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# frozen_string_literal: false
#
# = drb/drb.rb
#
# Distributed Ruby: _dRuby_ version 2.0.4
#
# Copyright (c) 1999-2003 Masatoshi SEKI. You can redistribute it and/or
# modify it under the same terms as Ruby.
#
# Author:: Masatoshi SEKI
#
# Documentation:: William Webber (william@williamwebber.com)
#
# == Overview
#
# dRuby is a distributed object system for Ruby. It allows an object in one
# Ruby process to invoke methods on an object in another Ruby process on the
# same or a different machine.
#
# The Ruby standard library contains the core classes of the dRuby package.
# However, the full package also includes access control lists and the
# Rinda tuple-space distributed task management system, as well as a
# large number of samples. The full dRuby package can be downloaded from
# the dRuby home page (see *References*).
#
# For an introduction and examples of usage see the documentation to the
# DRb module.
#
# == References
#
# [http://www2a.biglobe.ne.jp/~seki/ruby/druby.html]
# The dRuby home page, in Japanese. Contains the full dRuby package
# and links to other Japanese-language sources.
#
# [http://www2a.biglobe.ne.jp/~seki/ruby/druby.en.html]
# The English version of the dRuby home page.
#
# [http://pragprog.com/book/sidruby/the-druby-book]
# The dRuby Book: Distributed and Parallel Computing with Ruby
# by Masatoshi Seki and Makoto Inoue
#
# [http://www.ruby-doc.org/docs/ProgrammingRuby/html/ospace.html]
# The chapter from *Programming* *Ruby* by Dave Thomas and Andy Hunt
# which discusses dRuby.
#
# [http://www.clio.ne.jp/home/web-i31s/Flotuard/Ruby/PRC2K_seki/dRuby.en.html]
# Translation of presentation on Ruby by Masatoshi Seki.
require 'socket'
require 'io/wait'
require 'monitor'
require_relative 'eq'
