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DRb :: DRbServerNotFound passing parameters to Sinatra

I have a Sinatra application and a DRb server object paired. When I try to pass a Sinatra hash to a paramsmethod on my server, I get DRb::DRbConnError … DRb::DRbServerNotFound, but the same method works when I pass a simple hash directly.

  • Why am I getting this error using the Sinatra parameter hash?
  • What are the easiest and correct workarounds to solve this problem?

Here is a simple test case:

# 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 }

Both of them work in their processes:

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>'

This works under Ruby 1.9.2 on OS X, but I don't think it matters.

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1 answer

Short answer

You need to add

DRb.start_service

before app.rbtrying to make a remote call.

Explanation if you're interested

sinatra params , , ( ). , Proc.

Drb , . docs:

: , , , , IO , TypeError.

, , .

Drb:

, , dRuby . DRbObject. , , , DRbObjects. , Ruby.

, . ? Drb :

# 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

, -, Drb , , Drb, .

( , . , . . , , , , , .)

. , , , ( ), . params.clone params.merge({}) proc ( Hash#default_proc), {}.merge(params) ( merge!) , Drb.

, :

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

Drb procs, , - .

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