Class: Rack::PageCache

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/page_cache.rb

Overview

PageCache is a Rack middleware that caches responses for successful GET requests to disk. This works similar to Rails’ page caching, allowing you to cache dynamic pages to static files that can be served directly by a front end webserver.

Instance Method Summary collapse

Constructor Details

#initialize(app, cache, &block) ⇒ PageCache

Initialize a new ReponseCache object with the given arguments. Arguments:

  • app : The next middleware in the chain. This is always called.

  • cache : all cached files will use this directory as the root directory.



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# File 'lib/rack/page_cache.rb', line 12

def initialize(app, cache, &block)
  @app = app
  @cache = cache.sub(/\/*$/, "/") # normalize path to have a single trailing slash.
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/rack/page_cache.rb', line 17

def call(env)
  res = @app.call(env)
  page_cache(env, res)
  res
end

#matching_content_type?(env, res) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rack/page_cache.rb', line 55

def matching_content_type?(env, res)
  return unless content_type = res[1]['Content-Type']
  
  path_info = env['PATH_INFO']
  mime_types = MIME::Types.type_for(path_info)
  mime_types = [ "text/html" ] if mime_types.empty?

  mime_types.any? do |mime_type|
    content_type.index(mime_type)
  end
end

#page_cache(env, res) ⇒ Object 



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# File 'lib/rack/page_cache.rb', line 23

def page_cache(env, res)
  # If the request was successful (response status 200), was a GET request, and
  # had an empty query string, this request is probably cacheable.
  return res unless env['REQUEST_METHOD'] == 'GET' and res[0] == 200 and env['QUERY_STRING'] == ""
  
  # But the content_type, that can be derived from the request path - and is what
  # the web server would use in the next request - must match the content type
  # in the response.
  return unless matching_content_type?(env, res)

  # Build path for cache file. The path must not contain '..', to prevent directory
  # traversal attacks.
  path = env['PATH_INFO']
  return if path.include?('..')
  
  # We cannot use File.join here, because this would eat the double slashes in the path_info.
  # The @cache instance variable, however, is normalized to end in a single slash.
  path = "#{@cache}/#{path}" 
  
  # If the cache file exists already, then we run inside rackup. 
  # The cached file will be delivered by Rack::Static, and we don't need
  # (and don't want to: this zeroes the file, for some reason) to rewrite the path
  return if File.exists?(path)
  
  FileUtils.mkdir_p(File.dirname(path))
  File.open(path, 'wb') do |f| 
    res[2].each do |c| 
      f.write(c)
    end
  end
end