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The Burlap Sack

A Blog about Butter, Cheese, and Ruby on Rails


RBridge 2.0May 24 2008

RBridge has undergone a lot of bug fixes and I think it’s worthy of a 0.2 release at long last.

1 major enhancement

  • Actually runs headless via the rulang command.

3 minor enhancements

  • Uses optparse for clearer command-line options.
  • Option to specify port, compile directory, mnesia directory, sname, and location of server file.
  • Some error checking, and debug output added. Checks to see if server is already running on specified port.

You can check it out here or just gem install rbridge

Concurrent code in Ruby 1.8.6 through inliningJanuary 7 2008

Slight typo in the code fixed: 2008-01-08

Toshiyuki and I have released a new gem called rbridge which allows us to execute functional, side-effect free, concurrent code directly in Ruby regardless of the version by using Erlang as a processor. This includes using the Mnesia distributed database and ETS/DETS.

To try it out please follow these steps:

1. Download Erlang for your os. Windows has binaries and OS X can be configured with `./configure—prefix=/opt/local` to make MacParts happy. I haven’t yet tried it with Linux but the default configure options should be okay.

2. Download the rbridge gem. `sudo gem install rbridge`

3. Start the rulang server in Erlang on port 9900. Change dir to the gem directory which is usually /usr/local/lib/ruby/gems/1.8/gems/rbridge-0.1/lib and run sudo erlc rulang.erl. Enter the Erlang shell by typing erl. Finally, start the server with rulang:start_server(9900). (There’s a dot at the end of the command).

4. Require rubygems and rbridge in your code and create a new connection to the rulang server. This is the simplest bit of inline code I can think of but there is a lot more we can do: asynchronous access and ruby-style syntax specifically.

require 'rubygems' require 'rbridge' @r = RBridge.new(nil, 'localhost', 9900) puts @r.erl('10*10.')

To read more check out the documentation on ruby-mnesi

rbridge 0.1 ReleasedJanuary 4 2008

FEATURES:

Allows use of Erlang code within Ruby

Changes:

v0.1 / 2008-01-04 (vosechu)

1 major enhancement

  • Allows many-lined Erlang commands when using the Erlang class for direct access.

3 minor enhancements

  • Revised error checking to allow custom resolution
  • stop_server/0 now shuts down any servers running in an erl shell
  • created tests to run with RSpec and autotest (erl server must be running on port 9900).

3 other changes

  • Forked onto rubyforge complete with rdocs, gem, etc.
  • Translated some comments into english as well as the README
  • Packaged explicitly with gpl documentation
Complex commands with RulangJanuary 3 2008

Rulang was giving me a lot of trouble with regards to multi-line commands and complex commands in general. After hacking on it for a while I’ve developed a patch that will allow ruby code such as the following:

require 'rulang' @mnesia = RulangBridge::Erlang.new("localhost", 9900) def find @mnesia.eval(<<-EOF QH = qlc:q([X || X <- mnesia:table(shop)]), F = fun() -> qlc:eval(QH) end, {atomic, Val} = mnesia:transaction(F), Val. EOF ) end puts find

PATCH

diff -u Desktop/rulangbridge/rulang.erl Current Schoolwork/Project/mnesia/rulang_test/rulang.erl --- Desktop/rulangbridge/rulang.erl 2007-05-17 20:25:50.000000000 -0700 +++ Current Schoolwork/Project/mnesia/rulang_test/rulang.erl 2008-01-03 10:12:05.000000000 -0800 @@ -30,11 +30,15 @@ handle_connection(Socket) -> - Reason = (catch communication(Socket)), - gen_tcp:send(Socket, io_lib:format("Error: ~w~n", [Reason])), + try communication(Socket) + catch + error:Reason -> + {gen_tcp:send(Socket, io_lib:format("Error: ~p~n", [Reason]))} + end, ok = gen_tcp:close(Socket). +% Try to evaluate the code submitted throwing an exception if the evaluation +% doesn't work. Return the code submitted. communication(Socket) -> {ok, Binary} = gen_tcp:recv(Socket, 0), {ok, Result} = eval(binary_to_list(Binary)), @@ -43,9 +47,9 @@ eval(Expression) -> - {ok, Scanned, _} = erl_scan:string(Ex
Mnesia to ruby bridge evaluationJanuary 2 2008

Owing to the complexities of building a Rails adapter for Mnesia I’ve been looking into using a Ruby to Erlang bridge and have looked at the various projects that seem to be available and want to share my comments on how each is stacking up so far.

Rebar

Rebar was announced on 2007-04-20 and has since never surfaced to the public as far as his blog and Google are concerned. The code looked to be among the easiest to understand but is thankfully very similar to the Japanese RulangBridge below. The existence of the Japanese project could explain why Tom Werner never finished the project but that’s merely a guess.

Erlectricity

Erlectricity by Scott Fleckenstein was the first project I really tried out and I am impressed by some aspects and disappointed by others. On one hand it was easy to obtain being hosted on RubyForge and Google Code and works well at using Ruby from Erlang. On the other hand it comes with no documentation or rdocs outside of two uncommented examples.

I could never figure out a way to get it to bridge Erlang commands from Ruby but there may be a way that I’m missing; I have to admit I’ve not asked Scott about whether this code c