Ruby on Rails

BemiHQ/bemi-rails

Bemi plugs into Ruby on Rails with Active Record and PostgreSQL to track database changes automatically. It unlocks robust context-aware audit trails and time travel querying inside your application.

This Ruby gem is a recommended Ruby on Rails integration, enabling you to pass application-specific context when performing database changes. This can include context such as the 'where' (API endpoint, worker, etc.), 'who' (user, cron job, etc.), and 'how' behind a change, thereby enriching the information captured by Bemi.

See this example repo as a Ruby on Rails Todo app that automatically tracks and contextualizes all changes.

Prerequisites

• PostgreSQL 14+
• Ruby on Rails

Installation

1. Install the gem

Gemfile

gem 'bemi-rails'

2. Generate a Rails migration file to add lightweight PostgreSQL triggers for passing application context with all data changes into PostgreSQL replication log

bin/rails g bemi:migration

3. Run the rails migration

bin/rails db:migrate

Usage

Now you can easily specify custom application context that will be automatically passed with all data changes.

app/controllers/application_controller.rb

class ApplicationController < ActionController::Base
  before_action :set_bemi_context

  private

  def set_bemi_context
    Bemi.set_context(
      user_id: current_user&.id,
      endpoint: "#{request.method} #{request.path}",
      method: "#{self.class}##{action_name}",
    )
  end
end

Application context:

• Is bound to the current Ruby thread. So it is isolated to a single HTTP request or background job.
• Is used only with INSERT, UPDATE, DELETE SQL queries performed via Active Record. Otherwise, it is a no-op.
• Is passed directly into PG Write-Ahead Log with data changes without affecting the structure of the database and SQL queries.

Application context will automatically include the original SQL query that performed data changes, which is generally useful for troubleshooting purposes.

Database connection

Connect your PostgreSQL source database on bemi.io to start ingesting and storing all data changes stitched together with application-specific context. The database connection details can be securely configured through the dashboard UI in a few seconds.

Once your destination PostgreSQL database has been fully provisioned, you'll see a "Connected" status. You can now test the connection after making database changes in your connected source database:

psql postgres://[USERNAME]:[PASSWORD]@[HOSTNAME]:5432/[DATABASE] -c 'SELECT "primary_key", "table", "operation", "before", "after", "context", "committed_at" FROM changes;'

 primary_key | table  | operation |                       before                    |                       after                      |                                context                                                   |      committed_at
-------------+--------+-----------+-------------------------------------------------+--------------------------------------------------+------------------------------------------------------------------------------------------+------------------------
 26          | todos  | CREATE    | {}                                              | {"id": 26, "task": "Sleep", "completed": false}  | {"user_id": 187234, "endpoint": "POST /todos", "method": "TodosController#create"}       | 2023-12-11 17:09:09+00
 27          | todos  | CREATE    | {}                                              | {"id": 27, "task": "Eat", "completed": false}    | {"user_id": 187234, "endpoint": "POST /todos", "method": "TodosController#create"}       | 2023-12-11 17:09:11+00
 28          | todos  | CREATE    | {}                                              | {"id": 28, "task": "Repeat", "completed": false} | {"user_id": 187234, "endpoint": "POST /todos", "method": "TodosController#create"}       | 2023-12-11 17:09:13+00
 26          | todos  | UPDATE    | {"id": 26, "task": "Sleep", "completed": false} | {"id": 26, "task": "Sleep", "completed": true}   | {"user_id": 187234, "endpoint": "POST /todos/26", "method": "TodosController#update"}    | 2023-12-11 17:09:15+00
 27          | todos  | DELETE    | {"id": 27, "task": "Eat", "completed": false}   | {}                                               | {"user_id": 187234, "endpoint": "DELETE /todos/27", "method": "TodosController#destroy"} | 2023-12-11 17:09:18+00

See Destination Database for more details.

Data change querying

Lastly, connect to the Bemi PostgreSQL destination database to easily query change data from your application.

