Class: Rack::Session::Memcache

Inherits:
Abstract::ID show all
Defined in:
lib/rack/session/memcache.rb

Overview

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.

Constant Summary collapse

DEFAULT_OPTIONS =
Abstract::ID::DEFAULT_OPTIONS.merge \
:namespace => 'rack:session',
:memcache_server => 'localhost:11211'

Instance Attribute Summary collapse

Attributes inherited from Abstract::ID

#default_options, #key

Instance Method Summary collapse

Methods inherited from Abstract::ID

#call, #context

Constructor Details

#initialize(app, options = {}) ⇒ Memcache

Returns a new instance of Memcache.



28
29
30
31
32
33
34
35
36
37
38
39
# File 'lib/rack/session/memcache.rb', line 28

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

Instance Attribute Details

#mutexObject (readonly)

Returns the value of attribute mutex.



23
24
25
# File 'lib/rack/session/memcache.rb', line 23

def mutex
  @mutex
end

#poolObject (readonly)

Returns the value of attribute pool.



23
24
25
# File 'lib/rack/session/memcache.rb', line 23

def pool
  @pool
end

Instance Method Details

#generate_sidObject



41
42
43
44
45
46
# File 'lib/rack/session/memcache.rb', line 41

def generate_sid
  loop do
    sid = super
    break sid unless @pool.get(sid, true)
  end
end

#get_session(env, session_id) ⇒ Object



48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
# File 'lib/rack/session/memcache.rb', line 48

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

#set_session(env, session_id, new_session, options) ⇒ Object



67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
# File 'lib/rack/session/memcache.rb', line 67

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