tree_path attribute can grow enormously

[hwo411]

Hi everyone.

Recently on our project, we ran into a fairly rare bug, which leads to livelock. Our sidekiq jobs for one of the users started calling each other without doing anything useful. This caused a lot of problems in the place we didn't expect - logs. It had generated more than 60GB of logs by the time we discovered the issue. request_depth was more than 167k.

While fixing the causes of such behavior is unquestionably important, I think such vulnerability should also be fixed in the gem. My thoughts on it - one will never need more than 30-50 first and last items of tree_path. It's important how things had begun and how they ended. In the middle, it'll most likely be a loop, and it can always be investigated through the other log entries with the same request_id and some lower request_depth.

So I'd suggest to separate tree_path to tree_root and tree_node parameters and introduce a config value for setting max length for each of the fields.