To query historical data, configure an additional database connection with Active Record:

config/database.yml

production:
  primary:
    <<: *default
    # Your regular database settings go here
  bemi:
    adapter: postgresql
    encoding: unicode
    pool: <%= ENV["RAILS_MAX_THREADS"] || 5 %>
    host: <%= ENV["DESTINATION_DB_HOST"] %>
    port: <%= ENV["DESTINATION_DB_PORT"] %>
    database: <%= ENV["DESTINATION_DB_DATABASE"] %>
    username: <%= ENV["DESTINATION_DB_USERNAME"] %>
    password: <%= ENV["DESTINATION_DB_PASSWORD"] %>
    migrations_paths: db/bemi_migrate

Create a new model that connects to the destination database:

app/models/bemi_record.rb

# frozen_string_literal: true

class BemiRecord < ApplicationRecord
  self.abstract_class = true
  connects_to database: { writing: :bemi, reading: :bemi }
end

Create a new BemiChange model to access all data changes:

app/models/bemi_change.rb

# frozen_string_literal: true

class BemiChange < BemiRecord
  include Bemi::ChangeQueryHelpers
  self.table_name = 'changes'
end

Add a helper module to the tracked models or your main ApplicationRecord and set bemi_change_class:

app/models/application_record.rb

class ApplicationRecord < ActiveRecord::Base
  include Bemi::RecordQueryHelpers
  bemi_change_class 'BemiChange'
  # ...
end

Query changes

BemiChange.take
# => #<BemiChange:0x000000012f7fab40
#  id: "fe85c5e2-489c-4172-83dd-b58f25edb412",
#  committed_at: Tue, 25 Apr 2024 22:15:50.890000000 UTC +00:00,
#  table: "todos",
#  primary_key: "27",
#  operation: "UPDATE",
#  before: {"id"=>27, "task"=>"Walk", "is_completed"=>false}>
#  after: {"id"=>27, "task"=>"Run", "is_completed"=>true},
#  context:
#   {"SQL"=> "UPDATE \"public\".\"todos\" SET \"task\" = $1, \"is_completed\" = $2 WHERE \"public\".\"todos\".\"id\" = $3",
#    "user_id"=>1,
#    "api_endpoint"=>"/todos/complete"},
#  ...

Diff changed values

BemiChange.take.diff
# => { "task" => ["Walk", "Run"], "completed" => [false, true] }

Query change by record

record = Todo.find(...)
record.bemi_changes.limit(10)

Filter by values

# Query by the previous values
record.bemi_changes.before(task: 'Walk')
record.bemi_changes.before(task: 'Walk', completed: false)
record.bemi_changes.before_not(task: 'Run')

# Query by the new values
record.bemi_changes.after(task: 'Run')
record.bemi_changes.after(task: 'Run', completed: true)
record.bemi_changes.after_not(task: 'Walk')

# Query by the context values
record.bemi_changes.context(user_id: 1)
record.bemi_changes.context(user_id: 1, api_endpoint: '/tasks/complete')
record.bemi_changes.context_not(user_id: 123)

# Chain methods
record.bemi_changes.before(task: 'Walk').after(task: 'Run')

Filter by operation

record.bemi_changes.created
record.bemi_changes.updated
record.bemi_changes.deleted

Sort changes

record.bemi_changes.asc
record.bemi_changes.desc

Build a custom query

changes = BemiChange.
  where(table: 'todos', operation: 'UPDATE').
  where('context @> ?', { user_id: 1 }.to_json).
  order(committed_at: :desc).
  limit(10)

Alternative gems

	Bemi	PaperTrail	Audited	Logidze
Open source	✅	✅	✅	✅
Capturing record deletions	✅	✅	✅	❌
Reliability and accuracy	✅	❌	❌	❌
Scalability	✅	❌	❌	❌
No performance impact	✅	❌	❌	❌
Easy-to-use UI	✅	❌	❌	❌

License

Distributed under the terms of the LGPL-3.0. If you need to modify and distribute the code, please release it to contribute back to the open-source community.