Question

I’m developing a Rails application that has a background process that updates some user information. In order to do so, this method has to delete all the existing information (stored in another table) and get new information from the Internet. The problem is that if something goes wrong in the midtime users don’t have information until the process runs again.

there is something to do like:

transaction = EntityUser.delete_all(:user_id => @current_user.id)
#instructions that adds new  entity
...
...
transaction.commit

can anyone suggest something that i can do to avoid this kind of problem?

thank you

Answer 1

Read about ActiveRecord::Transactions. You can wrap everything in a block

ActiveRecord::Base.transaction do
  EntityUser.delete_all(:user_id => @current_user.id)

  # ...
end

If something goes wrong, you can call raise ActiveRecord::Rollback within that block to cause all changes to the database within the transaction block to be reverted.

---

Another thought is to soft-delete the EntityUser instance(s) for a User instead of actually removing them from the database. There are gems to help you with this functionality such as acts_as_paranoid.

You would

1. soft-delete the EntityUser instance(s)
2. Fetch and build the new EntityUser instance(s)
3. (Optionally) flush the soft-deleted instance(s) from the database if everything went well

If something goes wrong using this method it’s easy to just un-delete the soft-deleted records.