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:


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.


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

Either of these but not both:

# config/application.rb
config.action_dispatch.rack_cache = true
# or
config.middleware.use 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

License: MIT
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