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.



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# 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?{|c| c.alive? }
    raise 'No memcache servers'
  end
end

Instance Attribute Details

#mutex ⇒ Object (readonly)

Returns the value of attribute mutex.



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

def mutex
  @mutex
end

#pool ⇒ Object (readonly)

Returns the value of attribute pool.



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

def pool
  @pool
end

Instance Method Details

#destroy_session(env, session_id, options) ⇒ Object 



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# File 'lib/rack/session/memcache.rb', line 71

def destroy_session(env, session_id, options)
  with_lock(env) do
    @pool.delete(session_id)
    generate_sid unless options[:drop]
  end
end

#generate_sid ⇒ Object 



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# File 'lib/rack/session/memcache.rb', line 42

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

#get_session(env, sid) ⇒ Object 



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# File 'lib/rack/session/memcache.rb', line 49

def get_session(env, sid)
  with_lock(env, [nil, {}]) do
    unless sid and session = @pool.get(sid)
      sid, session = generate_sid, {}
      unless /^STORED/ =~ @pool.add(sid, session)
        raise "Session collision on '#{sid.inspect}'"
      end
    end
    [sid, session]
  end
end

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



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# File 'lib/rack/session/memcache.rb', line 61

def set_session(env, session_id, new_session, options)
  expiry = options[:expire_after]
  expiry = expiry.nil? ? 0 : expiry + 1

  with_lock(env, false) do
    @pool.set session_id, new_session, expiry
    session_id
  end
end

#with_lock(env, default = nil) ⇒ Object 



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# File 'lib/rack/session/memcache.rb', line 78

def with_lock(env, default=nil)
  @mutex.lock if env['rack.multithread']
  yield
rescue MemCache::MemCacheError, Errno::ECONNREFUSED
  if $VERBOSE
    warn "#{self} is unable to find memcached server."
    warn $!.inspect
  end
  default
ensure
  @mutex.unlock if @mutex.locked?
end