Faraday Http Cache
a Faraday middleware that respects HTTP cache, by checking expiration and validation of the stored responses.
Add it to your Gemfile:
Usage and configuration
You have to use the middleware in the Faraday instance that you want to,
along with a suitable
store to cache the responses. You can use the new
shortcut using a symbol or passing the middleware class
client = Faraday.new do |builder| builder.use :http_cache, store: Rails.cache # or builder.use Faraday::HttpCache, store: Rails.cache builder.adapter Faraday.default_adapter end
The middleware accepts a
store option for the cache backend responsible for recording
the API responses that should be stored. Stores should respond to
just like an object from the
# Connect the middleware to a Memcache instance. store = ActiveSupport::Cache.lookup_store(:mem_cache_store, ['localhost:11211']) client = Faraday.new do |builder| builder.use :http_cache, store: store builder.adapter Faraday.default_adapter end # Or use the Rails.cache instance inside your Rails app. client = Faraday.new do |builder| builder.use :http_cache, store: Rails.cache builder.adapter Faraday.default_adapter end
The default store provided is a simple in memory cache that lives on the client instance. This type of store might not be persisted across multiple processes or connection instances so it is probably not suitable for most production environments. Make sure that you configure a store that is suitable for you.
JSON module is used for serialization by default, which can struggle with unicode
characters in responses. For example, if your JSON returns
"name": "Raül" then you might see
Response could not be serialized: "\xC3" from ASCII-8BIT to UTF-8. Try using Marshal to serialize.
For full unicode support, or if you expect to be dealing with images, you can use
Marshal instead. Alternatively you could use another json library like
client = Faraday.new do |builder| builder.use :http_cache, store: Rails.cache, serializer: Marshal builder.adapter Faraday.default_adapter end
You can provide a
:logger option that will be receive debug informations based on the middleware
client = Faraday.new do |builder| builder.use :http_cache, store: Rails.cache, logger: Rails.logger builder.adapter Faraday.default_adapter end client.get('http://site/api/users') # logs "HTTP Cache: [GET users] miss, store"
In addition to logging you can instrument the middleware by passing in an
such as ActiveSupport::Notifications (compatible objects are also allowed).
http_cache.faraday will be published every time the middleware
processes a request. In the event payload,
:env contains the response Faraday env and
:cache_status contains a Symbol indicating the status of the cache processing for that request:
:unacceptablemeans that the request did not go through the cache at all.
:missmeans that no cached response could be found.
:invalidmeans that the cached response could not be validated against the server.
:validmeans that the cached response could be validated against the server.
:freshmeans that the cached response was still fresh and could be returned without even calling the server.
client = Faraday.new do |builder| builder.use :http_cache, store: Rails.cache, instrumenter: ActiveSupport::Notifications builder.adapter Faraday.default_adapter end # Subscribes to all events from Faraday::HttpCache. ActiveSupport::Notifications.subscribe "http_cache.faraday" do |*args| event = ActiveSupport::Notifications::Event.new(*args) cache_status = event.payload[:cache_status] statsd = Statsd.new case cache_status when :fresh, :valid statsd.increment('api-calls.cache_hits') when :invalid, :miss statsd.increment('api-calls.cache_misses') when :unacceptable statsd.increment('api-calls.cache_bypass') end end
See it live
You can clone this repository, install its dependencies with Bundler (run
bundle install) and
execute the files under the
examples directory to see a sample of the middleware usage.
What gets cached?
The middleware will use the following headers to make caching decisions:
s-maxage directives are checked.
Shared vs. non-shared caches
By default, the middleware acts as a "shared cache" per RFC 2616. This means it does not cache
Cache-Control: private. This behavior can be changed by passing in the
:shared_cache configuration option:
client = Faraday.new do |builder| builder.use :http_cache, shared_cache: false builder.adapter Faraday.default_adapter end client.get('http://site/api/some-private-resource') # => will be cached
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