class Rack::Session::Memcache

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.

Note that memcache does drop data before it may be listed to expire. For a full description of behaviour, please see memcache's documentation.

Constants

DEFAULT_OPTIONS

Attributes

mutex[R]
pool[R]

Public Class Methods

new(app, options={}) click to toggle source
Calls superclass method Rack::Session::Abstract::Persisted.new
# File lib/rack/session/memcache.rb, line 29
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 = options[:cache] || MemCache.new(mserv, mopts)
  unless @pool.active? and @pool.servers.any?(&:alive?)
    raise 'No memcache servers'
  end
end

Public Instance Methods

delete_session(req, session_id, options) click to toggle source
# File lib/rack/session/memcache.rb, line 71
def delete_session(req, session_id, options)
  with_lock(req) do
    @pool.delete(session_id.public_id)
    @pool.delete(session_id.private_id)
    generate_sid unless options[:drop]
  end
end
find_session(req, sid) click to toggle source
# File lib/rack/session/memcache.rb, line 49
def find_session(req, sid)
  with_lock(req) do
    unless sid and session = get_session_with_fallback(sid)
      sid, session = generate_sid, {}
      unless /^STORED/ =~ @pool.add(sid.private_id, session)
        raise "Session collision on '#{sid.inspect}'"
      end
    end
    [sid, session]
  end
end
generate_sid() click to toggle source
# File lib/rack/session/memcache.rb, line 42
def generate_sid
  loop do
    sid = super
    break sid unless @pool.get(sid.private_id, true)
  end
end
with_lock(req) { || ... } click to toggle source
# File lib/rack/session/memcache.rb, line 79
def with_lock(req)
  @mutex.lock if req.multithread?
  yield
rescue MemCache::MemCacheError, Errno::ECONNREFUSED
  if $VERBOSE
    warn "#{self} is unable to find memcached server."
    warn $!.inspect
  end
  raise
ensure
  @mutex.unlock if @mutex.locked?
end
write_session(req, session_id, new_session, options) click to toggle source
# File lib/rack/session/memcache.rb, line 61
def write_session(req, session_id, new_session, options)
  expiry = options[:expire_after]
  expiry = expiry.nil? ? 0 : expiry + 1

  with_lock(req) do
    @pool.set session_id.private_id, new_session, expiry
    session_id
  end
end

Private Instance Methods

get_session_with_fallback(sid) click to toggle source
# File lib/rack/session/memcache.rb, line 94
def get_session_with_fallback(sid)
  @pool.get(sid.private_id) || @pool.get(sid.public_id)
end