history_tracks.count # should be 1

comment.update_attributes(:title => "Test 2")
comment.history_tracks.count # should be 2

track = comment.history_tracks.last

track.undo! user # comment title should be "Test"

track.redo! user # comment title should be "Test 2"

# undo comment to version 1 without save
comment.undo nil, from: 1, to: comment.version

# undo last change
comment.undo! user

# undo versions 1 - 4
comment.undo! user, :from => 4, :to => 1

# undo last 3 versions
comment.undo! user, :last => 3

# redo versions 1 - 4
comment.redo! user, :from => 1, :to => 4

# redo last 3 versions
comment.redo! user, :last => 3

# redo version 1
comment.redo! user, 1

# delete post
post.destroy

# undelete post
post.undo! user

# disable tracking for comments within a block
Comment.disable_tracking do
  comment.update_attributes(:title => "Test 3")
end

# disable tracking for comments by default
Comment.disable_tracking!

# enable tracking for comments within a block
Comment.enable_tracking do
  comment.update_attributes(:title => "Test 3")
end

# renable tracking for comments by default
Comment.enable_tracking!

# globally disable all history tracking within a block
Mongoid::History.disable do
  comment.update_attributes(:title => "Test 3")
  user.update_attributes(:name => "Eddie Van Halen")
end

# globally disable all history tracking by default
Mongoid::History.disable!

# globally enable all history tracking within a block
Mongoid::History.enable do
  comment.update_attributes(:title => "Test 3")
  user.update_attributes(:name => "Eddie Van Halen")
end

# globally renable all history tracking by default
Mongoid::History.enable!

You may want to track changes on all fields.

class Post
  include Mongoid::Document
  include Mongoid::History::Trackable

  field           :title
  field           :body
  field           :rating

  track_history   :on => [:fields] # all fields will be tracked
end

You can also track changes on all embedded relations.

class Post
  include Mongoid::Document
  include Mongoid::History::Trackable

  embeds_many :comments
  embeds_one  :content

  track_history   :on => [:embedded_relations] # all embedded relations will be tracked
end

Include embedded objects attributes in parent audit

Modify above Post and Comment classes as below:

class Post
  include Mongoid::Document
  include Mongoid::Timestamps
  include Mongoid::History::Trackable

  field           :title
  field           :body
  field           :rating
  embeds_many     :comments

  track_history   :on => [:title, :body, :comments],
                  :modifier_field => :modifier,
                  :modifier_field_inverse_of => :nil,
                  :version_field => :version,
                  :track_create   =>  true,     # track create on Post
                  :track_update   =>  true,
                  :track_destroy  =>  false
end

class Comment
  include Mongoid::Document
  include Mongoid::Timestamps

  field             :title
  field             :body
  embedded_in       :post, :inverse_of => :comments
end

user = User.create(:name => "Aaron")
post = Post.create(:title => "Test", :body => "Post", :modifier => user)
comment = post.comments.build(:title => "test", :body => "comment", :modifier => user)
post.save
post.history_tracks.count # should be 1

comment.respond_to?(:history_tracks) # should be false

track = post.history_tracks.first
track.original # {}
track.modified # { "title" => "Test", "body" => "Post", "comments" => [{ "_id" => "575fa9e667d827e5ed00000d", "title" => "test", "body" => "comment" }], ... }

Whitelist the tracked attributes of embedded relations

If you don't want to track all the attributes of embedded relations in parent audit history, you can whitelist the attributes as below:

class Book
  include Mongoid::Document
  ...
  embeds_many :pages
  track_history :on => { :pages => [:title, :content] }
end

class Page
  include Mongoid::Document
  ...
  field :number
  field :title
  field :subtitle
  field :content
  embedded_in :book
end

It will now track only _id (Mandatory), title and content attributes for pages relation.

