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# AUTHOR: blink <blinketje@gmail.com>; blink#ruby-lang@irc.freenode.net
require 'rack/session/abstract/id'
require 'memcache'
module Rack
module Session
# Rack::Session::Memcache provides simple cookie based session management.
# Session data is stored in memcached. The corresponding session key is
# maintained in the cookie.
# You may treat Session::Memcache as you would Session::Pool with the
# following caveats.
#
# * Setting :expire_after to 0 would note to the Memcache server to hang
# onto the session data until it would drop it according to it's own
# specifications. However, the cookie sent to the client would expire
# immediately.
#
# Note that memcache does drop data before it may be listed to expire. For
# a full description of behaviour, please see memcache's documentation.
class Memcache < Abstract::ID
attr_reader :mutex, :pool
DEFAULT_OPTIONS = Abstract::ID::DEFAULT_OPTIONS.merge \
:namespace => 'rack:session',
:memcache_server => 'localhost:11211'
def initialize(app, options={})
super
@mutex = Mutex.new
mserv = @default_options[:memcache_server]
mopts = @default_options.
reject{|k,v| MemCache::DEFAULT_OPTIONS.include? k }
@pool = MemCache.new mserv, mopts
unless @pool.active? and @pool.servers.any?{|c| c.alive? }
raise 'No memcache servers'
end
end
def generate_sid
loop do
sid = super
break sid unless @pool.get(sid, true)
end
end
def get_session(env, session_id)
@mutex.lock if env['rack.multithread']
unless session_id and session = @pool.get(session_id)
session_id, session = generate_sid, {}
unless /^STORED/ =~ @pool.add(session_id, session)
raise "Session collision on '#{session_id.inspect}'"
end
end
session.instance_variable_set '@old', @pool.get(session_id, true)
return [session_id, session]
rescue MemCache::MemCacheError, Errno::ECONNREFUSED
# MemCache server cannot be contacted
warn "#{self} is unable to find memcached server."
warn $!.inspect
return [ nil, {} ]
ensure
@mutex.unlock if @mutex.locked?
end
def set_session(env, session_id, new_session, options)
expiry = options[:expire_after]
expiry = expiry.nil? ? 0 : expiry + 1
@mutex.lock if env['rack.multithread']
if options[:renew] or options[:drop]
@pool.delete session_id
return false if options[:drop]
session_id = generate_sid
@pool.add session_id, {} # so we don't worry about cache miss on #set
end
session = @pool.get(session_id) || {}
old_session = new_session.instance_variable_get '@old'
old_session = old_session ? Marshal.load(old_session) : {}
unless Hash === old_session and Hash === new_session
env['rack.errors'].
puts 'Bad old_session or new_session sessions provided.'
else # merge sessions
# alterations are either update or delete, making as few changes as
# possible to prevent possible issues.
# removed keys
delete = old_session.keys - new_session.keys
if $VERBOSE and not delete.empty?
env['rack.errors'].
puts "//@#{session_id}: delete #{delete*','}"
end
delete.each{|k| session.delete k }
# added or altered keys
update = new_session.keys.
select{|k| new_session[k] != old_session[k] }
if $VERBOSE and not update.empty?
env['rack.errors'].puts "//@#{session_id}: update #{update*','}"
end
update.each{|k| session[k] = new_session[k] }
end
@pool.set session_id, session, expiry
return session_id
rescue MemCache::MemCacheError, Errno::ECONNREFUSED
# MemCache server cannot be contacted
warn "#{self} is unable to find memcached server."
warn $!.inspect
return false
ensure
@mutex.unlock if @mutex.locked?
end
end
end
end
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