And ..... Viren

IRB.start equivalent in Python

2015-10-29T23:45:00.001-07:00

Well, If anytime you wish to use the IRB.start like feature of Ruby in Python.

They way to do it is.

import code
import readline


vars = globals() ## important to carry over the methods and variable define in program to shell
shell = code.InteractiveConsole(vars)
shell.interact()

Some Ruby Thing

2015-07-02T00:34:00.001-07:00

The following post consist of some features in ruby that are lesser known to people.

1. alias for '.call'

class Ticket
  def purchase
    puts "** Purchasing the Ticket **"
  end 
  alias_method :call,:purchase
end

## Following are they way you can invoke the download method
Ticket.new.purchase
## => ** Purchasing the Ticket **
A.new.call
## => ** Purchasing the Ticket **
A.new.()
## => ** Purchasing the Ticket **

2. Disabling (SSL) Certificate Check from all Gems or Ruby Libraries.

unless Rails.env.production?
  class Net::HTTP
    def verify_mode=(verify_mode)
      @verify_mode = OpenSSL::SSL::VERIFY_NONE
    end
  end
end

Note:

Do this only on your local or development environment.
Also the above code only work if the libraries or gem uses 'Net::HTTP' API internally,
Tested with HTTParty,Faraday,RestClient not working with Excon(so Excon adapter over Faraday might not work as well).

3. Locking a file using flock.
Firstly I advise you to read through flock and also this amazing answer by Arjun Shankar.

flock (locking_constant )→ 0 or falseclick to toggle source

Locks or unlocks a file according to locking_constant (a logical or of the values in the table below). Returns false if File::LOCK_NB is specified and the operation would otherwise have blocked. Not available on all platforms.

Locking constants (in class File):

LOCK_EX   | Exclusive lock. Only one process may hold an
          | exclusive lock for a given file at a time.
----------+------------------------------------------------
LOCK_NB   | Don't block when locking. May be combined
          | with other lock options using logical or.
----------+------------------------------------------------
LOCK_SH   | Shared lock. Multiple processes may each hold a
          | shared lock for a given file at the same time.
----------+------------------------------------------------
LOCK_UN   | Unlock.

Example

open(file,'w+') do |file|
  ## lock the file so that no one can use it. 
  file.flock(File::LOCK_EX)
  read(file_name).each do |row|
    file.puts jsonify(row)
  end
end

Thanks.

Use .wgetrc for default wget settings.

2015-04-21T01:00:00.005-07:00

I use wget quite a lot and in the end I always end up using a large number of common options like

-c (to continue/resume a wget process)
--no-check-certificate (ignore ssl certificate check over https)

which eventually make it look very ugly but thanks to .wgetrc I no longer has to do it.

Create a .wgetrc file onto your home directory

JFI, Here how my current .wgetrc look.

continue=on     ## equivalent to -c options
check_certificate=off  ## equivalent to --no-check-certificate

Noting it down here so I just don't forget it future.

Thanks

Using HTTPProxy in Net/HTTP globally.

2015-04-10T02:30:00.000-07:00

There comes a time when you want to Proxy your Net/HTTP request/response in Ruby.

One of the easy ways to do this in NET/HTTP is by passing proxy parameters in '.new' method (during initialization)

proxy_addr = 'your.proxy.host'
proxy_port = 8080

Net::HTTP.new('example.com', nil, proxy_addr, proxy_port).start { |http|
  # always proxy via your.proxy.addr:8080
}

Obviously, this works but then querying the website using GET or GET BY URI method there is no provision to pass any proxy parameters altogether(at least that's what I found out.)

Thankfully Ruby-2.0+ (not available in lower versions though, can be seen over here) has a feature with which you can provide proxy as your ENV variable (http_proxy environment variable) and ruby take care of the rest.

So, upon setting http_proxy in ENV I found, BAAM!!! it worked and it worked globally (i.e it works even on GET and GET BY URL methods mentioned above.)

BTW, I had the following declaration inside my .bash_profile.

export http_proxy= 'http://127.0.0.1:8080' (8080 is the port where my Squid Proxy is functional)

Thanks

Hack With Rack

2015-03-16T07:28:00.001-07:00

Hello everyone, Hope you are having a good day.

