pg advisory locks

pg_advisory_lock.rb

class LockManager
  def self.with_transaction_lock(lock_name)
    lock_id = Zlib.crc32(lock_name.to_s)
    ActiveRecord::Base.transaction do
      ActiveRecord::Base.connection.execute("SELECT pg_advisory_xact_lock(#{lock_id})")
      yield
    end
  end

  def self.with_session_lock(lock_name)
    lock_id = Zlib.crc32(lock_name.to_s)
    begin
      ActiveRecord::Base.connection.execute("SELECT pg_advisory_lock(#{lock_id})")
      yield
    ensure
      ActiveRecord::Base.connection.execute("SELECT pg_advisory_unlock(#{lock_id})")
    end
  end
end


LockManager.with_transaction_lock("subscription_usage_#{user_id}") do
  user = User.find(user_id)
  new_usage = user.current_subscription_usage
  user.update_attributes!(subscription_usage: new_usage)
end