Rails Asset Caching Breaks First few page loads

Question

We're using Rails asset caching for JS and CSS like this:

<%= stylesheet_link_tag 'reset','global','admins','autocomplete', 'date_input', 'tablesorter', 'partners', 'jqmodal', :media => 'screen', :cache => set_asset_cache(:admins) %>
<%= javascript_include_tag :defaults, 'autocomplete', 'searchbox', 'jqmodal', :cache => set_asset_cache(:admins) %>

In our deploy we call rake tmp:assets:clear each time. The problem is that the first few page loads after a deploy come up with no css or js on the page. I guess until the cached all.js and all.css have been regenerated.

We deploy many times per day and this is scary for any users who happen to come across a busted page.

Have people found any way to make this smoother so the new cached assets are guaranteed to be there on the first new page load?

Answer 1

You could try warming the cache during deployment using wget, as an example (shamelessly reposted):

wget -r -nd --delete-after http://whatever.com/~popular/page/

However, this would have to be executed after you switch your symlink to your new deployment. A possibly more elegant solution might be to call the asset caching methods manually in your deploy, though I'm not sure how feasible that is. Here's where the caching is performed in Rails:

# File vendor/rails/actionpack/lib/action_view/helpers/asset_tag_helper.rb, line       273
273:       def javascript_include_tag(*sources)
274:         options = sources.extract_options!.stringify_keys
275:         concat  = options.delete("concat")
276:         cache   = concat || options.delete("cache")
277:         recursive = options.delete("recursive")
278: 
279:         if concat || (ActionController::Base.perform_caching && cache)
280:           joined_javascript_name = (cache == true ? "all" : cache) + ".js"
281:           joined_javascript_path = File.join(joined_javascript_name[/^#{File::SEPARATOR}/] ? ASSETS_DIR : JAVASCRIPTS_DIR, joined_javascript_name)
282: 
283:           unless ActionController::Base.perform_caching && File.exists?(joined_javascript_path)
284:             write_asset_file_contents(joined_javascript_path, compute_javascript_paths(sources, recursive))
285:           end
286:           javascript_src_tag(joined_javascript_name, options)
287:         else
288:           expand_javascript_sources(sources, recursive).collect { |source| javascript_src_tag(source, options) }.join("\n")
289:         end
290:       end

You might be able to modify the caching code and run it manually on deploy.