Ok, some years ago, one of our clients wanted us to implement Social Network (FB,Twitter,Linkedin) sharing functionality. Knowing all the OAuth implementation that one has to deal with, we decided to use this awesome gem called OmniAuth that does all the heavy lifting tasks of OAuth Authorisation with very basic minimum implementation.

So with OmniAuth we manage to get the work done in time but then we wanted OAuth Authorisation to work with Ajax call as well. I remember going all out crazy (Googling + debugging OmniAuth code) to find a way to do it but honestly we couldn’t find any way do it. (Note: This was some years back I’m not sure about the status as of now.)

So we decide to write our own “Rack Middleware” that tampers with the Omniauth Response and treats the ajax request the way we wanted.

The Middleware

and then we insert the Middleware where we wanted it

Let look at our middleware stack

Yup that's it- a "Hack with Rack" to get a concrete solution for our problem that isn't too fancy but still does the task we needed getting done.

Some Carrierwave Tip n Tricks

2013-09-01T23:45:00.000-07:00

Finally wait is over I mean after nearly a rough patch of virtually no post for an year I back with a post again

As the title suggest it with regards to some tips and tricks that I manage to pull on carrierwave when working on a project

A) Upload Simultaneously to File and S3

I know there are tons of way to do this like upload the file first to server and then using the background process upload it to S3 blah blah .
Even directly upload to S3 is also an options since AMAZON S3 allow CORS

Well all this work great but I kind of not want to do them perhaps, may try some other approach
(Mind you nothing against the other approach mention thus after or already exists)

So what is my approach well basically nothing all you have to do customize your uploader a bit (not heavy customization though )

Consider this is your standard uploader look like with default storage as :file

class MyUploader < CarrierWave::Uploader::Base
  storage :file
  ... blah ...
  ... blah ... 
  ... blah ... 
end

Now to simultaneously upload it to S3 all you have to do is place this in your uploader.

 version :s3_version do
     storage :fog
     def full_file_name
       super.sub(/s3_version_/,'')
     end
   end

So your uploader finally look like this

class MyUploader < CarrierWave::Uploader::Base
   storage :file
    ... blah ...
    ... blah ...

   version :s3_version do
     storage :fog
     def full_file_name
       super.sub(/s3_version_/,'')
     end
   end
end

That it define a version :s3_version (virtually any name you want) and then use storage as :fog in it (make sure to change the REGULAR EXPRESSION incase you chose a different version name other then s3_version)

Note : Also make sure to add the FOG setting for Carrierwave (S3 is just taken as an example it would work it all storage that fog provide)

Now most of you would argue that if say S3 isn't responding/ something goes wrong in S3 over net, then your local storage goes for a toss and I agree completely with that to so I urge viewer to please take a note of this . Well for me I happy taking that risk on my part . :)

B). Delete the record but don't delete the attachment

Well not all would agree with me on this but there are time when we been ask to delete the uploader record but not delete the file stored :)

There could be many reason like in my case there was a requirement that we need to retain the original copy of the client registered agreement even though the client not longer exists

As said there exists even a dozen tons of ways to achieve this as well but let me show you how I manage to pull off this.

All I did is I overwrite the method remove! in my uploader and I also define a attr_accessor against my model (i.e attr_accessor :keep_file on my model)

Enough said time for code

class MyUploader < CarrierWave::Uploader::Base 
  def remove!
     unless model.keep_file
       super
     end
  end
end

Now to secure the storage file and only delete the record all I did is set :keep_file => true and rest is taken care.

What I mean is record are destroyed but not the file from the storage system with this

There is another approach but I now tried and tested it that one would to overwrite the remove?
method something like this (Note I haven't tested this )

class MyUploader < CarrierWave::Uploader::Base 
  def remove?
    false
  end
end

C). Custom the CarrierWave Error Message

Ever since I question/answered my own question I'm seeing that I'm getting a lot of traction on it . What I have asked for is -

How to change the Carrierwave error message and set your own ?.

Well clearly the answer for that is define a key/value in your en.yml for desired carrierwave error message and that it

e.g Let say Carrierwave default message on extensions whilelists valdations is this

You are not allowed to upload %{extension} files, allowed types: %{allowed_types}

Now want is to change reason (reason with held with me :) ) . So all I have to do is this

in my en.yml define something like this

en:
  errors:
    messages:
       extension_white_list_error: 'My Custom Message'

A full list of carrierwave key/value pair can be found over here

That it guys hope you liked the tricks and found it useful

Thank You

Lesson Learnt about MySQL Datatype

2013-08-23T08:00:00.000-07:00

The Content is derived from Rails audiences but it useful for all those guys who ever had used/currently using framework which had/have a sugar coated Database Mapper encapsulated in them now as said it derived from Rails because it too has a ORM mapper called ActiveRecord (All Rails guys would be aware of this) .

