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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
@pool = MemCache.
new @default_options[:memcache_server], @default_options
raise 'No memcache servers' unless @pool.servers.any?{|s|s.alive?}
end
def generate_sid
loop do
sid = super
break sid unless @pool.get(sid, true)
end
end
def get_session(env, sid)
session = @pool.get(sid) if sid
@mutex.lock if env['rack.multithread']
unless sid and session
env['rack.errors'].puts("Session '#{sid.inspect}' not found, initializing...") if $VERBOSE and not sid.nil?
session = {}
sid = generate_sid
ret = @pool.add sid, session
raise "Session collision on '#{sid.inspect}'" unless /^STORED/ =~ ret
end
session.instance_variable_set('@old', {}.merge(session))
return [sid, session]
rescue MemCache::MemCacheError, Errno::ECONNREFUSED # MemCache server cannot be contacted
warn "#{self} is unable to find server."
warn $!.inspect
return [ nil, {} ]
ensure
@mutex.unlock if env['rack.multithread']
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']
session = @pool.get(session_id) || {}
if options[:renew] or options[:drop]
@pool.delete session_id
return false if options[:drop]
session_id = generate_sid
@pool.add session_id, 0 # so we don't worry about cache miss on #set
end
old_session = new_session.instance_variable_get('@old') || {}
session = merge_sessions session_id, old_session, new_session, session
@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 server."
warn $!.inspect
return false
ensure
@mutex.unlock if env['rack.multithread']
end
private
def merge_sessions sid, old, new, cur=nil
cur ||= {}
unless Hash === old and Hash === new
warn 'Bad old or new sessions provided.'
return cur
end
delete = old.keys - new.keys
warn "//@#{sid}: delete #{delete*','}" if $VERBOSE and not delete.empty?
delete.each{|k| cur.delete k }
update = new.keys.select{|k| new[k] != old[k] }
warn "//@#{sid}: update #{update*','}" if $VERBOSE and not update.empty?
update.each{|k| cur[k] = new[k] }
cur
end
end
end
end
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