#
# == Overview
#
# dRuby is a distributed object system for Ruby. It is written in
# pure Ruby and uses its own protocol. No add-in services are needed
# beyond those provided by the Ruby runtime, such as TCP sockets. It
# does not rely on or interoperate with other distributed object
# systems such as CORBA, RMI, or .NET.
#
# dRuby allows methods to be called in one Ruby process upon a Ruby
# object located in another Ruby process, even on another machine.
# References to objects can be passed between processes. Method
# arguments and return values are dumped and loaded in marshalled
# format. All of this is done transparently to both the caller of the
# remote method and the object that it is called upon.
#
# An object in a remote process is locally represented by a
# DRb::DRbObject instance. This acts as a sort of proxy for the
# remote object. Methods called upon this DRbObject instance are
# forwarded to its remote object. This is arranged dynamically at run
# time. There are no statically declared interfaces for remote
# objects, such as CORBA's IDL.
#
# dRuby calls made into a process are handled by a DRb::DRbServer
# instance within that process. This reconstitutes the method call,
# invokes it upon the specified local object, and returns the value to
# the remote caller. Any object can receive calls over dRuby. There
# is no need to implement a special interface, or mixin special
# functionality. Nor, in the general case, does an object need to
# explicitly register itself with a DRbServer in order to receive
# dRuby calls.
#
# One process wishing to make dRuby calls upon another process must
# somehow obtain an initial reference to an object in the remote
# process by some means other than as the return value of a remote
# method call, as there is initially no remote object reference it can
# invoke a method upon. This is done by attaching to the server by
# URI. Each DRbServer binds itself to a URI such as
# 'druby://example.com:8787'. A DRbServer can have an object attached
# to it that acts as the server's *front* *object*. A DRbObject can
# be explicitly created from the server's URI. This DRbObject's
# remote object will be the server's front object. This front object
# can then return references to other Ruby objects in the DRbServer's
# process.
#
# Method calls made over dRuby behave largely the same as normal Ruby
# method calls made within a process. Method calls with blocks are
# supported, as are raising exceptions. In addition to a method's
# standard errors, a dRuby call may also raise one of the
# dRuby-specific errors, all of which are subclasses of DRb::DRbError.
#
# Any type of object can be passed as an argument to a dRuby call or
# returned as its return value. By default, such objects are dumped
# or marshalled at the local end, then loaded or unmarshalled at the
# remote end. The remote end therefore receives a copy of the local
# object, not a distributed reference to it; methods invoked upon this
# copy are executed entirely in the remote process, not passed on to
# the local original. This has semantics similar to pass-by-value.
#
# However, if an object cannot be marshalled, a dRuby reference to it
# is passed or returned instead. This will turn up at the remote end
# as a DRbObject instance. All methods invoked upon this remote proxy
# are forwarded to the local object, as described in the discussion of
# DRbObjects. This has semantics similar to the normal Ruby
# pass-by-reference.
#
# The easiest way to signal that we want an otherwise marshallable
# object to be passed or returned as a DRbObject reference, rather
# than marshalled and sent as a copy, is to include the
# DRb::DRbUndumped mixin module.
#
# dRuby supports calling remote methods with blocks. As blocks (or
# rather the Proc objects that represent them) are not marshallable,
# the block executes in the local, not the remote, context. Each
# value yielded to the block is passed from the remote object to the
# local block, then the value returned by each block invocation is
# passed back to the remote execution context to be collected, before
# the collected values are finally returned to the local context as
# the return value of the method invocation.
#
# == Examples of usage
#
# For more dRuby samples, see the +samples+ directory in the full
# dRuby distribution.
#
# === dRuby in client/server mode
#
# This illustrates setting up a simple client-server drb
# system. Run the server and client code in different terminals,
# starting the server code first.
#
# ==== Server code
#
# require 'drb/drb'
#
# # The URI for the server to connect to
# URI="druby://localhost:8787"
#
# class TimeServer
#
# def get_current_time
# return Time.now
# end
#
# end
#
# # The object that handles requests on the server
# FRONT_OBJECT=TimeServer.new
#
# DRb.start_service(URI, FRONT_OBJECT)
# # Wait for the drb server thread to finish before exiting.
# DRb.thread.join
#
# ==== Client code
#
# require 'drb/drb'
#
# # The URI to connect to
# SERVER_URI="druby://localhost:8787"
#
# # Start a local DRbServer to handle callbacks.
# #
# # Not necessary for this small example, but will be required
# # as soon as we pass a non-marshallable object as an argument
# # to a dRuby call.
# #
# # Note: this must be called at least once per process to take any effect.
# # This is particularly important if your application forks.
# DRb.start_service
#
# timeserver = DRbObject.new_with_uri(SERVER_URI)
# puts timeserver.get_current_time
#
# === Remote objects under dRuby
#
# This example illustrates returning a reference to an object
# from a dRuby call. The Logger instances live in the server
# process. References to them are returned to the client process,
# where methods can be invoked upon them. These methods are
# executed in the server process.
#
# ==== Server code
#
# require 'drb/drb'
#
# URI="druby://localhost:8787"
#
# class Logger
#
# # Make dRuby send Logger instances as dRuby references,
# # not copies.
# include DRb::DRbUndumped
#
# def initialize(n, fname)
# @name = n
# @filename = fname
# end
#
# def log(message)
# File.open(@filename, "a") do |f|
# f.puts("#{Time.now}: #{@name}: #{message}")
# end
# end
#
# end
#
# # We have a central object for creating and retrieving loggers.
# # This retains a local reference to all loggers created. This
# # is so an existing logger can be looked up by name, but also
# # to prevent loggers from being garbage collected. A dRuby
# # reference to an object is not sufficient to prevent it being
# # garbage collected!
# class LoggerFactory
#
# def initialize(bdir)
# @basedir = bdir
# @loggers = {}
# end
#
# def get_logger(name)
# if !@loggers.has_key? name
# # make the filename safe, then declare it to be so
# fname = name.gsub(/[.\/\\\:]/, "_")
# @loggers[name] = Logger.new(name, @basedir + "/" + fname)
# end
# return @loggers[name]
# end
#
# end
#
# FRONT_OBJECT=LoggerFactory.new("/tmp/dlog")
#
# DRb.start_service(URI, FRONT_OBJECT)
# DRb.thread.join
#
# ==== Client code
#
# require 'drb/drb'
#
# SERVER_URI="druby://localhost:8787"
#
# DRb.start_service
#
# log_service=DRbObject.new_with_uri(SERVER_URI)
#
# ["loga", "logb", "logc"].each do |logname|
#
# logger=log_service.get_logger(logname)
#
# logger.log("Hello, world!")
# logger.log("Goodbye, world!")
# logger.log("=== EOT ===")
#
# end
#
# == Security
#
# As with all network services, security needs to be considered when
# using dRuby. By allowing external access to a Ruby object, you are
# not only allowing outside clients to call the methods you have
# defined for that object, but by default to execute arbitrary Ruby
# code on your server. Consider the following:
#
# # !!! UNSAFE CODE !!!
# ro = DRbObject::new_with_uri("druby://your.server.com:8989")
# class << ro
# undef :instance_eval # force call to be passed to remote object
# end
# ro.instance_eval("`rm -rf *`")
#
# The dangers posed by instance_eval and friends are such that a
# DRbServer should only be used when clients are trusted.
#
# A DRbServer can be configured with an access control list to
# selectively allow or deny access from specified IP addresses. The
# main druby distribution provides the ACL class for this purpose. In
# general, this mechanism should only be used alongside, rather than
# as a replacement for, a good firewall.
#
# == dRuby internals
#
# dRuby is implemented using three main components: a remote method
# call marshaller/unmarshaller; a transport protocol; and an
# ID-to-object mapper. The latter two can be directly, and the first
# indirectly, replaced, in order to provide different behaviour and
# capabilities.
#
# Marshalling and unmarshalling of remote method calls is performed by
# a DRb::DRbMessage instance. This uses the Marshal module to dump
# the method call before sending it over the transport layer, then
# reconstitute it at the other end. There is normally no need to
# replace this component, and no direct way is provided to do so.
# However, it is possible to implement an alternative marshalling
# scheme as part of an implementation of the transport layer.
#
# The transport layer is responsible for opening client and server
# network connections and forwarding dRuby request across them.
# Normally, it uses DRb::DRbMessage internally to manage marshalling
# and unmarshalling. The transport layer is managed by
# DRb::DRbProtocol. Multiple protocols can be installed in
# DRbProtocol at the one time; selection between them is determined by
# the scheme of a dRuby URI. The default transport protocol is
# selected by the scheme 'druby:', and implemented by
# DRb::DRbTCPSocket. This uses plain TCP/IP sockets for
# communication. An alternative protocol, using UNIX domain sockets,
# is implemented by DRb::DRbUNIXSocket in the file drb/unix.rb, and
# selected by the scheme 'drbunix:'. A sample implementation over
# HTTP can be found in the samples accompanying the main dRuby
# distribution.
#
# The ID-to-object mapping component maps dRuby object ids to the
# objects they refer to, and vice versa. The implementation to use
# can be specified as part of a DRb::DRbServer's configuration. The
# default implementation is provided by DRb::DRbIdConv. It uses an
# object's ObjectSpace id as its dRuby id. This means that the dRuby
# reference to that object only remains meaningful for the lifetime of
# the object's process and the lifetime of the object within that
# process. A modified implementation is provided by DRb::TimerIdConv
# in the file drb/timeridconv.rb. This implementation retains a local
# reference to all objects exported over dRuby for a configurable
# period of time (defaulting to ten minutes), to prevent them being
# garbage-collected within this time. Another sample implementation
# is provided in sample/name.rb in the main dRuby distribution. This
# allows objects to specify their own id or "name". A dRuby reference
# can be made persistent across processes by having each process
# register an object using the same dRuby name.
#
module DRb
# Superclass of all errors raised in the DRb module.
class DRbError < RuntimeError; end
# Error raised when an error occurs on the underlying communication
# protocol.
class DRbConnError < DRbError; end
# Class responsible for converting between an object and its id.
#
# This, the default implementation, uses an object's local ObjectSpace
# __id__ as its id. This means that an object's identification over
# drb remains valid only while that object instance remains alive
# within the server runtime.
#
# For alternative mechanisms, see DRb::TimerIdConv in drb/timeridconv.rb
# and DRbNameIdConv in sample/name.rb in the full drb distribution.
class DRbIdConv
# Convert an object reference id to an object.
#
# This implementation looks up the reference id in the local object
# space and returns the object it refers to.
def to_obj(ref)
ObjectSpace._id2ref(ref)
end
# Convert an object into a reference id.
#
# This implementation returns the object's __id__ in the local
# object space.
def to_id(obj)
