A Place for my head

Update: Mysql official bindings has been ported to 1.9, look into comments for details
For those who want to stay on the edge, here is modified set of mysql C bindings for Ruby 1.9. Works perfectly well in my small tests.

To compile it:

$ ruby2 extconf.rb
$ make
$ sudo make install

Mysql C bindings for Ruby 1.9

Although its been quite sometime since 1.0 release of BackgrounDRb has been out in the wild, yet a belated post mentioning its features is nonetheless welcome.

Although README document available at, http://backgroundrb.rubyforge.org is quite comprehensive and there is precious little I can add, yet I shall try.

• BackgrounDRb is a Ruby job server and scheduler. Its main intent is to be
  used with Ruby on Rails applications for offloading long-running tasks. However unlike other libraries BackgrounDRb offers tight integration with Rails and hence you can check status of your workers, pass data to workers and get response back, register status of your workers, dynamically start or stop workers from rails and stuff like that.
• BackgrounDRb doesn’t have any DRb in its skin now. Its based on networking library packet, (http://packet.googlecode.com)
• Its stable.
• It has support for thread_pools, storing of results in MemCache clusters
• It comes with its own scheduler and hence you don’t need to muck around with crontab anymore

A Quick overview of installation:

• Get the plugin using:

   piston import http://svn.devjavu.com/backgroundrb/trunk/ backgroundrb

• Remove or backup older backgroundrb scripts/config files in your rails root directory
• Run following command from root directory of your rails app:

   rake backgroundrb:setup

• Have a look at generated config file, RAILS_ROOT/config/backgroundrb.yml and see if there is anything you would like to change.
• Generate a new worker using :

   ./script/generate worker foo

• Read the detail documentation about writing workers and stuff on http://backgroundrb.rubyforge.org
• Start your BackgrounDRb server with:

  ./script/backgroundrb start

• Stop your BackgrounDRb server with:

  ./script/backgroundrb stop

Updates
Getting gtk-ruby installed is a bit tricky, look into the comments for getting it installed. Also, you don’t necessarily need Emacs to use this application.

Another important thing is, it stores your todos and metadata files in a directory called, ~/snippets, so make sure you have that directory. Although newer version of app, automatically checks for the directory. I put up lots of bug fixes, and a tab for viewing completed tasks too, So make sure you are using latest version. Thanks.

Version 1.0.2 of Swat App

Install it with:

sudo gem install swat-1.0.2.gem

Hey there,

Curse me for making this app if you will. But the truth is all the todo applications in GNU/Linux suck, then I thought ok, may be they do not suck enough. So, with some ruby skills at my disposal, I wrote a todo application in Gtk Ruby.

So whats swat?

Swat is a todo list manager for Gnome & Emacs.

Heck : Emacs?

Features:

• Manage your todos, add them according to priority and category.
• Move your todos to wish list, when not feeling like working on them.
• libtomboy bindings for global shortcut(Alt-F11).
• Nice stats for number of tasks finished and added.
• All your todos are in a .org file and hence can be managed from Emacs as well.
• System tray integration.

KeyBindings:

• Alt-F11 : from anywhere, brings the todo window to front.
• Esc : to dismiss todo window.
• Control-N : to add a todo.

Installation :

• sudo gem install swat

Code:

• http://packet.googlecode.com/svn/branches/swat/

Assuming nobody is reading this, I would quietly mention that, I released new version of BackgrounDRb plugin today.
Checkout full announcement here:

http://rubyforge.org/pipermail/backgroundrb-devel/2007-November/001043.html

Here is a sample worker:

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class FooWorker < BackgrounDRb::MetaWorker
  set_worker_name :foo_worker
  attr_accessor :count
 
  def create
    puts "Starting Foo Worker"
    @count = 0
    add_periodic_timer(4) { increment_status}
  end
 
  def process_request p_data
    user_input = p_data[:data]
    result = self.send(user_input[:method],user_input[:data])
    send_response(p_data,result)
  end
 
  def increment_status
    puts "Registering status"
    register_status("stuff #{rand(10)}")
  end
 
  def foobar
    puts "Invoking foobar at #{Time.now}"
  end
 
  def add_values user_input
    p user_input
    return eval(user_input)
  end
end
 
=begin
  problems, with existing things.
=end

If you have any hopes of becoming a Ruby guru, then regular dose of ruby-talk is a must. In this post, I would try to summarize some of the cool stuffs being discussed on ruby-talk.

