Ruby Threading with a simple Producer - Consumer example

A threading example implementation of the producer - consumer paradigm implemented in Ruby

	require 'thread'
	class Mgr
	# This initiates the queue and the threads
	def self.run
	@mutex = Mutex.new
	@cv = ConditionVariable.new
	@working = true
	@clue_bank = 0
	10.times{|i|
	puts "#{i} started from (#{Thread.current.inspect}"
	Wrk.new.init(i)
	}
	end
	# this methos services the threads to propogate a stop signal
	def self.working?
	@working
	end
	# this method is used by the workers to grab a task from the queue
	# if no talk is available the worker is set to sleep untill awakened
	# the next time new items are pushed into the queue
	def self.get_a_clue
	@mutex.synchronize {
	if @clue_bank>1
	@clue_bank -=1
	@clue_bank
	else
	@cv.wait(@mutex)
	false
	end
	}
	end
	#this method emulates adding new tasks to the queue
	# note: it is not thread safe because its just a simple example.
	# if you need this to be thread safe, then wrap it in a mutex.sync
	# just like in the get_a_clue method
	def self.pop(c)
	@clue_bank += c
	@cv.broadcast
	end
	#this method is used to announce all the threds to stop and terminate
	def self.stop
	@working = false
	@cv.broadcast
	end
	end

view raw mgr.rb hosted with ❤ by GitHub

	require 'open-uri'
	class Wrk
	#the main loop around for a particular thread
	def run
	while Mgr.working?
	clue = Mgr.get_a_clue
	puts "runner #{@i} got #{clue} (#{Thread.current.inspect})"
	if clue
	puts "runner #{@i} working..."
	open("http://giladmanor.blogspot.co.il/")
	puts "runner #{@i} done."
	end
	end
	end
	# an initialization method for a worker
	# note that the thread is browken off at this point
	def init(i)
	@i = i
	Thread.new {
	self.run
	}
	end
	end

view raw wrk.rb hosted with ❤ by GitHub

Upgrading to JRuby | Neo4J | rvm on Ubuntu

While upgrading the Wikibrains server I encountered a few snags, I had to bypass these issues by following these steps:

Purging the RVM/Ruby installations: (source)

sudo apt-get --purge remove ruby-rvm
sudo rm -rf /usr/share/ruby-rvm /etc/rvmrc /etc/profile.d/rvm.sh

open new terminal and validate environment is clean from old RVM settings (should be no output):

env | grep rvm

if there was output, try to open new terminal, if it does not help then restart your computer.

install RVM:

\curl -L https://get.rvm.io | 
  bash -s stable --ruby --autolibs=enable --auto-dotfiles

Then Run:

source /usr/local/rvm/scripts/rvm

Now proceed to installing rails:

gem install rails --version '= 0.3.8'

gem install bundler




creating the application with neo4j.rb:

rails _3.2.8_ new myapp -m http://andreasronge.github.com/neo4j/rails.rb -O

note: at the time of this post, there is a conflict between Neo4j.rb and rails 4 dependencies.

Manipulating server data in an Angular controller

I was experiencing an annoying problem every time I was trying to access data I would get back from the server in an Angular.JS controller.

 

As it turns out, every time I shorthanded and wrote something in the essence of:

$scope.myData = Service.getMyData();

It returns a proxy object that the angular view was able to handle though model binding,  but the controller can't and accessing fields of the returned object would return as undefined.

So, the solution is as simple as it it stupid (Also see angular reference):

By passing a function to the service that would catch the returning data, and do the magic there, the returning object is the data itself and not a proxy.

the shorthand should be replaced with:
Service.getMyData({}, function(d){

      $scope.myData= d;

});

In my implementation I often broadcast an event of my own after the data has returned so other controllers that are dependent on this data my react accordingly:

Service.getMyData({}, function(d){

      $scope.myData= d; 

      Context.broadcast("theDataIsReady");//shaking the $rootScope tree

}); 

 

...

 

$scope.$on("theDataIsReady",function(){
      // a very clever snippet of code
  }); 

Special thanks to Ravit.

Angular.js JSONP with Rails

A couple of snippets to remind myself on how to JSONP angular and rails. (cross domain Ajaxing)



-

	angular.module('myapp.component', ['ngResource']).factory('MyService', function($resource) {
	return $resource('http://giladmanor.com\\:3000/t/t', {alt: 'json', callback: 'JSON_CALLBACK'},
	{ 'send': { method: 'JSONP'}});
	});

view raw service.js hosted with ❤ by GitHub

	class ApiController < ActionController::Base
	after_filter :callback_wrapper
	def send
	render :json=>{:status=>"ok"}
	end
	private
	def callback_wrapper
	unless params[:callback].nil?
	response.body = "#{params[:callback]}(#{response.body});"
	logger.debug "CALLBACK: \n\n #{response.body.inspect}"
	end
	end
	end

view raw service.rb hosted with ❤ by GitHub

-

App Context for Angular.JS

I'm now deep into converting the Wikibrains client application to the Angular.js Javascript infrastructure.

One of the most basic tools I needed was an application wide context to shift around data and events between controllers.

This is what I came up with:

	angular.module('myApp.context', []).factory('Context', function($rootScope, $location) {
	return {
	'contentTypeFilter': "All",
	'contentScopeFilter': "pub",
	'focusedItemId': -1,
	'profileData':{},
	'broadcast': function(eventName){
	console.log("! Broadcasting: "+ eventName);
	$rootScope.$broadcast( eventName );
	},
	'wrapUp': function(){
	return {id:this.focusedItemId, scope:this.contentScopeFilter, content:this.contentTypeFilter};
	},
	'feed': function(scope){
	scope.contentTypeFilter = this.contentTypeFilter;
	scope.contentScopeFilter = this.contentScopeFilter;
	scope.focusedItemId = this.focusedItemId;
	scope.profileData = this.profileData;
	}
	};
	});

view raw Context.js hosted with ❤ by GitHub

	function MyCtrl($scope,Context) {
	//dump Context onto local $scope:
	Context.feed($scope);
	//Shake the tree when the context is changed
	$scope.userChangedFocusItem = function(selectedItem){
	Context.focusedItemId = selectedItem.id;
	Context.broadcast("UserChangeFocusItem");
	}
	// Catch a change in the context and do something in consequence
	$scope.$on('ChangeContext',function(){
	Context.feed($scope);
	});
	}

view raw myController.js hosted with ❤ by GitHub

Javascript Visualization Toolkits

As part of my search for a nice visualization scheme for my projects, I've stumbled upon to consecutive libraries that are manages by the same team of people (owned by Mike Bostock).

The first one is the Protovis library that is no longer under active development, but does have a very nice feature set.

The same team went on to develop a new visualization library called D3.js available on Github.



A simpler set of visualization tools can be found at the flot JQuery plugin. These are mostly linear charts with limited animation, but very useful for most cases of visualization requirements.











In case something really fancy, 3D with a touch of gravity is required, there is always Mr. doob with an assortment of amazing webGL stuff. My personal favorite being the Ball Pool.