Class: Redmine::HttpCaching

Inherits:
SimpleDelegator
  • Object
show all
Defined in:
lib/redmine/http_caching.rb

Overview

A decorator object for RestClient that adds caching capabilities to regular RestClient objects. It wraps normal request methods and uses the Etag and If-None-Match headers to locally store responses. On subsequent requests for the same resource, we can skip downloading the entire body when the server indicates nothing has changed (Not Modified).

A cache is used to keep track of responses. This is assumed to support the Pstore interface, responding to #transaction, #[] and #[]= methods.

Usage example:

require 'pstore'
cache = PStore.new('cache.pstore')
rest_client = RestClient.new
caching_rest_client = HttpCaching.new(rest_client, cache)
caching_rest_client.get('/path')

Instance Method Summary collapse

Constructor Details

#initialize(http, cache) ⇒ HttpCaching 



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# File 'lib/redmine/http_caching.rb', line 21

def initialize(http, cache)
  @cache = cache
  super(http)
end

Instance Method Details

#get(path, headers = {}) ⇒ Object

Wrap RestClient#get to provide HTTP caching.

New requests are stored in a cache if they have an Etag header. On subsequent requests to the same resource, a If-None-Match header is sent along, using the original Etag value. The server can then indicate that nothing has changed, which will trigger this decorator to return the cached response – rather than downloading a whole new copy of the same data.



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# File 'lib/redmine/http_caching.rb', line 34

def get(path, headers = {})
  cached_response = fetch_cached_response(path)
  if cached_response
    headers = headers.merge 'If-None-Match' => cached_response['Etag']
  end
  response = super(path, headers)
  case response
  when Net::HTTPNotModified then cached_response
  else
    cache_response(path, response)
    response
  end
end