Track all blank changes

Normally changes where both the original and modified values respond with true to blank? (for example nil to false) aren't tracked. However, there may be cases where it's important to track such changes, for example when a field isn't present (so appears to be nil) then is set to false. To track such changes, set the track_blank_changes option to true (it defaults to false) when turning on history tracking:

class Book
  include Mongoid::Document
  ...
  field :summary
  track_history # Use default of false for track_blank_changes
end

# summary change not tracked if summary hasn't been set (or has been set to something that responds true to blank?)
Book.find(id).update_attributes(:summary => '')

class Chapter
  include Mongoid::Document
  ...
  field :title
  track_history :track_blank_changes => true
end

# title change tracked even if title hasn't been set
Chapter.find(id).update_attributes(:title => '')

Retrieving the list of tracked static and dynamic fields

class Book
  ...
  field             :title
  field             :author
  field             :price
  track_history     :on => [:title, :price]
end

Book.tracked_fields           #=> ["title", "price"]
Book.tracked_field?(:title)   #=> true
Book.tracked_field?(:author)  #=> false

Retrieving the list of tracked relations

class Book
  ...
  track_history :on => [:pages]
end

Book.tracked_relation?(:pages)    #=> true
Book.tracked_embeds_many          #=> ["pages"]
Book.tracked_embeds_many?(:pages) #=> true

Skip soft-deleted embedded objects with nested tracking

Default paranoia field is deleted_at. You can use custom field for each class as below:

class Book
  include Mongoid::Document
  include Mongoid::History::Trackable
  embeds_many :pages
  track_history on: :pages
end

class Page
  include Mongoid::Document
  include Mongoid::History::Trackable
  ...
  embedded_in :book
  history_settings paranoia_field: :removed_at
end

This will skip the page documents with removed_at set to a non-blank value from nested tracking

Formatting fields

You can opt to use a proc or string interpolation to alter attributes being stored on a history record.

class Post
  include Mongoid::Document
  include Mongoid::History::Trackable

  field           :title
  track_history   on: :title,
                  format: { title: ->(t){ t[0..3] } }

This also works for fields on an embedded relations.

class Book
  include Mongoid::Document
  include Mongoid::History::Trackable

  embeds_many :pages
  track_history on: :pages,
                format: { pages: { number: 'pg. %d' } }
end

class Page
  include Mongoid::Document
  include Mongoid::History::Trackable

  field :number, type: Integer
  embedded_in :book
end

Displaying history trackers as an audit trail

In your Controller:

# Fetch history trackers
@trackers = HistoryTracker.limit(25)

# get change set for the first tracker
@changes = @trackers.first.tracked_changes
  #=> {field: {to: val1, from: val2}}

# get edit set for the first tracker
@edits = @trackers.first.tracked_edits
  #=> { add: {field: val},
  #     remove: {field: val},
  #     modify: { to: val1, from: val2 },
  #     array: { add: [val2], remove: [val1] } }

In your View, you might do something like (example in HAML format):

%ul.changes
  - (@edits[:add]||[]).each do |k,v|
    %li.remove Added field #{k} value #{v}

  - (@edits[:modify]||[]).each do |k,v|
    %li.modify Changed field #{k} from #{v[:from]} to #{v[:to]}

  - (@edits[:array]||[]).each do |k,v|
    %li.modify
      - if v[:remove].nil?
        Changed field #{k} by adding #{v[:add]}
      - elsif v[:add].nil?
        Changed field #{k} by removing #{v[:remove]}
      - else
        Changed field #{k} by adding #{v[:add]} and removing #{v[:remove]}

  - (@edits[:remove]||[]).each do |k,v|
    %li.remove Removed field #{k} (was previously #{v})

Adding Userstamp on History Trackers

To track the User in the application who created the HistoryTracker, add the Mongoid::Userstamp gem to your HistoryTracker class. This will add a field called created_by and an accessor creator to the model (you can rename these via gem config).

class MyHistoryTracker
  include Mongoid::History::Tracker
  include Mongoid::Userstamp
end

Setting Modifier Class Name

If your app will track history changes to a user, Mongoid History looks for these modifiers in the User class by default. If you have named your 'user' accounts differently, you will need to add that to your Mongoid History config:

The following examples set the modifier class name using a Rails initializer:

If your app uses a class Author:

# config/initializers/mongoid-history.rb
# initializer for mongoid-history

Mongoid::History.modifier_class_name = 'Author'