case obj
when Object
obj.nil? ? nil : obj.__id__
when BasicObject
obj.__id__
end
end
end
# Mixin module making an object undumpable or unmarshallable.
#
# If an object which includes this module is returned by method
# called over drb, then the object remains in the server space
# and a reference to the object is returned, rather than the
# object being marshalled and moved into the client space.
module DRbUndumped
def _dump(dummy) # :nodoc:
raise TypeError, 'can\'t dump'
end
end
# Error raised by the DRb module when an attempt is made to refer to
# the context's current drb server but the context does not have one.
# See #current_server.
class DRbServerNotFound < DRbError; end
# Error raised by the DRbProtocol module when it cannot find any
# protocol implementation support the scheme specified in a URI.
class DRbBadURI < DRbError; end
# Error raised by a dRuby protocol when it doesn't support the
# scheme specified in a URI. See DRb::DRbProtocol.
class DRbBadScheme < DRbError; end
# An exception wrapping a DRb::DRbUnknown object
class DRbUnknownError < DRbError
# Create a new DRbUnknownError for the DRb::DRbUnknown object +unknown+
def initialize(unknown)
@unknown = unknown
super(unknown.name)
end
# Get the wrapped DRb::DRbUnknown object.
attr_reader :unknown
def self._load(s) # :nodoc:
Marshal::load(s)
end
def _dump(lv) # :nodoc:
Marshal::dump(@unknown)
end
end
# An exception wrapping an error object
class DRbRemoteError < DRbError
# Creates a new remote error that wraps the Exception +error+
def initialize(error)
@reason = error.class.to_s
super("#{error.message} (#{error.class})")
set_backtrace(error.backtrace)
end
# the class of the error, as a string.
attr_reader :reason
end
# Class wrapping a marshalled object whose type is unknown locally.
#
# If an object is returned by a method invoked over drb, but the
# class of the object is unknown in the client namespace, or
# the object is a constant unknown in the client namespace, then
# the still-marshalled object is returned wrapped in a DRbUnknown instance.
#
# If this object is passed as an argument to a method invoked over
# drb, then the wrapped object is passed instead.
#
# The class or constant name of the object can be read from the
# +name+ attribute. The marshalled object is held in the +buf+
# attribute.
class DRbUnknown
# Create a new DRbUnknown object.
#
# +buf+ is a string containing a marshalled object that could not
# be unmarshalled. +err+ is the error message that was raised
# when the unmarshalling failed. It is used to determine the
# name of the unmarshalled object.
def initialize(err, buf)
case err.to_s
when /uninitialized constant (\S+)/
@name = $1
when /undefined class\/module (\S+)/
@name = $1
else
@name = nil
end
@buf = buf
end
# The name of the unknown thing.
#
# Class name for unknown objects; variable name for unknown
# constants.
attr_reader :name
# Buffer contained the marshalled, unknown object.
attr_reader :buf
def self._load(s) # :nodoc:
begin
Marshal::load(s)
rescue NameError, ArgumentError
DRbUnknown.new($!, s)
end
end
def _dump(lv) # :nodoc:
@buf
end
# Attempt to load the wrapped marshalled object again.
#
# If the class of the object is now known locally, the object
# will be unmarshalled and returned. Otherwise, a new
# but identical DRbUnknown object will be returned.
def reload
self.class._load(@buf)
end
# Create a DRbUnknownError exception containing this object.
def exception
DRbUnknownError.new(self)
end
end
# An Array wrapper that can be sent to another server via DRb.
#
# All entries in the array will be dumped or be references that point to
# the local server.
class DRbArray
# Creates a new DRbArray that either dumps or wraps all the items in the
# Array +ary+ so they can be loaded by a remote DRb server.
def initialize(ary)
@ary = ary.collect { |obj|
if obj.kind_of? DRbUndumped
DRbObject.new(obj)
else
begin
Marshal.dump(obj)
obj
rescue
DRbObject.new(obj)
end
end
}
end
def self._load(s) # :nodoc:
Marshal::load(s)
end
def _dump(lv) # :nodoc:
Marshal.dump(@ary)
end
end
# Handler for sending and receiving drb messages.
#
# This takes care of the low-level marshalling and unmarshalling
# of drb requests and responses sent over the wire between server
# and client. This relieves the implementor of a new drb
# protocol layer with having to deal with these details.
#
# The user does not have to directly deal with this object in
# normal use.
class DRbMessage
def initialize(config) # :nodoc:
@load_limit = config[:load_limit]
@argc_limit = config[:argc_limit]
end
def dump(obj, error=false) # :nodoc:
case obj
when DRbUndumped
obj = make_proxy(obj, error)
when Object
# nothing
else
obj = make_proxy(obj, error)
end
begin
str = Marshal::dump(obj)
rescue
str = Marshal::dump(make_proxy(obj, error))
end
[str.size].pack('N') + str
end
def load(soc) # :nodoc:
begin
sz = soc.read(4) # sizeof (N)
rescue
raise(DRbConnError, $!.message, $!.backtrace)
end
raise(DRbConnError, 'connection closed') if sz.nil?
raise(DRbConnError, 'premature header') if sz.size < 4
sz = sz.unpack('N')[0]
raise(DRbConnError, "too large packet #{sz}") if @load_limit < sz
begin
str = soc.read(sz)
rescue
raise(DRbConnError, $!.message, $!.backtrace)
end
raise(DRbConnError, 'connection closed') if str.nil?
raise(DRbConnError, 'premature marshal format(can\'t read)') if str.size < sz
DRb.mutex.synchronize do
begin
Marshal::load(str)
rescue NameError, ArgumentError
DRbUnknown.new($!, str)
end
end
end
def send_request(stream, ref, msg_id, arg, b) # :nodoc:
ary = []
ary.push(dump(ref.__drbref))
ary.push(dump(msg_id.id2name))
ary.push(dump(arg.length))
arg.each do |e|
ary.push(dump(e))
end
ary.push(dump(b))
stream.write(ary.join(''))
rescue
raise(DRbConnError, $!.message, $!.backtrace)
end
def recv_request(stream) # :nodoc:
ref = load(stream)
ro = DRb.to_obj(ref)
msg = load(stream)
argc = load(stream)
raise(DRbConnError, "too many arguments") if @argc_limit < argc
argv = Array.new(argc, nil)
argc.times do |n|
argv[n] = load(stream)
end
block = load(stream)
return ro, msg, argv, block
end
def send_reply(stream, succ, result) # :nodoc:
stream.write(dump(succ) + dump(result, !succ))
rescue
raise(DRbConnError, $!.message, $!.backtrace)
end
def recv_reply(stream) # :nodoc:
succ = load(stream)
result = load(stream)
[succ, result]
end
private
def make_proxy(obj, error=false) # :nodoc:
if error
DRbRemoteError.new(obj)
else
DRbObject.new(obj)
