How to invoke a method every time database is modified

Question

I am writing a Ruby on Rails app and I want a method to be called every time the database is modified. Is it possible to do this without inserting a method call in every location where the database is modified?

Answer 1

Depends on the database. Many databases have very powerful stored procedure languages that can, among other things, invoke web services.

You could have a trigger on the important database tables call a ruby web service that calls your method.

Or you can have triggers that update an event table, and then have a process that watches for changes on that table and then fires the method.

There's likely some meta-programming magic that you might be able to use to tweak your ruby code to invoke the change as well.

All sorts of options.

Answer 2

Have you considered using: after_update or before_update in ActiveRecord:

http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html

Answer 3

If you want to log all models:

Monkey patch the ActiveRecord::Base class.

class ActiveRecord::Base
  after_save :log_something
  after_destroy :log_something

private
  def log_something

  end
end

For a specific model:

class User < ActiveRecord::Base
  after_save :log_something
  after_destroy :log_something

private
  def log_something

  end
end

Answer 4

I like KandadaBooggu's answer but if you did not want to monkey with AR you might be able to do this with an Observer.

class AllObserver < ActiveRecord::Observer
  observe :model_a, :model_b

  def after_save(record)
    logger.info("CREATED #{record.class}")
  end

  def after_update(record)
    logger.info("UPDATED #{record.class}")
  end
end

Just add the models that you want to observer. In this example it will log updates to ModelA and ModelB