Or perhaps you are namespacing to a module:

Mongoid::History.modifier_class_name = 'CMS::Author'

Conditional :if and :unless options

The track_history method supports :if and :unless options which will skip generating the history tracker unless they are satisfied. These options can take either a method Symbol or a Proc. They behave identical to how :if and :unless behave in Rails model callbacks.

  track_history on: [:ip],
                if: :should_i_track_history?,
                unless: ->(obj){ obj.method_to_skip_history }

Using an alternate changes method

Sometimes you may wish to provide an alternate method for determining which changes should be tracked. For example, if you are using embedded documents and nested attributes, you may wish to write your own changes method that includes changes from the embedded documents.

Mongoid::History provides an option named :changes_method which allows you to do this. It defaults to :changes, which is the standard changes method.

Note: Specify additional fields that are provided with a custom changes_method with the :on option.. To specify current fields and additional fields, use fields.keys + [:custom]

Example:

class Foo
  include Mongoid::Document
  include Mongoid::History::Trackable

  attr_accessor :ip

  track_history on: [:ip], changes_method: :my_changes

  def my_changes
    unless ip.nil?
      changes.merge(ip: [nil, ip])
    else
      changes
    end
  end
end

Example with embedded & nested attributes:

class Foo
  include Mongoid::Document
  include Mongoid::Timestamps
  include Mongoid::History::Trackable

  field      :bar
  embeds_one :baz
  accepts_nested_attributes_for :baz

  # use changes_with_baz to include baz's changes in this document's
  # history.
  track_history   on: fields.keys + [:baz], changes_method: :changes_with_baz

  def changes_with_baz
    if baz.changed?
      changes.merge(baz: summarized_changes(baz))
    else
      changes
    end
  end

  private
  # This method takes the changes from an embedded doc and formats them
  # in a summarized way, similar to how the embedded doc appears in the
  # parent document's attributes
  def summarized_changes obj
    obj.changes.keys.map do |field|
      next unless obj.respond_to?("#{field}_change")
      [ { field => obj.send("#{field}_change")[0] },
        { field => obj.send("#{field}_change")[1] } ]
    end.compact.transpose.map do |fields|
      fields.inject({}) {|map,f| map.merge(f)}
    end
  end
end

class Baz
  include Mongoid::Document
  include Mongoid::Timestamps

  embedded_in :foo
  field :value
end

For more examples, check out spec/integration/integration_spec.rb.

Multiple Trackers

You can have different trackers for different classes like so.

class First
  include Mongoid::Document
  include Mongoid::History::Trackable

  field :text, type: String
  track_history on: [:text],
                tracker_class_name: :first_history_tracker
end

class Second
  include Mongoid::Document
  include Mongoid::History::Trackable

  field :text, type: String
  track_history on: [:text],
                tracker_class_name: :second_history_tracker
end

class FirstHistoryTracker
  include Mongoid::History::Tracker
end

class SecondHistoryTracker
  include Mongoid::History::Tracker
end

Note that if you are using a tracker for an embedded object that is different from the parent's tracker, redos and undos will not work. You have to use the same tracker for these to work across embedded relationships.

If you are using multiple trackers and the tracker_class_name parameter is not specified, Mongoid::History will use the default tracker configured in the initializer file or whatever the first tracker was loaded.

Dependent Restrict Associations

When dependent: :restrict is used on an association, a call to destroy on the model will raise Mongoid::Errors::DeleteRestriction when the dependency is violated. Just be aware that this gem will create a history track document before the destroy call and then remove if an error is raised. This applies to all persistence calls: create, update and destroy.

See spec/integration/validation_failure_spec.rb for examples.

Thread Safety

Mongoid::History stores the tracking enable/disable flag in Thread.current. If the RequestStore gem is installed, Mongoid::History will automatically store variables in the RequestStore.store instead. RequestStore is recommended for threaded web servers like Thin or Puma.

Contributing

You're encouraged to contribute to Mongoid History. See CONTRIBUTING.md for details.

Copyright

Copyright (c) 2011-2024 Aaron Qian and Contributors.

MIT License. See LICENSE.txt for further details.