end
end
end
# Module managing the underlying network protocol(s) used by drb.
#
# By default, drb uses the DRbTCPSocket protocol. Other protocols
# can be defined. A protocol must define the following class methods:
#
# [open(uri, config)] Open a client connection to the server at +uri+,
# using configuration +config+. Return a protocol
# instance for this connection.
# [open_server(uri, config)] Open a server listening at +uri+,
# using configuration +config+. Return a
# protocol instance for this listener.
# [uri_option(uri, config)] Take a URI, possibly containing an option
# component (e.g. a trailing '?param=val'),
# and return a [uri, option] tuple.
#
# All of these methods should raise a DRbBadScheme error if the URI
# does not identify the protocol they support (e.g. "druby:" for
# the standard Ruby protocol). This is how the DRbProtocol module,
# given a URI, determines which protocol implementation serves that
# protocol.
#
# The protocol instance returned by #open_server must have the
# following methods:
#
# [accept] Accept a new connection to the server. Returns a protocol
# instance capable of communicating with the client.
# [close] Close the server connection.
# [uri] Get the URI for this server.
#
# The protocol instance returned by #open must have the following methods:
#
# [send_request (ref, msg_id, arg, b)]
# Send a request to +ref+ with the given message id and arguments.
# This is most easily implemented by calling DRbMessage.send_request,
# providing a stream that sits on top of the current protocol.
# [recv_reply]
# Receive a reply from the server and return it as a [success-boolean,
# reply-value] pair. This is most easily implemented by calling
# DRb.recv_reply, providing a stream that sits on top of the
# current protocol.
# [alive?]
# Is this connection still alive?
# [close]
# Close this connection.
#
# The protocol instance returned by #open_server().accept() must have
# the following methods:
#
# [recv_request]
# Receive a request from the client and return a [object, message,
# args, block] tuple. This is most easily implemented by calling
# DRbMessage.recv_request, providing a stream that sits on top of
# the current protocol.
# [send_reply(succ, result)]
# Send a reply to the client. This is most easily implemented
# by calling DRbMessage.send_reply, providing a stream that sits
# on top of the current protocol.
# [close]
# Close this connection.
#
# A new protocol is registered with the DRbProtocol module using
# the add_protocol method.
#
# For examples of other protocols, see DRbUNIXSocket in drb/unix.rb,
# and HTTP0 in sample/http0.rb and sample/http0serv.rb in the full
# drb distribution.
module DRbProtocol
# Add a new protocol to the DRbProtocol module.
def add_protocol(prot)
@protocol.push(prot)
end
module_function :add_protocol
# Open a client connection to +uri+ with the configuration +config+.
#
# The DRbProtocol module asks each registered protocol in turn to
# try to open the URI. Each protocol signals that it does not handle that
# URI by raising a DRbBadScheme error. If no protocol recognises the
# URI, then a DRbBadURI error is raised. If a protocol accepts the
# URI, but an error occurs in opening it, a DRbConnError is raised.
def open(uri, config, first=true)
@protocol.each do |prot|
begin
return prot.open(uri, config)
rescue DRbBadScheme
rescue DRbConnError
raise($!)
rescue
raise(DRbConnError, "#{uri} - #{$!.inspect}")
end
end
if first && (config[:auto_load] != false)
auto_load(uri)
return open(uri, config, false)
end
raise DRbBadURI, 'can\'t parse uri:' + uri
end
module_function :open
# Open a server listening for connections at +uri+ with
# configuration +config+.
#
# The DRbProtocol module asks each registered protocol in turn to
# try to open a server at the URI. Each protocol signals that it does
# not handle that URI by raising a DRbBadScheme error. If no protocol
# recognises the URI, then a DRbBadURI error is raised. If a protocol
# accepts the URI, but an error occurs in opening it, the underlying
# error is passed on to the caller.
def open_server(uri, config, first=true)
@protocol.each do |prot|
begin
return prot.open_server(uri, config)
rescue DRbBadScheme
end
end
if first && (config[:auto_load] != false)
auto_load(uri)
return open_server(uri, config, false)
end
raise DRbBadURI, 'can\'t parse uri:' + uri
end
module_function :open_server
# Parse +uri+ into a [uri, option] pair.
#
# The DRbProtocol module asks each registered protocol in turn to
# try to parse the URI. Each protocol signals that it does not handle that
# URI by raising a DRbBadScheme error. If no protocol recognises the
# URI, then a DRbBadURI error is raised.
def uri_option(uri, config, first=true)
@protocol.each do |prot|
begin
uri, opt = prot.uri_option(uri, config)
# opt = nil if opt == ''
return uri, opt
rescue DRbBadScheme
end
end
if first && (config[:auto_load] != false)
auto_load(uri)
return uri_option(uri, config, false)
end
raise DRbBadURI, 'can\'t parse uri:' + uri
end
module_function :uri_option
def auto_load(uri) # :nodoc:
if /\Adrb([a-z0-9]+):/ =~ uri
require("drb/#{$1}") rescue nil
end
end
module_function :auto_load
end
# The default drb protocol which communicates over a TCP socket.
#
# The DRb TCP protocol URI looks like:
# <code>druby://<host>:<port>?<option></code>. The option is optional.
class DRbTCPSocket
# :stopdoc:
private
def self.parse_uri(uri)
if /\Adruby:\/\/(.*?):(\d+)(\?(.*))?\z/ =~ uri
host = $1
port = $2.to_i
option = $4
[host, port, option]
else
raise(DRbBadScheme, uri) unless uri.start_with?('druby:')
raise(DRbBadURI, 'can\'t parse uri:' + uri)
