Rack::Cache

Rack::Cache is suitable as a quick drop-in component to enable HTTP caching for Rack-based applications that produce freshness (expires, cache-control) and/or validation (last-modified, etag) information:

  • Standards-based (RFC 2616)
  • Freshness/expiration based caching
  • Validation (if-modified-since / if-none-match)
  • vary support
  • cache-control public, private, max-age, s-maxage, must-revalidate, and proxy-revalidate.
  • Portable: 100% Ruby / works with any Rack-enabled framework
  • Disk, memcached, and heap memory storage backends

For more information about Rack::Cache features and usage, see:

https://rack.github.io/rack-cache/

Rack::Cache is not overly optimized for performance. The main goal of the project is to provide a portable, easy-to-configure, and standards-based caching solution for small to medium sized deployments. More sophisticated / high-performance caching systems (e.g., Varnish, Squid, httpd/mod-cache) may be more appropriate for large deployments with significant throughput requirements.

Installation

gem install rack-cache

Basic Usage

Rack::Cache is implemented as a piece of Rack middleware and can be used with any Rack-based application. If your application includes a rackup (.ru) file or uses Rack::Builder to construct the application pipeline, simply require and use as follows:

require 'rack/cache'

use Rack::Cache,
  metastore:    'file:/var/cache/rack/meta',
  entitystore:  'file:/var/cache/rack/body',
  verbose:      true

run app

Assuming you've designed your backend application to take advantage of HTTP's caching features, no further code or configuration is required for basic caching.

Using with Rails

# config/application.rb
config.action_dispatch.rack_cache = true
# or
config.action_dispatch.rack_cache = {
   verbose:     true,
   metastore:   'file:/var/cache/rack/meta',
   entitystore: 'file:/var/cache/rack/body'
}

You should now see Rack::Cache listed in the middleware pipeline:

rake middleware

more information

Using with Dalli

Dalli is a high performance memcached client for Ruby. More information at: https://github.com/mperham/dalli

require 'dalli'
require 'rack/cache'

use Rack::Cache,
  verbose:  true,
  metastore:    "memcached://localhost:11211/meta",
  entitystore:  "memcached://localhost:11211/body"

run app

Noop entity store

Does not persist response bodies (no disk/memory used).
Responses from the cache will have an empty body.
Clients must ignore these empty cached response (check for x-rack-cache response header).
Atm cannot handle streamed responses, patch needed.

require 'rack/cache'

use Rack::Cache,
 verbose: true,
 metastore: <any backend>
 entitystore: "noop:/"

run app

Ignoring tracking parameters in cache keys

It's fairly common to include tracking parameters which don't affect the content of the page. Since Rack::Cache uses the full URL as part of the cache key, this can cause unneeded churn in your cache. If you're using the default key class Rack::Cache::Key, you can configure a proc to ignore certain keys/values like so:

Rack::Cache::Key.query_string_ignore = proc { |k, v| k =~ /^(trk|utm)_/ }

License: MIT
Development