/usr/lib/ruby/vendor_ruby/rack/cache/metastore.rb is in ruby-rack-cache 1.2-4.
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require 'digest/sha1'
require 'rack/utils'
require 'rack/cache/key'
module Rack::Cache
# 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.
class MetaStore
# 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.
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
# 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.
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
# Generate a cache key for the request.
def cache_key(request)
keygen = request.env['rack-cache.cache_key'] || Key
keygen.call(request)
end
# Invalidate all cache entries that match the request.
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
private
# Extract the environment Hash from +request+ while making any
# necessary modifications in preparation for persistence. The Hash
# returned must be marshalable.
def persist_request(request)
env = request.env.dup
env.reject! { |key,val| key =~ /[^0-9A-Z_]/ || !val.respond_to?(:to_str) }
env
end
# Converts a stored response hash into a Response object. The caller
# is responsible for loading and passing the body if needed.
def restore_response(hash, body=nil)
status = hash.delete('X-Status').to_i
Rack::Cache::Response.new(status, hash, body)
end
def persist_response(response)
hash = response.headers.to_hash
hash['X-Status'] = response.status.to_s
hash
end
# Determine whether the two environment hashes are non-varying based on
# the vary response header value provided.
def requests_match?(vary, env1, env2)
return true if vary.nil? || vary == ''
vary.split(/[\s,]+/).all? do |header|
key = "HTTP_#{header.upcase.tr('-', '_')}"
env1[key] == env2[key]
end
end
protected
# 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.
def read(key)
raise NotImplemented
end
# 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.
def write(key, negotiations)
raise NotImplemented
end
# Remove all cached entries at the key specified. No error is raised
# when the key does not exist.
def purge(key)
raise NotImplemented
end
private
# Generate a SHA1 hex digest for the specified string. This is a
# simple utility method for meta store implementations.
def hexdigest(data)
Digest::SHA1.hexdigest(data)
end
public
# Concrete MetaStore implementation that uses a simple Hash to store
# request/response pairs on the heap.
class Heap < MetaStore
def initialize(hash={})
@hash = hash
end
def read(key)
if data = @hash[key]
Marshal.load(data)
else
[]
end
end
def write(key, entries)
@hash[key] = Marshal.dump(entries)
end
def purge(key)
@hash.delete(key)
nil
end
def to_hash
@hash
end
def self.resolve(uri)
new
end
end
HEAP = Heap
MEM = HEAP
# Concrete MetaStore implementation that stores request/response
# pairs on disk.
class Disk < MetaStore
attr_reader :root
def initialize(root="/tmp/rack-cache/meta-#{ARGV[0]}")
@root = File.expand_path(root)
FileUtils.mkdir_p(root, :mode => 0755)
end
def read(key)
path = key_path(key)
File.open(path, 'rb') { |io| Marshal.load(io) }
rescue Errno::ENOENT, IOError
[]
end
def write(key, entries)
tries = 0
begin
path = key_path(key)
File.open(path, 'wb') { |io| Marshal.dump(entries, io, -1) }
rescue Errno::ENOENT, IOError
Dir.mkdir(File.dirname(path), 0755)
retry if (tries += 1) == 1
end
end
def purge(key)
path = key_path(key)
File.unlink(path)
nil
rescue Errno::ENOENT, IOError
nil
end
private
def key_path(key)
File.join(root, spread(hexdigest(key)))
end
def spread(sha, n=2)
sha = sha.dup
sha[n,0] = '/'
sha
end
public
def self.resolve(uri)
path = File.expand_path(uri.opaque || uri.path)
new path
end
end
DISK = Disk
FILE = Disk
# Stores request/response pairs in memcached. Keys are not stored
# directly since memcached has a 250-byte limit on key names. Instead,
# the SHA1 hexdigest of the key is used.
class MemCacheBase < MetaStore
extend Rack::Utils
# The MemCache object used to communicated with the memcached
# daemon.
attr_reader :cache
# Create MemCache store for the given URI. The URI must specify
# a host and may specify a port, namespace, and options:
#
# memcached://example.com:11211/namespace?opt1=val1&opt2=val2
#
# Query parameter names and values are documented with the memcached
# library: http://tinyurl.com/4upqnd
def self.resolve(uri)
if uri.respond_to?(:scheme)
server = "#{uri.host}:#{uri.port || '11211'}"
options = parse_query(uri.query)
options.keys.each do |key|
value =
case value = options.delete(key)
when 'true' ; true
when 'false' ; false
else value.to_sym
end
options[key.to_sym] = value
end
options[:namespace] = uri.path.to_s.sub(/^\//, '')
new server, options
else
# if the object provided is not a URI, pass it straight through
# to the underlying implementation.
new uri
end
end
end
class Dalli < MemCacheBase
def initialize(server="localhost:11211", options={})
@cache =
if server.respond_to?(:stats)
server
else
require 'dalli'
::Dalli::Client.new(server, options)
end
end
def read(key)
key = hexdigest(key)
cache.get(key) || []
end
def write(key, entries)
key = hexdigest(key)
cache.set(key, entries)
end
def purge(key)
cache.delete(hexdigest(key))
nil
end
end
class MemCached < MemCacheBase
# The Memcached instance used to communicated with the memcached
# daemon.
attr_reader :cache
def initialize(server="localhost:11211", options={})
options[:prefix_key] ||= options.delete(:namespace) if options.key?(:namespace)
@cache =
if server.respond_to?(:stats)
server
else
require 'memcached'
Memcached.new(server, options)
end
end
def read(key)
key = hexdigest(key)
cache.get(key)
rescue Memcached::NotFound
[]
end
def write(key, entries)
key = hexdigest(key)
cache.set(key, entries)
end
def purge(key)
key = hexdigest(key)
cache.delete(key)
nil
rescue Memcached::NotFound
nil
end
end
MEMCACHE =
if defined?(::Memcached)
MemCached
else
Dalli
end
MEMCACHED = MEMCACHE
class GAEStore < MetaStore
attr_reader :cache
def initialize(options = {})
require 'rack/cache/appengine'
@cache = Rack::Cache::AppEngine::MemCache.new(options)
end
def read(key)
key = hexdigest(key)
cache.get(key) || []
end
def write(key, entries)
key = hexdigest(key)
cache.put(key, entries)
end
def purge(key)
key = hexdigest(key)
cache.delete(key)
nil
end
def self.resolve(uri)
self.new(:namespace => uri.host)
end
end
GAECACHE = GAEStore
GAE = GAEStore
end
end
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