end
end
public
# Open a client connection to +uri+ (DRb URI string) using configuration
# +config+.
#
# This can raise DRb::DRbBadScheme or DRb::DRbBadURI if +uri+ is not for a
# recognized protocol. See DRb::DRbServer.new for information on built-in
# URI protocols.
def self.open(uri, config)
host, port, = parse_uri(uri)
soc = TCPSocket.open(host, port)
self.new(uri, soc, config)
end
# Returns the hostname of this server
def self.getservername
host = Socket::gethostname
begin
Socket::getaddrinfo(host, nil,
Socket::AF_UNSPEC,
Socket::SOCK_STREAM,
0,
Socket::AI_PASSIVE)[0][3]
rescue
'localhost'
end
end
# For the families available for +host+, returns a TCPServer on +port+.
# If +port+ is 0 the first available port is used. IPv4 servers are
# preferred over IPv6 servers.
def self.open_server_inaddr_any(host, port)
infos = Socket::getaddrinfo(host, nil,
Socket::AF_UNSPEC,
Socket::SOCK_STREAM,
0,
Socket::AI_PASSIVE)
families = Hash[*infos.collect { |af, *_| af }.uniq.zip([]).flatten]
return TCPServer.open('0.0.0.0', port) if families.has_key?('AF_INET')
return TCPServer.open('::', port) if families.has_key?('AF_INET6')
return TCPServer.open(port)
# :stopdoc:
end
# Open a server listening for connections at +uri+ using
# configuration +config+.
def self.open_server(uri, config)
uri = 'druby://:0' unless uri
host, port, _ = parse_uri(uri)
config = {:tcp_original_host => host}.update(config)
if host.size == 0
host = getservername
soc = open_server_inaddr_any(host, port)
else
soc = TCPServer.open(host, port)
end
port = soc.addr[1] if port == 0
config[:tcp_port] = port
uri = "druby://#{host}:#{port}"
self.new(uri, soc, config)
end
# Parse +uri+ into a [uri, option] pair.
def self.uri_option(uri, config)
host, port, option = parse_uri(uri)
return "druby://#{host}:#{port}", option
end
# Create a new DRbTCPSocket instance.
#
# +uri+ is the URI we are connected to.
# +soc+ is the tcp socket we are bound to. +config+ is our
# configuration.
def initialize(uri, soc, config={})
@uri = uri
@socket = soc
@config = config
@acl = config[:tcp_acl]
@msg = DRbMessage.new(config)
set_sockopt(@socket)
@shutdown_pipe_r, @shutdown_pipe_w = IO.pipe
end
# Get the URI that we are connected to.
attr_reader :uri
# Get the address of our TCP peer (the other end of the socket
# we are bound to.
def peeraddr
@socket.peeraddr
end
# Get the socket.
def stream; @socket; end
# On the client side, send a request to the server.
def send_request(ref, msg_id, arg, b)
@msg.send_request(stream, ref, msg_id, arg, b)
end
# On the server side, receive a request from the client.
def recv_request
@msg.recv_request(stream)
end
# On the server side, send a reply to the client.
def send_reply(succ, result)
@msg.send_reply(stream, succ, result)
end
# On the client side, receive a reply from the server.
def recv_reply
@msg.recv_reply(stream)
end
public
# Close the connection.
#
# If this is an instance returned by #open_server, then this stops
# listening for new connections altogether. If this is an instance
# returned by #open or by #accept, then it closes this particular
# client-server session.
def close
shutdown
if @socket
@socket.close
@socket = nil
end
close_shutdown_pipe
end
def close_shutdown_pipe
@shutdown_pipe_w.close
@shutdown_pipe_r.close
end
private :close_shutdown_pipe
# On the server side, for an instance returned by #open_server,
# accept a client connection and return a new instance to handle
# the server's side of this client-server session.
def accept
while true
s = accept_or_shutdown
return nil unless s
break if (@acl ? @acl.allow_socket?(s) : true)
s.close
end
if @config[:tcp_original_host].to_s.size == 0
uri = "druby://#{s.addr[3]}:#{@config[:tcp_port]}"
else
uri = @uri
end
self.class.new(uri, s, @config)
end
def accept_or_shutdown
readables, = IO.select([@socket, @shutdown_pipe_r])
if readables.include? @shutdown_pipe_r
return nil
end
@socket.accept
end
private :accept_or_shutdown
# Graceful shutdown
def shutdown
@shutdown_pipe_w.close
end
# Check to see if this connection is alive.
def alive?
return false unless @socket
if @socket.to_io.wait_readable(0)
close
return false
end
true
end
def set_sockopt(soc) # :nodoc:
soc.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
rescue IOError, Errno::ECONNRESET, Errno::EINVAL
# closed/shutdown socket, ignore error
end
end
module DRbProtocol
@protocol = [DRbTCPSocket] # default
end
class DRbURIOption # :nodoc: I don't understand the purpose of this class...
def initialize(option)
@option = option.to_s
end
attr_reader :option
def to_s; @option; end
def ==(other)
return false unless DRbURIOption === other
@option == other.option
end
def hash
@option.hash
end
alias eql? ==
end
# Object wrapping a reference to a remote drb object.
#
# Method calls on this object are relayed to the remote
# object that this object is a stub for.
class DRbObject
# Unmarshall a marshalled DRbObject.
#
# If the referenced object is located within the local server, then
# the object itself is returned. Otherwise, a new DRbObject is
# created to act as a stub for the remote referenced object.
def self._load(s)
uri, ref = Marshal.load(s)
if DRb.here?(uri)
obj = DRb.to_obj(ref)
return obj
end
self.new_with(uri, ref)
end
# Creates a DRb::DRbObject given the reference information to the remote
# host +uri+ and object +ref+.
def self.new_with(uri, ref)
it = self.allocate
it.instance_variable_set(:@uri, uri)
it.instance_variable_set(:@ref, ref)
it
end
# Create a new DRbObject from a URI alone.
def self.new_with_uri(uri)
self.new(nil, uri)
end
# Marshall this object.
#
# The URI and ref of the object are marshalled.
def _dump(lv)
Marshal.dump([@uri, @ref])
end
# Create a new remote object stub.
#
# +obj+ is the (local) object we want to create a stub for. Normally
# this is +nil+. +uri+ is the URI of the remote object that this
# will be a stub for.
def initialize(obj, uri=nil)
@uri = nil
@ref = nil
case obj
when Object
is_nil = obj.nil?
when BasicObject
is_nil = false
end
if is_nil
return if uri.nil?
