Question

我有一个Sinatra应用程序和DRb服务器对象配对。当我尝试将Sinatra params哈希传递给我的服务器对象上的方法时，我得到DRb::DRbConnError … DRb::DRbServerNotFound，但是当我直接传递一个简单的哈希时，同样的方法也可以。

为什么我使用Sinatra params hash得到这个错误？
解决此问题的最简单，最正确的解决方法是什么？

这是一个简单的测试用例：

# server.rb
require 'drb'
class Server; def echo( hash ); hash; end; end
DRb.start_service 'druby://localhost:9007', Server.new
DRb.thread.join

# app.rb
require 'sinatra'
require 'drb'    
SERVER  = DRbObject.new_with_uri 'druby://localhost:9007'
get("/params"){ SERVER.echo(params).inspect        }
get("/hash"  ){ SERVER.echo(hello:'world').inspect }

这两个都在他们自己的进程中运行：

phrogz$ curl http://localhost:4567/hash
{:hello=>"world"}

phrogz$ curl http://localhost:4567/params
DRb::DRbConnError - DRb::DRbServerNotFound:
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1653:in `current_server'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1721:in `to_id'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1050:in `initialize'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:642:in `new'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:642:in `make_proxy'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:559:in `rescue in dump'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:556:in `dump'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:603:in `block in send_request'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:602:in `each'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:602:in `send_request'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:903:in `send_request'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1196:in `send_message'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1088:in `block (2 levels) in method_missing'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1172:in `open'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1087:in `block in method_missing'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1105:in `with_friend'
 /usr/local/lib/ruby/1.9.1/drb/drb.rb:1086:in `method_missing'
 app.rb:4:in `block in <main>'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:1152:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:1152:in `block in compile!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:724:in `instance_eval'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:724:in `route_eval'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:708:in `block (2 levels) in route!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:758:in `block in process_route'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:755:in `catch'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:755:in `process_route'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:707:in `block in route!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:706:in `each'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:706:in `route!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:843:in `dispatch!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:644:in `block in call!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:808:in `instance_eval'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:808:in `block in invoke'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:808:in `catch'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:808:in `invoke'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:644:in `call!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:629:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.2.2/lib/rack/head.rb:9:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.2.2/lib/rack/commonlogger.rb:18:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/showexceptions.rb:21:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.2.2/lib/rack/methodoverride.rb:24:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:1272:in `block in call'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:1303:in `synchronize'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:1272:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.2.2/lib/rack/content_length.rb:13:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.2.2/lib/rack/chunked.rb:15:in `call'
 /usr/local/lib/ruby/gems/1.9.1/gems/thin-1.2.11/lib/thin/connection.rb:84:in `block in pre_process'
 /usr/local/lib/ruby/gems/1.9.1/gems/thin-1.2.11/lib/thin/connection.rb:82:in `catch'
 /usr/local/lib/ruby/gems/1.9.1/gems/thin-1.2.11/lib/thin/connection.rb:82:in `pre_process'
 /usr/local/lib/ruby/gems/1.9.1/gems/thin-1.2.11/lib/thin/connection.rb:57:in `process'
 /usr/local/lib/ruby/gems/1.9.1/gems/thin-1.2.11/lib/thin/connection.rb:42:in `receive_data'
 /usr/local/lib/ruby/gems/1.9.1/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run_machine'
 /usr/local/lib/ruby/gems/1.9.1/gems/eventmachine-0.12.10/lib/eventmachine.rb:256:in `run'
 /usr/local/lib/ruby/gems/1.9.1/gems/thin-1.2.11/lib/thin/backends/base.rb:61:in `start'
 /usr/local/lib/ruby/gems/1.9.1/gems/thin-1.2.11/lib/thin/server.rb:159:in `start'
 /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.2.2/lib/rack/handler/thin.rb:14:in `run'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/base.rb:1234:in `run!'
 /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.2.6/lib/sinatra/main.rb:25:in `block in <module:Sinatra>'

这是在OS X上的Ruby 1.9.2下运行，而不是我觉得它有所作为。

Answer 1

简短回答

您需要添加

DRb.start_service

在尝试拨打远程电话之前，请

到app.rb。

如果您有兴趣

，请说明

使用关联块创建Sinatra params哈希，以处理引用缺失键时的情况（here's the source）。这意味着有一个Proc对象与之关联。

Drb通过编组来回传递参数。但是，来自the Marshal docs：

无法转储某些对象：如果要转储的对象包括绑定，过程或方法对象，类IO实例或单例对象，则会引发TypeError。

因此，尝试通过线路传递此params哈希会有问题，因为它包含一个不可编组的过程对象。

现在进入the Drb docs：

但是，如果无法编组对象，则会传递或返回对其的dRuby引用。这将作为DRbObject实例在远程端出现。在远程代理上调用的所有方法都将转发到本地对象，如DRbObjects的讨论中所述。它的语义类似于普通的Ruby pass-by-reference。

好消息，它应该仍然有效。那有什么不对？在Drb文档中，我们在示例代码中找到了这一点：

# 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.
DRb.start_service

所以看起来正在发生的事情是Drb正在尝试获取过程对象的远程引用以传递给服务器，但由于没有Drb服务设置客户端而无法进行。

原始答案

（我会把它留在这里，这可能是我感兴趣的。这是我的旅程中的一个休息点。这也是一个可能的替代解决方案。有趣的是，它似乎我< / em>现在我提到的知识渊博的人，至少就其原因而言。）

这是一种可行的解决方法。问题似乎是使用块来创建哈希来处理丢失的密钥（Sinatra's params hash is），因此您可以将哈希的内容提取到新的哈希中。 params.clone和params.merge({})似乎都保留了proc（您可以使用Hash#default_proc查看），但是{}.merge(params)（或merge!）会为您提供一个干净的哈希值与Drb合作。

因此，在此示例中，请执行以下操作：

get("/params"){ SERVER.echo({}.merge params).inspect

为什么这种情况发生在Drb和哈希与procs，以及这是最简单或最正确的解决方法，我会留给更有知识的人。

DRb :: DRbServerNotFound通过Sinatra params

1 个答案:

简短回答

如果您有兴趣

原始答案