Improve Rails Asset Caching with MD5 and virtual folders

• MD5 only changes on content-change and is identical on all servers
• Virtual folders are CDN/proxy/... cacheable and transparent via nginx/apache rewrite rule

Results

/foo/bar.jpg ... will be ...

# default + simple rewrite rules
/asset-v1afd23/foo/bar.jpg  # style: folder   method: MD5

# rails 3.1-ish, but complicated rewrite rules
/foo/bar-asset-v1afd23.jpg  # style: suffix   method: MD5

# no rewrite rule needed (great for development)
/foo/bar.jpg?1afd23         # style: query    method: MD5

# different methods ...
/asset-v1308942465/foo/bar.jpg  # style: folder   method: mtime
/asset-vxxx/foo/bar.jpg         # style: folder   method: ENV['RAILS_ASSET_ID'] = 'xxx'

# configure
VirtualAssetPath.style = :folder # default
VirtualAssetPath.style = :MD5    # default

Install

(only tested on rails 2 atm)

./script/plugin install git://github.com/grosser/virtual_asset_path.git

Or gem install virtual_asset_path

Nginx config

rewrite  ^/asset-v[a-z0-9]+(.*) $1; # style: folder
??? # style: suffix

Apache config

??? # style: folder
??? # style: suffix

Tips

• [Speed] MD5 takes ~0.1 ms/file (results are cached per instance if cache_asset_timestamps is active)
• [Speed] mtime takes ~0.005 ms/file (...)

TODO

• Rails 3.1 support -- things got much more complicated ...

Author

Michael Grosser
michael@grosser.it
Hereby placed under public domain, do what you want, just do not hold me accountable...