@uri, option = DRbProtocol.uri_option(uri, DRb.config)
@ref = DRbURIOption.new(option) unless option.nil?
else
@uri = uri ? uri : (DRb.uri rescue nil)
@ref = obj ? DRb.to_id(obj) : nil
end
end
# Get the URI of the remote object.
def __drburi
@uri
end
# Get the reference of the object, if local.
def __drbref
@ref
end
undef :to_s
undef :to_a if respond_to?(:to_a)
# Routes respond_to? to the referenced remote object.
def respond_to?(msg_id, priv=false)
case msg_id
when :_dump
true
when :marshal_dump
false
else
method_missing(:respond_to?, msg_id, priv)
end
end
# Routes method calls to the referenced remote object.
ruby2_keywords def method_missing(msg_id, *a, &b)
if DRb.here?(@uri)
obj = DRb.to_obj(@ref)
DRb.current_server.check_insecure_method(obj, msg_id)
return obj.__send__(msg_id, *a, &b)
end
succ, result = self.class.with_friend(@uri) do
DRbConn.open(@uri) do |conn|
conn.send_message(self, msg_id, a, b)
end
end
if succ
return result
elsif DRbUnknown === result
raise result
else
bt = self.class.prepare_backtrace(@uri, result)
result.set_backtrace(bt + caller)
raise result
end
end
# Given the +uri+ of another host executes the block provided.
def self.with_friend(uri) # :nodoc:
friend = DRb.fetch_server(uri)
return yield() unless friend
save = Thread.current['DRb']
Thread.current['DRb'] = { 'server' => friend }
return yield
ensure
Thread.current['DRb'] = save if friend
end
# Returns a modified backtrace from +result+ with the +uri+ where each call
# in the backtrace came from.
def self.prepare_backtrace(uri, result) # :nodoc:
prefix = "(#{uri}) "
bt = []
result.backtrace.each do |x|
break if /`__send__'$/ =~ x
if /\A\(druby:\/\// =~ x
bt.push(x)
else
bt.push(prefix + x)
end
end
bt
end
def pretty_print(q) # :nodoc:
q.pp_object(self)
end
def pretty_print_cycle(q) # :nodoc:
q.object_address_group(self) {
q.breakable
q.text '...'
}
end
end
class ThreadObject
include MonitorMixin
def initialize(&blk)
super()
@wait_ev = new_cond
@req_ev = new_cond
@res_ev = new_cond
@status = :wait
@req = nil
@res = nil
@thread = Thread.new(self, &blk)
end
def alive?
@thread.alive?
end
def kill
@thread.kill
@thread.join
end
def method_missing(msg, *arg, &blk)
synchronize do
@wait_ev.wait_until { @status == :wait }
@req = [msg] + arg
@status = :req
@req_ev.broadcast
@res_ev.wait_until { @status == :res }
value = @res
@req = @res = nil
@status = :wait
@wait_ev.broadcast
return value
end
end
def _execute()
synchronize do
@req_ev.wait_until { @status == :req }
@res = yield(@req)
@status = :res
@res_ev.signal
end
end
end
# Class handling the connection between a DRbObject and the
# server the real object lives on.
#
# This class maintains a pool of connections, to reduce the
# overhead of starting and closing down connections for each
# method call.
#
# This class is used internally by DRbObject. The user does
# not normally need to deal with it directly.
class DRbConn
POOL_SIZE = 16 # :nodoc:
def self.make_pool
ThreadObject.new do |queue|
pool = []
while true
queue._execute do |message|
case(message[0])
when :take then
remote_uri = message[1]
conn = nil
new_pool = []
pool.each do |c|
if conn.nil? and c.uri == remote_uri
conn = c if c.alive?
else
new_pool.push c
end
end
pool = new_pool
conn
when :store then
conn = message[1]
pool.unshift(conn)
pool.pop.close while pool.size > POOL_SIZE
conn
else
nil
end
end
end
end
end
@pool_proxy = nil
def self.stop_pool
@pool_proxy&.kill
@pool_proxy = nil
end
def self.open(remote_uri) # :nodoc:
begin
@pool_proxy = make_pool unless @pool_proxy&.alive?
conn = @pool_proxy.take(remote_uri)
conn = self.new(remote_uri) unless conn
succ, result = yield(conn)
return succ, result
ensure
if conn
if succ
@pool_proxy.store(conn)
else
conn.close
end
end
end
end
def initialize(remote_uri) # :nodoc:
@uri = remote_uri
@protocol = DRbProtocol.open(remote_uri, DRb.config)
end
attr_reader :uri # :nodoc:
def send_message(ref, msg_id, arg, block) # :nodoc:
@protocol.send_request(ref, msg_id, arg, block)
@protocol.recv_reply
end
def close # :nodoc:
@protocol.close
@protocol = nil
end
def alive? # :nodoc:
return false unless @protocol
@protocol.alive?
end
end
# Class representing a drb server instance.
#
# A DRbServer must be running in the local process before any incoming
# dRuby calls can be accepted, or any local objects can be passed as
# dRuby references to remote processes, even if those local objects are
# never actually called remotely. You do not need to start a DRbServer
# in the local process if you are only making outgoing dRuby calls
# passing marshalled parameters.
#
# Unless multiple servers are being used, the local DRbServer is normally
# started by calling DRb.start_service.
class DRbServer
@@acl = nil
@@idconv = DRbIdConv.new
@@secondary_server = nil
@@argc_limit = 256
@@load_limit = 0xffffffff
@@verbose = false
# Set the default value for the :argc_limit option.
#
# See #new(). The initial default value is 256.
def self.default_argc_limit(argc)
@@argc_limit = argc
end
# Set the default value for the :load_limit option.
#
# See #new(). The initial default value is 25 MB.
def self.default_load_limit(sz)
@@load_limit = sz
end
# Set the default access control list to +acl+. The default ACL is +nil+.
#
# See also DRb::ACL and #new()
def self.default_acl(acl)
@@acl = acl
end
# Set the default value for the :id_conv option.
#
# See #new(). The initial default value is a DRbIdConv instance.
def self.default_id_conv(idconv)
@@idconv = idconv
end
def self.default_safe_level(level) # :nodoc:
# Remove in Ruby 3.0
end
# Set the default value of the :verbose option.
#
# See #new(). The initial default value is false.
def self.verbose=(on)
@@verbose = on
end
# Get the default value of the :verbose option.
def self.verbose
@@verbose
end
def self.make_config(hash={}) # :nodoc:
default_config = {
:idconv => @@idconv,
:verbose => @@verbose,
:tcp_acl => @@acl,
:load_limit => @@load_limit,
:argc_limit => @@argc_limit,
}
default_config.update(hash)
