ActiveSnapshot
Simplified snapshots and restoration for ActiveRecord models and associations with a transparent white-box implementation.
Key Features:
- Create and Restore snapshots of a parent record and any specified child records
- Predictible and explicit behaviour provides much needed clarity to your restore logic
- Snapshots are created upon request only, we do not use any callbacks
- Tiny method footprint so its easy to completely override the logic later
Why This Library:
Model Versioning and Restoration require concious thought, design, and understanding. You should understand your versioning and restoration process completely. This gem's small API and fully understandable design fully supports this.
I do not recommend using paper_trail-association_tracking because it is mostly a blackbox solution which encourages you to set it up and then assume its Just WorkingTM. This makes for major data problems later. Dont fall into this trap. Instead read this gems brief source code completely before use OR copy the code straight into your codebase. Once you know it, then you are free.
Installation
gem 'active_snapshot'
Then generate and run the necessary migrations to setup the snapshots
and snapshot_items
tables.
rails generate active_snapshot:install
rake db:migrate
Then add include ActiveSnapshot
to your ApplicationRecord or individual models.
class ApplicationRecord < ActiveRecord::Base
include ActiveSnapshot
end
This defines the following associations on your models:
has_many :snapshots, as: :item, class_name: 'Snapshot'
has_many :snapshot_items, as: :item, class_name: 'SnapshotItem'
It defines an optional extension to your model: has_snapshot_children
.
It defines one instance method to your model: create_snapshot!
Using a different storage format
By default ActiveSnapshot encodes objects to JSON and stores in the database as plain text. If you prefer to have YAML encoded columns or native JSON DB columns you can configure this as follows:
ActiveSnapshot.config do |config|
config.storage_method = "serialized_json" # default, for text column
#config.storage_method = "serialized_yaml" # for text column
#config.storage_method = "native_json" # for json/jsonb column
end
If using a native json column, you should configure the storage_method
before generating the migration. If this step was missed then you would need to create a migration to change the :object
and :metadata
columns to json (or jsonb)
change_column :snapshots, :object, :json
change_column :snapshots, :metadata, :json
Basic Usage
You now have access to the following methods:
post = Post.first
# Create snapshot, all fields are optional
snapshot = post.create_snapshot!(
identifier: "snapshot_1",
user: current_user,
metadata: {
foo: :bar
},
)
# Restore snapshot and all its child snapshots
snapshot.restore!
# Destroy snapshot and all its child snapshots
# must be performed manually, snapshots and snapshot items are NEVER destroyed automatically
snapshot.destroy!
Tracking Associated / Child Records
class Post < ActiveRecord::Base
include ActiveSnapshot
has_snapshot_children do
### Executed in the context of the instance / self
### Reload record from database to ensure a clean state and eager load the specified associations
instance = self.class.includes(:tags, :ip_address, comments: [:comment_sub_records]).find(id)
### Define the associated records that will be restored
{
comments: instance.comments,
### Nested Associations can be handled by simply mapping them into an array
comment_sub_records: instance.comments.flat_map{|x| x.comment_sub_records },
tags: {
records: instance.
},
ip_address: {
record: instance.ip_address,
delete_method: ->(item){ item.release! }
}
}
end
end
Now when you run create_snapshot!
the associations will be tracked accordingly
Reifying Snapshot Items
You can view all of the reified snapshot items by calling the following method. Its completely up to you on how to use this data.
reified_parent, reified_children_hash = snapshot.fetch_reified_items
As a safety these records have the @readonly = true
attribute set on them. If you want to perform any write actions on the returned instances you will have to set @readonly = nil
.
reified_parent, reified_children_hash = snapshot.fetch_reified_items
reified_parent.instance_variable_set("@readonly", false)
Key Models Provided & Additional Customizations
A key aspect of this library is its simplicity and small API. For major functionality customizations we encourage you to first delete this gem and then copy this gems code directly into your repository.
I strongly encourage you to read the code for this library to understand how it works within your project so that you are capable of customizing the functionality later.
- SnapshotsConcern
- Defines
snapshots
andsnapshot_items
has_many associations - Defines
create_snapshot!
andhas_snapshot_children
methods
- Defines
- Snapshot
- Contains a unique
identifier
column (optional, but available for custom identification purposes) has_many :item_snapshots
- Contains a unique
- SnapshotItem
- Contains
object
column which contains an encoded database row belongs_to :snapshot
- Contains
Credits
Created & Maintained by Weston Ganger - @westonganger