• In Ruby, having method names that contain “-” can be PITA. So David Black and others were quick to point following approach of doing so:

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  irb(main):002:0> class C irb(main):003:1> define_method("x-y") { puts "Weird method" } irb(main):004:1> end # At which point, the only way to call it is: irb(main):005:0> C.new.send("x-y") # Weird method

  In other words, it’s not worth the trouble and you should find some
  other solution.

• Trans asked on ruby-talk, how can we know, which files are loading or requiring this file. Ara pointed following solution:

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  p Kernel.requiree('main')   require 'b'   p Kernel.requiree('main')   BEGIN { module Kernel h = Hash.new define_method(:requiree) do |of| h[of] end   r = method :require define_method(:require) do |*a| r.call *a h[a.first] = caller end end }

  The interesting bit around, should be noted.

  1	r = method :require

  When you call method and pass method name as a parameter, it returns a closure. Although as pointed by someone it breaks “Rubygems”, and above approach shouldn’t be used. Rather, one should use:

  1	alias_method :old_require, :require

Whoa, how stupid. All you have to do is:

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if((pid = fork()).nil?)
  $0 = "ruby #{worker_klass.worker_name}"

I was reading on twitter experience of scaling rails and use of dtrace. Unfortunately for GNU/Linux users “dtrace” is just a unreality. But if you just concentrate on the results, then you will find that, a major source of bottleneck was use of:

  foo = @someobj.amazing rescue "not_amazing"

Above code is in vogue, because it takes care of a lot of things like:

• if @someobj is nil, then foo defaults to “not_amazing”.
• if @someobj doesn’t support “amazing” method, foo defaults to “not_amazing”.
• And of course the obvious case.

But that code succinctness comes at a cost and you may end up with deep stacktraces. This was a major bottleneck for twitter team.
Above snippet can be written as:

foo = @someobject.blank? ? "not_amazing" : (@someobject.respont_do?(:amazing) ? @someobject.amazing : "amazing")

Not so succinct, but does its job.

Read the details http://blogs.sun.com/ahl/entry/dtrace_for_ruby_at_oscon .

? is Ruby shorthand for referencing a character.

   irb(main):020:0> ?a => 97 
   irb(main):021:0> ?a == "a"[0] => true
   irb(main):014:0> ?? => 63 
   irb(main):015:0> !?? => false 
   irb(main):016:0> !!?? => true

Since ?? equals 63, it is equivalent to true in a boolean test. That means we can negate it with a bang!

We all know how evil class variables are, and they are as dangerous as the “three headed dog” at the dungeon and we shall not talk about it.
But they are necessary for many of the thingies ruby does and used extensively.But today we shall not talk about them.
We saw earlier that, although class instance variables are excellent, but not so friendly to use and they make Ruby look like C++(ahem).

Here goes a little hack, that allows you to define class level attributes based on class instance variables. Since, i often use it in rails and they have taken cattr for class level attributes.

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class Object
  def self.metaclass; class << self; self; end; end
 
  def self.iattr_accessor *args
 
    metaclass.instance_eval do
      attr_accessor *args
      args.each do |attr|
        define_method("set_#{attr}") do |b_value|
          self.send("#{attr}=",b_value)
        end
      end
    end
 
    args.each do |attr|
      class_eval do
        define_method(attr) do
          self.class.send(attr)
        end
        define_method("#{attr}=") do |b_value|
          self.class.send("#{attr}=",b_value)
        end
      end
    end
  end
end

Now you can easily write code like this:

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class Foobar
  iattr_accessor :hello
end
 
Foobar.hello = "I am a class instance atrribute"
p Foobar.hello