- Clone the repository
- Change directory to xbe
cd xbe - Install dependencies
bundle install - You need a postgres server running with username as 'root' and password as 'root' and database xbe with root getting all privileges
- Create database
rake db:create - Install db changes
rake db:migrate - In new terminal run to start sidekiq
bundle exec sidekiq -e development -C config/sidekiq.yml - In new terminal run
rake database_listener
- gem 'hairtrigger', '~> 1.0' // For creating triggers within rails env
- gem 'sidekiq', '~> 7.1', '>= 7.1.2' # For background processes
- gem "rspec-rails" # For testing.
- Invoices - id (uuid), invoice_no(string), total_amount(int), timestamps
- Invoice_items - id(uuid), invoice_id(foreign_key), quantity(int), amount_per_unit(int), total_amount(int), timestamps
- Triggers on create, update, delete
- Every trigger contains pg_notify which sends messages on 'trigger_changes' channel
- Notifications - event(string), payload(json)
- database_listener - This queues DatabaseNotifications background job which in turn listens to pg_notify()
- Have used postgres triggers as we need the application to get notified even if changes are directly done on database
- Installed hair-trigger gem which lets me create triggers in model files itself
- 3 tables - invoice, invoice_items(references invoice table via foreign key), notifications
- In invoice_item.rb file I have created triggers when quantity, amount_per_unit changes for invoice_item. It changes total_amount in invoice_table.
- The invoice_items trigger also use pg_notify() for inter-process communication and sends message to rails application
- Created an ApplicationJob which uses Sidekiq and listens to pg_notify commands. It also writes to Notifications table whenever a prompt is received.
- Created rake task "database_listener" which queues the above job
- Have written just 1 rspec test but have could not proceed for paucity of time.