Just to vent my frustrations a little bit I thought I would post a heisenbug that hit me today. Today, I realised that some pages on my production site were throwing javascript errors (jQuery Mobile / Rails 3.1). The same site on my development machine was working fine. Of course being a production site, debugging the javascript to understand what was different proved difficult. Looking at the docs on the asset pipeline (http://guides.rubyonrails.org/asset_pipeline.html) I noted a nifty little feature which is the ability to add ?debug_assets=true to the end of a url to enable debugging of the asset pipeline.

Lo and behold, as soon as I turn this on, the javascript errors disappear and the site works properly again. I am sure this is indicative of some deeper underlying problem with what I have set up – but I haven’t been able to trace it down yet.