The post is to describe how naively we ignore the database ideology and lay all our worries to ActiveRecord and one of this worry is defining Data Type in ActiveRecord .

All Rails guys would be quite familiar with the following command .

rails g migration add_column_to_some_table some_column:float
rake db:migrate

Now this create a datatype FLOAT in database (MySQL) .

Now all look fine up till now but there is problem (if your using MySQL database preferably) .

Problem is , how MySQL intend FLOAT DataType .

According to MySQL documentation . MySQL expect the FLOAT datatype definition to look like this .

alter table some_tables change some_column some_column float (7,4)

I mean float(L,P) .

L => Length of the number 
P => Number of Precision Value

So from above "7" is length of the number and "4" is max precision so the max number that specify (7,4) criteria is 999.9999 .

Now as usual it not mention anywhere in the MySQL documentation what is default format of FLOAT if not specified (because that what the above migration do ,it define a FLOAT without any precision format as expected by MySQL just a common practice I've seen with many developer now) .

So what is the FLOAT format when not specified like above .

The answer is Default Precision (6,0) .

So here how the number format look like with MySQL .

Real World                    MySQL
511111.1221                   511111
51111.1221                    51111.1
5111.1221                     5111.12
 ... ...                      ... ...
 ... ...                      ... ...

You can do the maths for remain series of number .

BUT

Confusion start when you exceed 6 digit .

Real World                  MySQL
5111111.12121              5111110
51111111.12121             51111100
511111111.12121            511111100

So the point is,Now no matter what only 6 digit will be ever be present from LHS(Left Hand Side) btw rest all will be rounded according to the rounding logic .

So Friend a a word of Caution is required before using FLOAT without digit and precision format declaration .

A Lesson well Learnt .

Thanks

What I missing in Rails 2.3+

2012-04-23T11:13:00.002-07:00

Well 3.1 and 3.2 is been out for quite a while now so I intend to dedicate this post is for all those fellow coder who still believe or want to maintain there code with rails 2.3+ to let them know that what actually they are missing

If I happen I go about and write the all new feature of rails 3.1 or rails 3.2 then I guess I will run out of word but still I ensure that I cover most important one though

1. Unobtrusive Javascript :
Before I move ahead and announcement ,Rails 3+ has default javascript framework as jQuery instead of Prototype as opposed to rails 2.3+ and older version (+1 on this) and by adapting HTML standard Rails 3+ encourage developer to write unobtrusive javascript and give them the ability to work seemless of javascript frameworks in our case its jquery(default) so all you need is to install the gem jquery_ujs( you dont have to do this for rails-3.2).If your a prototype support dont get dishearten there is a piece of cake for you too just install the prototype-rails gem and your ready to go

Now all by developer folks would agree with me saying that back in rails 2.3+ days writing erb code server side would turn up looking one big mess in HTML
here what I meant

a simple delete link in rails 2.3+ would look like this

<%= link_to 'Destroy', user, :confirm => 'Are you sure?',:method => :delete %>

under the hood create such a big mess in HTML

<a href="/users/1" onclick="if (confirm('Are you sure?')) { var f = document.createElement('form'); f.style.display = 'none'; this.parentNode.appendChild(f); f.method = 'POST'; f.action = this.href;var m = document.createElement('input'); m.setAttribute('type', 'hidden'); m.setAttribute('name', '_method'); m.setAttribute('value', 'delete'); f.appendChild(m);var s = document.createElement('input'); s.setAttribute('type', 'hidden'); s.setAttribute('name', 'authenticity_token'); s.setAttribute('value', 'FqAHj1L667xA8SmeQjHvVncy8WJz0shaoKjiLHbhQT0='); f.appendChild(s);f.submit(); };return false;">Destroy</a>

same is true if your writing and ajax related code using using any of Rails 2.3+ ajax helper (e.g link_to_remote,remote_form_for etc)

Now with Rails 3+ you can just clean all this mess let me show you how .
link_to_remote is replace with normal link_to syntax with once extra parameter remote => true providing this help in rails understand to create a link that under hood fire an ajax request (identified by jquery_ujs on click)which is basically achieve by creating a custom data-attribute data-remote => true . same is true with confirm

In Rails 2.3+ a normal link_to_remote would look like this.

