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# frozen_string_literal: true
require 'rack/session/abstract/id'
require 'dalli'
require 'connection_pool'
require 'English'
module Rack
module Session
# Rack::Session::Dalli provides memcached based session management.
class Dalli < Abstract::Persisted
attr_reader :pool
# Don't freeze this until we fix the specs/implementation
# rubocop:disable Style/MutableConstant
DEFAULT_DALLI_OPTIONS = {
namespace: 'rack:session',
memcache_server: 'localhost:11211'
}
# rubocop:enable Style/MutableConstant
# Brings in a new Rack::Session::Dalli middleware with the given
# `:memcache_server`. The server is either a hostname, or a
# host-with-port string in the form of "host_name:port", or an array of
# such strings. For example:
#
# use Rack::Session::Dalli,
# :memcache_server => "mc.example.com:1234"
#
# If no `:memcache_server` option is specified, Rack::Session::Dalli will
# connect to localhost, port 11211 (the default memcached port). If
# `:memcache_server` is set to nil, Dalli::Client will look for
# ENV['MEMCACHE_SERVERS'] and use that value if it is available, or fall
# back to the same default behavior described above.
#
# Rack::Session::Dalli is intended to be a drop-in replacement for
# Rack::Session::Memcache. It accepts additional options that control the
# behavior of Rack::Session, Dalli::Client, and an optional
# ConnectionPool. First and foremost, if you wish to instantiate your own
# Dalli::Client (or ConnectionPool) and use that instead of letting
# Rack::Session::Dalli instantiate it on your behalf, simply pass it in
# as the `:cache` option. Please note that you will be responsible for
# setting the namespace and any other options on Dalli::Client.
#
# Secondly, if you're not using the `:cache` option, Rack::Session::Dalli
# accepts the same options as Dalli::Client, so it's worth reviewing its
# documentation. Perhaps most importantly, if you don't specify a
# `:namespace` option, Rack::Session::Dalli will default to using
# "rack:session".
#
# Whether you are using the `:cache` option or not, it is not recommend
# to set `:expires_in`. Instead, use `:expire_after`, which will control
# both the expiration of the client cookie as well as the expiration of
# the corresponding entry in memcached.
#
# Rack::Session::Dalli also accepts a host of options that control how
# the sessions and session cookies are managed, including the
# aforementioned `:expire_after` option. Please see the documentation for
# Rack::Session::Abstract::Persisted for a detailed explanation of these
# options and their default values.
#
# Finally, if your web application is multithreaded, the
# Rack::Session::Dalli middleware can become a source of contention. You
# can use a connection pool of Dalli clients by passing in the
# `:pool_size` and/or `:pool_timeout` options. For example:
#
# use Rack::Session::Dalli,
# :memcache_server => "mc.example.com:1234",
# :pool_size => 10
#
# You must include the `connection_pool` gem in your project if you wish
# to use pool support. Please see the documentation for ConnectionPool
# for more information about it and its default options (which would only
# be applicable if you supplied one of the two options, but not both).
#
def initialize(app, options = {})
# Parent uses DEFAULT_OPTIONS to build @default_options for Rack::Session
super
# Determine the default TTL for newly-created sessions
@default_ttl = ttl @default_options[:expire_after]
# Normalize and validate passed options
mserv, mopts, popts = extract_dalli_options(options)
@pool = ConnectionPool.new(popts || {}) { ::Dalli::Client.new(mserv, mopts) }
end
def get_session(_env, sid)
with_block([nil, {}]) do |dc|
unless sid && !sid.empty? && (session = dc.get(sid))
old_sid = sid
sid = generate_sid_with(dc)
session = {}
unless dc.add(sid, session, @default_ttl)
sid = old_sid
redo # generate a new sid and try again
end
end
[sid, session]
end
end
def set_session(_env, session_id, new_session, options)
return false unless session_id
with_block(false) do |dc|
dc.set(session_id, new_session, ttl(options[:expire_after]))
session_id
end
end
def destroy_session(_env, session_id, options)
with_block do |dc|
dc.delete(session_id)
generate_sid_with(dc) unless options[:drop]
end
end
def find_session(req, sid)
get_session req.env, sid
end
def write_session(req, sid, session, options)
set_session req.env, sid, session, options
end
def delete_session(req, sid, options)
destroy_session req.env, sid, options
end
private
def extract_dalli_options(options)
raise 'Rack::Session::Dalli no longer supports the :cache option.' if options[:cache]
# Filter out Rack::Session-specific options and apply our defaults
# Filter out Rack::Session-specific options and apply our defaults
filtered_opts = options.reject { |k, _| DEFAULT_OPTIONS.key? k }
mopts = DEFAULT_DALLI_OPTIONS.merge(filtered_opts)
mserv = mopts.delete :memcache_server
popts = {}
if mopts[:pool_size] || mopts[:pool_timeout]
popts[:size] = mopts.delete :pool_size if mopts[:pool_size]
popts[:timeout] = mopts.delete :pool_timeout if mopts[:pool_timeout]
mopts[:threadsafe] = true
end
[mserv, mopts, popts]
end
def generate_sid_with(client)
loop do
sid = generate_sid
break sid unless client.get(sid)
end
end
def with_block(default = nil, &block)
@pool.with(&block)
rescue ::Dalli::DalliError, Errno::ECONNREFUSED
raise if /undefined class/.match?($ERROR_INFO.message)
if $VERBOSE
warn "#{self} is unable to find memcached server."
warn $ERROR_INFO.inspect
end
default
end
def ttl(expire_after)
expire_after.nil? ? 0 : expire_after + 1
end
end
end
end
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