Capistrano3 Fast Assets

A Capistrano 3 plugin to deploy Ruby on Rails apps faster.

The standard way to deploy Rails apps which make use of the Asset Pipeline is to have Capistrano call rake assets:precompile as part of the deploy. This has three problems.

1. The precompile task can get very slow.
2. Very few deploys will actually change any assets
3. Not all servers need a copy of assets (e.g. workers that don't server http requests; sometimes not all app-servers, depending on routing), but all apps probably will need a copy of the manifest.yml that is generated by assets:precompile.

The fast-assets plugin speeds up deploys in two ways.

1. Assets are only compiled if a change to asset-ish locations has been made
2. Assets are only compiled on nominated servers and the manifest.yml file is then copied to other servers.

Usage

Require capistrano3-fast-assets in your Gemfile Require capistrano/fast-assets in your Capfile.

Attachs to deploy:after. Any change between the currently deployed revision and the next deployed revision should trigger a full recompile of assets. If it doesn't, or you want to force the issue set FORCE_COMPILE=1 as part of the deploy.

Default Settings

set :asset_manifest_path, "config/manifest.yml"
set :asset_locations, ["app/assets", "lib/assets", "vendor/assets", "Gemfile.lock"]
set :asset_compiler_role, :asset_compiler
set :rails_env, fetch(:rails_env) || fetch(:stage)

Gotchas

• Not compatible with Capistrano 2.
• Probably not compatible with the official capistrano-rails gem
• Only compatible with git as SCM.
• We don't use the default public/assets/manifest.yml location. We store the manifest in config/ so that each deploy retains a copy and never overwrites a shared manifest.yml.
• We symlink shared/public/assets to current/public/assets. This means that all previous assets remain available for future deploys. This is considered a feature, not a bug. Anyone looking at a cached page or old HTML email should still be able to fetch the original assets from that revision.
• This was build very much as an in-house tool, YMMV.