<%= link_to_remote 'Edit', :url => edit_user_path(user)  %>

this will produce html on browser like this.

<a href="#" onclick="new Ajax.Request('/users/1/edit', {asynchronous:true, evalScripts:true, parameters:'authenticity_token=' + encodeURIComponent('FqAHj1L667xA8SmeQjHvVncy8WJz0shaoKjiLHbhQT0=')}); return 
false;">Edit</a>

not so clean let see the same in Rails3+ with slightly different syntax.

<%= link_to 'Edit' ,edit_user_path(user) , :remote => true %>

would produce the below underlying HTML code in browser

<a href="/users/3/edit" data-remote="true">Edit</a>

Totally unobtrusive Javascript

So now hence forth the both server side and client side code is much cleaner now hooray !!

2. ActiveRelation (AREL - CHAINING QUERY)
I must admit this the first time I heard this it just blew me the ActiveRelation original created by and written nkallen before rewritten by many especially one person Aaron Patterson citing performance issue thankfully it done now.
(want to know more about ActiveRelation please go through this )

What ActiveRelation basically mean is back in Rails 2.3+ if you want to retrieve record from a database you basically would do use any of this

Model.find(:all,:conditions => {} )

e.g (list all user that are admin right in the application)

User.find(:all,:conditions => {:admin => true} )

Now in Rails 3+ you could achieve this using

Model.where('your conidtion')

e.g

User.where("admin =?",true)

Now the basic difference between the above two query interface apart from syntax is that earlier one (Model.find() ) return you all records against your query
but the latter(Model.where) one return you with a relation object which is cool
because this mean I can just chaining the query to every relation object returned

like

Model.where().order().select()

Now the actual query is fired only when you enumerate over your object or you supply a '.all' syntax to end of Query

like

Model.where().order().select().all

So what Rails 3+ essential does is it kind of lazy load all of records only when you actually need it. Simply Awesome

Here list of method that Rails 3+ ActiveRecord provide

 - where
 - select
 - group
 - order
 - reorder
 - reverse_order
 - limit
 - offset
 - joins
 - includes
 - lock
 - readonly
 - from
 - having

Which such Awesome feature Rails 3+ also has support for old syntax to so as to help migrating Rails 2.3+ application to 3+

Just in inline what used to named_scope in rails-2.3+ is 'scope' in rails 3+ hence worth you like to use named scope something like this

scope :admin , where("admin =?",true)

User.admin

3. Action Dispatcher (New Route API)
Yes with all the this amazing changes there are changes in Rails 3+ routing too.In Rails 3+ the Routing API is much more cleaner and sound a bit more Rubyish here I will list the difference between rails 2.3+ and newest syntax

i.Now the routes is laid all under your app name

something like

RentHouse::Application.routes.draw do
  ... 
  ...
  ...
end

(RentHouse is your app name)

instead of ActionController in Rails 2.3+

ActionController::Routing::Routes.draw do |map|
  ...
  ...
  ...
end

ii.Get rid of block parameter(map). Now you see map is now more an options in rails3+

iii. nested resources

In rails2.3+

 map.resources :products do |products|
  products.resources :comments
  products.resources :sales, :collection => { :recent => :get }
 end

Same can be achieve using Rails 3+

  resources :products do
    resources :comments
    resources :sales do
      collection do 
        get 'recent'
      end
    end
  end

 resources :products do
   resources :comments
     resources :sales do
       get 'recent' :as => "collection"  
     end
   end
 end

Sound more rubuies right I dont know about you guys I feel Rails 3+ simple act like DSL where you define Domain logic

iv . Regular Routes

Rails 2.3+

map.connect 'product_describe',:controller => "products",:action => "describe"

In Rails 3+

match 'product_describe', :to => "products#describe"

Look a bit cleaner right

v. Named Routes

In Rails 2.3+

map.describe 'product_describe',:controller =>"products",:action =>"describe"

In Rails 3+

match 'product_describe', :to => "products#describe", :as => :describe

Now there quite a lot more changes in Routes I recommend refer Rails 3+ routing API for more information

vi. Here an announcement coming
"Rails has never been so Rack friendly as Rails3+ is"

