rack-bert-rpc

rack-bert-rpc a Rack middleware BERT-RPC Server implementation. HTTP requests matching the specified path are intercepted by the middleware and interpreted as BERT-RPC requests.

For more information about the BERT-RPC specification go to bert-rpc.org.

rack-bert-rpc varies from other BERT-RPC server implementations in that it requires the requests to be made over HTTP. This increases the complexity and size of the requests, but allows for them to be handled by the same server that is serving a web application. For this reason services exposed through rack-bert-rpc cannot be called using traditional BERT-RPC libraries such as bertrpc

Currently rack-bert-rpc only supports the following BERT-RPC features:

• call requests
• cast requests

The design and implementation of rack-bert-rpc derives heavily from ernie

$ [sudo] gem install rack-bert-rpc

Install rack-bert-rpc as part of your application's middleware stack.

use Rack::BertRpc, :expose => {
  :mod => Mod
}

The BertRpc middle takes several configuration parameters:

• expose Takes a Hash of module name to actual module
• path Any requests coming in to this path will be handled as RPC requests. Defaults to '/rpc'
• logger This is a Logger object that will be used for logging messages from the RPC server. If no logger is provided a default one will be created that logs to STDOUT
• server Used for testing, switches out the backend BertRpc::Server so the requests can be handled by a different one

Modules can also be exposed through class level methods on Rack::BertRpc. For example:

Rack::BertRpc.expose(:mod, Mod)

exposes the module Mod as :mod. This list of exposed modules can be cleared using Rack::BertRpc#clear_exposed. Note: this will only clear modules listed through Rack::BertRpc#expose, not those exposed through the Rack configuration.

First define a module containing the function that you want to call:

module HelloWorld
  def say_hello(name)
    "Hello, #{name}!"
  end
end

Next in your application's config.ru install rack-bert-rpc and expose the HelloWorld module

require 'rack/bert_rpc'
require 'hello_world'

use Rack::BertRpc, :expose => {
  :hello => HelloWorld
}
run lambda{ |env| [200, {}, "success"] }

Since we are calling BERT-RPC over HTTP we can't use the default bertrpc gem. Instead here's a sample script to send a BERT-RPC request over HTTP to test our module

require 'bert'
require 'net/http'

def encode(msg)
  m = BERT.encode(msg)
  [m.length].pack('N') + m
end

def decode(msg)
  io = StringIO.new(body)
  length = io.read(4).unpack('N').first
  BERT.decode(io.read(length))
end

req = Net::HTTP::Post.new('/rpc')
req.body = encode(t[:call, :hello, :say_hello, ["Ryan"]])
resp = nil
Net::HTTP.start('localhost', 3001){ |http| resp = http.request(req) }

puts decode(resp.body)[1]

Next start up your rack server on the appropriate port

$ rackup -p 3001 config.ru

And finally run the script to make the BERT-RPC request

$ ruby -rubygems call_bert.rb
Hello, Ryan!

If you'd like to contribue to rack-bert-rpc fork the project on GitHub:

http://github.com/crystalcommerce/rack-bert-rpc

When your changes are ready, push the code to GitHub and send us a pull request.