end
# Create a new DRbServer instance.
#
# +uri+ is the URI to bind to. This is normally of the form
# 'druby://<hostname>:<port>' where <hostname> is a hostname of
# the local machine. If nil, then the system's default hostname
# will be bound to, on a port selected by the system; these value
# can be retrieved from the +uri+ attribute. 'druby:' specifies
# the default dRuby transport protocol: another protocol, such
# as 'drbunix:', can be specified instead.
#
# +front+ is the front object for the server, that is, the object
# to which remote method calls on the server will be passed. If
# nil, then the server will not accept remote method calls.
#
# If +config_or_acl+ is a hash, it is the configuration to
# use for this server. The following options are recognised:
#
# :idconv :: an id-to-object conversion object. This defaults
# to an instance of the class DRb::DRbIdConv.
# :verbose :: if true, all unsuccessful remote calls on objects
# in the server will be logged to $stdout. false
# by default.
# :tcp_acl :: the access control list for this server. See
# the ACL class from the main dRuby distribution.
# :load_limit :: the maximum message size in bytes accepted by
# the server. Defaults to 25 MB (26214400).
# :argc_limit :: the maximum number of arguments to a remote
# method accepted by the server. Defaults to
# 256.
# The default values of these options can be modified on
# a class-wide basis by the class methods #default_argc_limit,
# #default_load_limit, #default_acl, #default_id_conv,
# and #verbose=
#
# If +config_or_acl+ is not a hash, but is not nil, it is
# assumed to be the access control list for this server.
# See the :tcp_acl option for more details.
#
# If no other server is currently set as the primary server,
# this will become the primary server.
#
# The server will immediately start running in its own thread.
def initialize(uri=nil, front=nil, config_or_acl=nil)
if Hash === config_or_acl
config = config_or_acl.dup
else
acl = config_or_acl || @@acl
config = {
:tcp_acl => acl
}
end
@config = self.class.make_config(config)
@protocol = DRbProtocol.open_server(uri, @config)
@uri = @protocol.uri
@exported_uri = [@uri]
@front = front
@idconv = @config[:idconv]
@grp = ThreadGroup.new
@thread = run
DRb.regist_server(self)
end
# The URI of this DRbServer.
attr_reader :uri
# The main thread of this DRbServer.
#
# This is the thread that listens for and accepts connections
# from clients, not that handles each client's request-response
# session.
attr_reader :thread
# The front object of the DRbServer.
#
# This object receives remote method calls made on the server's
# URI alone, with an object id.
attr_reader :front
# The configuration of this DRbServer
attr_reader :config
def safe_level # :nodoc:
# Remove in Ruby 3.0
0
end
# Set whether to operate in verbose mode.
#
# In verbose mode, failed calls are logged to stdout.
def verbose=(v); @config[:verbose]=v; end
# Get whether the server is in verbose mode.
#
# In verbose mode, failed calls are logged to stdout.
def verbose; @config[:verbose]; end
# Is this server alive?
def alive?
@thread.alive?
end
# Is +uri+ the URI for this server?
def here?(uri)
@exported_uri.include?(uri)
end
# Stop this server.
def stop_service
DRb.remove_server(self)
if Thread.current['DRb'] && Thread.current['DRb']['server'] == self
Thread.current['DRb']['stop_service'] = true
else
shutdown
end
end
# Convert a dRuby reference to the local object it refers to.
def to_obj(ref)
return front if ref.nil?
return front[ref.to_s] if DRbURIOption === ref
@idconv.to_obj(ref)
end
# Convert a local object to a dRuby reference.
def to_id(obj)
return nil if obj.__id__ == front.__id__
@idconv.to_id(obj)
end
private
def shutdown
current = Thread.current
if @protocol.respond_to? :shutdown
@protocol.shutdown
else
[@thread, *@grp.list].each { |thread|
thread.kill unless thread == current # xxx: Thread#kill
}
end
@thread.join unless @thread == current
end
##
# Starts the DRb main loop in a new thread.
def run
Thread.start do
begin
while main_loop
end
ensure
@protocol.close if @protocol
end
end
end
# List of insecure methods.
#
# These methods are not callable via dRuby.
INSECURE_METHOD = [
:__send__
]
# Has a method been included in the list of insecure methods?
def insecure_method?(msg_id)
INSECURE_METHOD.include?(msg_id)
end
# Coerce an object to a string, providing our own representation if
# to_s is not defined for the object.
def any_to_s(obj)
"#{obj}:#{obj.class}"
rescue
Kernel.instance_method(:to_s).bind_call(obj)
end
# Check that a method is callable via dRuby.
#
# +obj+ is the object we want to invoke the method on. +msg_id+ is the
# method name, as a Symbol.
#
# If the method is an insecure method (see #insecure_method?) a
# SecurityError is thrown. If the method is private or undefined,
# a NameError is thrown.
def check_insecure_method(obj, msg_id)
return true if Proc === obj && msg_id == :__drb_yield
raise(ArgumentError, "#{any_to_s(msg_id)} is not a symbol") unless Symbol == msg_id.class
raise(SecurityError, "insecure method `#{msg_id}'") if insecure_method?(msg_id)
case obj
when Object
if obj.private_methods.include?(msg_id)
desc = any_to_s(obj)
raise NoMethodError, "private method `#{msg_id}' called for #{desc}"
elsif obj.protected_methods.include?(msg_id)
desc = any_to_s(obj)
raise NoMethodError, "protected method `#{msg_id}' called for #{desc}"
else
true
end
else
if Kernel.instance_method(:private_methods).bind(obj).call.include?(msg_id)
desc = any_to_s(obj)
raise NoMethodError, "private method `#{msg_id}' called for #{desc}"
elsif Kernel.instance_method(:protected_methods).bind(obj).call.include?(msg_id)
desc = any_to_s(obj)
raise NoMethodError, "protected method `#{msg_id}' called for #{desc}"
else
true
end
end
end
public :check_insecure_method
class InvokeMethod # :nodoc:
def initialize(drb_server, client)
@drb_server = drb_server
@client = client
end
def perform
@result = nil
@succ = false
setup_message
if @block
@result = perform_with_block
else
@result = perform_without_block
end
@succ = true
case @result
when Array
if @msg_id == :to_ary
@result = DRbArray.new(@result)
end
end
return @succ, @result
rescue NoMemoryError, SystemExit, SystemStackError, SecurityError
raise
rescue Exception
@result = $!