Now you can just plug and play any of your rack app in Rails3+ and it way to easy and Routes too is no exception (as rails3+ routes embrace so beautifully just like that whole rails)

mount your rack app all you need is point it in your routes

 match '/rack_it_up',:to => RackItUp

(RackItUp is rack app (sinatra,cramp,or anything else)

So Awesome <3 Rails3+

4. ActionMailer API Rewritten.

This is brand( I mean rewritten) new by Mike Lindsaar I guess we all knew that in Rails 2.3+ ActionMailer use tmail gem well I guess in Rails 3+ it been rewritten with mail gem

Apart from mail gem ActionMailer has separate directory now for all your mailer code. Which I guess I was missing in Rails 2.3+ where one just would write there mailer code inside model. the syntax too is bit change now here a user_creation_mail

Now in Rails 2.3+ you would have code written like this

class DeliveryMailer
  def user_creation_email(user_created,password)
    subject   "User Registration Mail"
    recipients user_create.email
    from 'myapp@test.com'
    body :user => user,:password => password
  end
end

To sent the mail we would call

DeliveryMailer.deliver_user_creation_email(user,"SECRET")

Same in Rails 3+ with mail gem would be written as

class DeliveryMailer
  def user_creation_email(user_created,password)
    @user     = user_created
    @password = password
    @from     = 'myapp@test.com'
    mail(:to => user_created.email,:subject => "User Registration") 
  end
end

Now to deliver this mail all you need to do is call

DeliveryMailer.user_creation_email(user,"SECRET").deliver

Kind of look neat isn't it

Note that we are passing object in instance variables so that we can use them in the email template.

5. ActiveModel

Shout loud if you feel in rails-2.3+ managing tableless model or using some noSQL with model was so much pain

First you need to uncomment -active_record from your environments file asking it(rails) not to be loaded AciveRecord in Rails(really), as if that was not enough.you happen to stumble upon all the errors that you never encounter

(if you want to achieve this in Rails2.3+ here a link.)

Now if you want to associate callbacks or validations with your model. You probably think of writing your own(and there goes DRY ideology) , wasn't there something that has all the underlying ActiveRecord API where all the validation and callbacks would be defined which would help in better managing of noSQL or tableless model easy

Now a step ahead .You think Rails 3+ has it.

ActiveModel is the place where all the validation and callbacks of ActiveRecord are define now we could integrate ActiveModel in your models and you could have all validation and callbacks in a snap.

Great work Guys Love you Rails3+ for this.

6. Faster Development ActiveReload
I guess this was integrated in Rails 3.2 . How activereload gem created by Robert Pankowecki which basically started as project to speed up development environment quickly became the most downloadable library to speed up your development environment insanely fast close 300% faster . Now the good new is that active_reload in merge in Rails 3.2 here the story you may want read .Written by Robert about how his gem active_reload

As his word "Die ActiveReload long live Rails "

All Hail Rails

7. Asset Pipeline
I guess this feature was introduce in Rails 3.1 what it basically means a better management of your assets (images,stylesheets,javascript) for your applications.

As of Rails 3.1 provide you a bunch of assets directory under 'app' ,'lib', 'public', 'vendor' Now you would place any of your assets any where in the assets directory listed under ('app','lib' .. ) and it would be loaded in application .

Also Rails 3.1 has a support for coffeescript and sass default you could write your javascript or stylesheet in coffee or sass and rails would compile the same for you on run time.
(Note that you don't want to do this production as you don't need you asset to compile on every request)
You could also precompile your assets but I recommend you to do this only on production using rake asset:precompile:all

What basically precompile do is consider that you have a application.js

//= require 'jquery'
//= require 'jquery_ujs'
//= require 'basic'

precompile would basically club all the three file 'jquery,jquery_ujs,basic' and compress to a single with md5 hash of content in filename application[md5hash].js something like this

application-908e25f4bf641868d8683022a5b62f54.css

It also create a gzip version of your assets in case if you need to allow web server to render gzip version of your asset to improve transmission

Now back in rails 2.3+ to cache your asset you would do something like this.

<%= javascript_include_tag :application ,:cache => true %>

And rails would create a script tag

<script src=”/javascript/application.js?1335015587” type=”text/javascript” >

(where 1335015587is the last modified time.)

