Mislav Marohnić edited this page Apr 19, 2014 · 7 revisions

Caching responses

Simple response body caching

FaradayMiddleware::Caching can be configured with a cache store that responds to read, write and fetch, such as one of ActiveSupport::Cache stores.

Example use:

cache_dir = File.join(ENV['TMPDIR'] || '/tmp', 'cache')

conn.response :caching, :ignore_params => %w[access_token] do cache_dir, :namespace => 'my_namespace',
    :expires_in => 3600  # one hour

In the above example, the return value of the block represents the cache store that the middleware will use. It's configured to cache each GET response for 1 hour.

Advanced HTTP caching

FaradayMiddleware::RackCompatible can be used to mount rack-cache to the middleware stack in order to perform caching per HTTP spec.

conn.use FaradayMiddleware::RackCompatible, Rack::Cache::Context,
  :metastore   => "file:#{cache_dir}/rack/meta",
  :entitystore => "file:#{cache_dir}/rack/body",
  :ignore_headers => %w[Set-Cookie X-Content-Digest]

In the above example, the stack is configured to cache successful responses to disk according to HTTP freshness/expiration information, and subsequent requests will be validated using information in Last-Modified/ETag headers.

The :ignore_headers option is important to enable caching even if the server where the data is coming from uses Rack::Cache, too. This is due to rack-cache issue #59.

Using RackCompatible middleware to mount Rack::Cache is kind of a hack. Consider using faraday-http-cache instead.