Parent

Rack::Cache::MetaStore

The MetaStore is responsible for storing meta information about a request/response pair keyed by the request’s URL.

The meta store keeps a list of request/response pairs for each canonical request URL. A request/response pair is a two element Array of the form:

[request, response]

The request element is a Hash of Rack environment keys. Only protocol keys (i.e., those that start with “HTTP_”) are stored. The response element is a Hash of cached HTTP response headers for the paired request.

The MetaStore class is abstract and should not be instanstiated directly. Concrete subclasses should implement the protected read, write, and purge methods. Care has been taken to keep these low-level methods dumb and straight-forward to implement.

Public Instance Methods

cache_key(request) click to toggle source

Generate a cache key for the request.

# File lib/rack/cache/metastore.rb, line 88
def cache_key(request)
  keygen = request.env['rack-cache.cache_key'] || Key
  keygen.call(request)
end
invalidate(request, entity_store) click to toggle source

Invalidate all cache entries that match the request.

# File lib/rack/cache/metastore.rb, line 94
def invalidate(request, entity_store)
  modified = false
  key = cache_key(request)
  entries =
    read(key).map do |req, res|
      response = restore_response(res)
      if response.fresh?
        response.expire!
        modified = true
        [req, persist_response(response)]
      else
        [req, res]
      end
    end
  write key, entries if modified
end
lookup(request, entity_store) click to toggle source

Locate a cached response for the request provided. Returns a Rack::Cache::Response object if the cache hits or nil if no cache entry was found.

# File lib/rack/cache/metastore.rb, line 28
def lookup(request, entity_store)
  key = cache_key(request)
  entries = read(key)

  # bail out if we have nothing cached
  return nil if entries.empty?

  # find a cached entry that matches the request.
  env = request.env
  match = entries.detect{|req,res| requests_match?(res['Vary'], env, req)}
  return nil if match.nil?

  _, res = match
  if body = entity_store.open(res['X-Content-Digest'])
    restore_response(res, body)
  else
    # TODO the metastore referenced an entity that doesn't exist in
    # the entitystore. we definitely want to return nil but we should
    # also purge the entry from the meta-store when this is detected.
  end
end
store(request, response, entity_store) click to toggle source

Write a cache entry to the store under the given key. Existing entries are read and any that match the response are removed. This method calls write with the new list of cache entries.

# File lib/rack/cache/metastore.rb, line 53
def store(request, response, entity_store)
  key = cache_key(request)
  stored_env = persist_request(request)

  # write the response body to the entity store if this is the
  # original response.
  if response.headers['X-Content-Digest'].nil?
    if request.env['rack-cache.use_native_ttl'] && response.fresh?
      digest, size = entity_store.write(response.body, response.ttl)
    else
      digest, size = entity_store.write(response.body)
    end
    response.headers['X-Content-Digest'] = digest
    response.headers['Content-Length'] = size.to_s unless response.headers['Transfer-Encoding']
    response.body = entity_store.open(digest)
  end

  # read existing cache entries, remove non-varying, and add this one to
  # the list
  vary = response.vary
  entries =
    read(key).reject do |env,res|
      (vary == res['Vary']) &&
        requests_match?(vary, env, stored_env)
    end

  headers = persist_response(response)
  headers.delete 'Age'

  entries.unshift [stored_env, headers]
  write key, entries
  key
end

Protected Instance Methods

purge(key) click to toggle source

Remove all cached entries at the key specified. No error is raised when the key does not exist.

# File lib/rack/cache/metastore.rb, line 163
def purge(key)
  raise NotImplemented
end
read(key) click to toggle source

Locate all cached request/response pairs that match the specified URL key. The result must be an Array of all cached request/response pairs. An empty Array must be returned if nothing is cached for the specified key.

# File lib/rack/cache/metastore.rb, line 150
def read(key)
  raise NotImplemented
end
write(key, negotiations) click to toggle source

Store an Array of request/response pairs for the given key. Concrete implementations should not attempt to filter or concatenate the list in any way.

# File lib/rack/cache/metastore.rb, line 157
def write(key, negotiations)
  raise NotImplemented
end

[Validate]

Generated with the Darkfish Rdoc Generator 2.