Emailing with Delayed Job

We used Delayed Job to queue emails sent out to users, both to offload that blocking process and for scheduling. It has worked well so far, but recently there were some strange bugs popping up. Some emails were stuck in the queue, and the error message was about bad YAML syntax.

Delayed Job serialized objects in its handler field, and, with some user input that's not encoded properly, created incorrect YAML. For example, this could happen:

id: 1
  foo: 'here is some 'text'
  bar: 'something else'

Notice the odd number of single quotes in foo? Yeah, that's bad. Since we already had that kind of data saved, we needed another way to fix this.

Instead of having methods in the notifier.rb file like so:

def forgot_password(user)
  ...
end

We did it like this:

def forgot_password(user_id)
  user = User.find(user_id)
  ...
end

Delayed Job serialized just the user id and not the entire user object, so any potentially harmful data wasn't saved. This was more expensive since the objects had to get instantiated again, but sending out email wasn't expensive for our app, so this solution worked well.

If you ever get strange YAML syntax errors from delayed job, perhaps this method will work for you.