return @succ, @result
end
private
def init_with_client
obj, msg, argv, block = @client.recv_request
@obj = obj
@msg_id = msg.intern
@argv = argv
@block = block
end
def check_insecure_method
@drb_server.check_insecure_method(@obj, @msg_id)
end
def setup_message
init_with_client
check_insecure_method
end
def perform_without_block
if Proc === @obj && @msg_id == :__drb_yield
if @argv.size == 1
ary = @argv
else
ary = [@argv]
end
ary.collect(&@obj)[0]
else
@obj.__send__(@msg_id, *@argv)
end
end
end
require_relative 'invokemethod'
class InvokeMethod
include InvokeMethod18Mixin
end
def error_print(exception)
exception.backtrace.inject(true) do |first, x|
if first
$stderr.puts "#{x}: #{exception} (#{exception.class})"
else
$stderr.puts "\tfrom #{x}"
end
false
end
end
# The main loop performed by a DRbServer's internal thread.
#
# Accepts a connection from a client, and starts up its own
# thread to handle it. This thread loops, receiving requests
# from the client, invoking them on a local object, and
# returning responses, until the client closes the connection
# or a local method call fails.
def main_loop
client0 = @protocol.accept
return nil if !client0
Thread.start(client0) do |client|
@grp.add Thread.current
Thread.current['DRb'] = { 'client' => client ,
'server' => self }
DRb.mutex.synchronize do
client_uri = client.uri
@exported_uri << client_uri unless @exported_uri.include?(client_uri)
end
loop do
begin
succ = false
invoke_method = InvokeMethod.new(self, client)
succ, result = invoke_method.perform
error_print(result) if !succ && verbose
unless DRbConnError === result && result.message == 'connection closed'
client.send_reply(succ, result)
end
rescue Exception => e
error_print(e) if verbose
ensure
client.close unless succ
if Thread.current['DRb']['stop_service']
shutdown
break
end
break unless succ
end
end
end
end
end
@primary_server = nil
# Start a dRuby server locally.
#
# The new dRuby server will become the primary server, even
# if another server is currently the primary server.
#
# +uri+ is the URI for the server to bind to. If nil,
# the server will bind to random port on the default local host
# name and use the default dRuby protocol.
#
# +front+ is the server's front object. This may be nil.
#
# +config+ is the configuration for the new server. This may
# be nil.
#
# See DRbServer::new.
def start_service(uri=nil, front=nil, config=nil)
@primary_server = DRbServer.new(uri, front, config)
end
module_function :start_service
# The primary local dRuby server.
#
# This is the server created by the #start_service call.
attr_accessor :primary_server
module_function :primary_server=, :primary_server
# Get the 'current' server.
#
# In the context of execution taking place within the main
# thread of a dRuby server (typically, as a result of a remote
# call on the server or one of its objects), the current
# server is that server. Otherwise, the current server is
# the primary server.
#
# If the above rule fails to find a server, a DRbServerNotFound
# error is raised.
def current_server
drb = Thread.current['DRb']
server = (drb && drb['server']) ? drb['server'] : @primary_server
raise DRbServerNotFound unless server
return server
end
module_function :current_server
# Stop the local dRuby server.
#
# This operates on the primary server. If there is no primary
# server currently running, it is a noop.
def stop_service
@primary_server.stop_service if @primary_server
@primary_server = nil
end
module_function :stop_service
# Get the URI defining the local dRuby space.
#
# This is the URI of the current server. See #current_server.
def uri
drb = Thread.current['DRb']
client = (drb && drb['client'])
if client
uri = client.uri
return uri if uri
end
current_server.uri
end
module_function :uri
# Is +uri+ the URI for the current local server?
def here?(uri)
current_server.here?(uri) rescue false
# (current_server.uri rescue nil) == uri
end
module_function :here?
# Get the configuration of the current server.
#
# If there is no current server, this returns the default configuration.
# See #current_server and DRbServer::make_config.
def config
current_server.config
rescue
DRbServer.make_config
end
module_function :config
# Get the front object of the current server.
#
# This raises a DRbServerNotFound error if there is no current server.
# See #current_server.
def front
current_server.front
end
module_function :front
# Convert a reference into an object using the current server.
#
# This raises a DRbServerNotFound error if there is no current server.
# See #current_server.
def to_obj(ref)
current_server.to_obj(ref)
end
# Get a reference id for an object using the current server.
#
# This raises a DRbServerNotFound error if there is no current server.
# See #current_server.
def to_id(obj)
current_server.to_id(obj)
end
module_function :to_id
module_function :to_obj
# Get the thread of the primary server.
#
# This returns nil if there is no primary server. See #primary_server.
def thread
@primary_server ? @primary_server.thread : nil
end
module_function :thread
# Set the default id conversion object.
#
# This is expected to be an instance such as DRb::DRbIdConv that responds to
# #to_id and #to_obj that can convert objects to and from DRb references.
#
# See DRbServer#default_id_conv.
def install_id_conv(idconv)
DRbServer.default_id_conv(idconv)
end
module_function :install_id_conv
# Set the default ACL to +acl+.
#
# See DRb::DRbServer.default_acl.
def install_acl(acl)
DRbServer.default_acl(acl)
end
module_function :install_acl
@mutex = Thread::Mutex.new
def mutex # :nodoc:
@mutex
end
module_function :mutex
@server = {}
# Registers +server+ with DRb.
#
# This is called when a new DRb::DRbServer is created.
#
# If there is no primary server then +server+ becomes the primary server.
#
# Example:
#
# require 'drb'
#
# s = DRb::DRbServer.new # automatically calls regist_server
# DRb.fetch_server s.uri #=> #<DRb::DRbServer:0x...>
def regist_server(server)
@server[server.uri] = server
mutex.synchronize do
@primary_server = server unless @primary_server
end
end
module_function :regist_server
# Removes +server+ from the list of registered servers.
def remove_server(server)
@server.delete(server.uri)
mutex.synchronize do
if @primary_server == server
@primary_server = nil
end
end
end
module_function :remove_server
# Retrieves the server with the given +uri+.
#
# See also regist_server and remove_server.
def fetch_server(uri)
@server[uri]
end
module_function :fetch_server
end
# :stopdoc:
DRbObject = DRb::DRbObject
DRbUndumped = DRb::DRbUndumped
DRbIdConv = DRb::DRbIdConv
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