Now I have read and face many time that the web server dont treat the latter one so gracefully (webserverdoesnot treat '?' so gracefully )

great step taken by rails 3 team in fixing this .

Asset pipeline has also support for preprocessor

which mean you could chain your application.cssor application.jswith application.css.sass.erbor application.js.coffee.erb

and can write sass or coffee and erb code in cssor jsand Rails would do all the necessary compiling.

Now this is basically done using Sprocketsas it drill down for each set of processors and compile the file with respect to processor (.erb,.coffee)

8. Template Inheritance
This one I badly needed it I remember how many time I wanted more level of layouting thankful to Rails team we have template inheritance hooked in rails 3+ but I wish rails 2.3 has this although there where gem like rails-template-inheritance to achieve the same.

Here what I meant with Template Inheritance

consider an application where I have login page and internal pages each having different navigation (like About Us,Contact Us, etc) . Now there are several way you can achieve this segregation but using template inheritance you can achieve this by simple define navigation for each controllers in there respective view directory

e.g my application layout preview

 <html>
   <head>
      ..
   </head>
 <body>
   <%=  render 'top-navigation' %>
   <%= yield %>
 </body>
</html>

Now we could define top-navigation partials specific to any controller in there respective directory and rails would render it.

e.g
For UserController Rails will first look for top-navigation partial in the current controller view directory(app/views/usersover here) if it can find one it will look for the partial in the application directory defined in view.

hence the name template inheritance as just like controllers where all controller inherit from application_controller all view inherit from application

9. Erubius support
To be fair I was expecting this I knew sooner or later Rails team will have default erubius support. there are benchmark laid on erubius website that show how fast
erubius is which regard to erb check here Now basically with hardly any noticeable syntactical change you get faster template compiling.If you want to read the path of integration for erubius in rails3+ I must recommend you read thisby Yehuda Katz

Thanks to Rails team

10. Dependency Management
Dependency management was and is major headache in rails2.3+ application unless you are using your application with bundler I still remember getting error like

can load activesupport 2.3.5 already activated activesupport 2.3.11 or some other sort now which bundler already hooked in rails 3 I guess my life is more peaceful

now with Rails 3+ all need do is 'bundle install' that it bundle will manage all your dependency for you ( bundler gem is crafted by highly advance ruby programming) It basically achieve this a DFS (depth first server)

There other list of command like bundle pack , bundle list , bundle exec etc I advice to follow bundle website for more on bundler .

11. Logging Slow Query
Everyday I used to inspect Rails3+ commit and I used to ask myself what next ,what next. Well we have this amazing framework what next now and I seem to get surprise everytime,this one is no exception reading through rails commit in (Rails3.2) I was made aware that hence forth I can log slow query for my application . Awesome man now I dont need to config my mysql to log one

All you need is new configuration parameter.

config.active_record.auto_explain_threshold_in_seconds

determines what's to be considered a slow query. Setting that to nildisables this feature.

Default are 0.5 in development mode nil in test and production modes

Rails 3.2 supports this feature in SQLite , MYSQL(mysql2 adapter) and PostgresSQL

12 . Simpler Code and Better Documentation

All of this but still simpler code management and better documentation ( I wont believe you) I guess I would have said the same but when I looked at rails 3+ code I was wrong far more simpler and modular code and way better documentation than rails2.3+.

Love Rails3+ Keep growing 3> 3> 3> 3> 3> 3>

Deploying Rails App with Passenger and NGINX

2012-04-21T10:31:00.000-07:00

All the ROR begineer every wonder about how the so called ROR expert set and deploy there application in no time. Feeling sorry don't be because after this post you dont have too.

First of all you may like to pause a minute or so and decide the which server you want to use (nginx , apache) depending on your need.

We would be using the awesome nginx server for out post but dont worry if you have apache in your stack hooking up the same is not much different from nginx.

You can download nginx from here or build the nginx based upon distributor package

For Ubuntu it fairly straight forward

sudo apt-get install nginx

(Note: please check your distribution provider for downloading)

but I recommend you to download the nginx source code as one can customized the nginx while configure it with passenger.

Phusion Passenger - a.k.a. mod_rails or mod_rack -- makes deployment of Ruby web application, such as those built on revolutionary Ruby on Rails web framework

Next we can confidently go ahead and install the phusion-passenger gem using

gem install passenger

Once passenger install

Now it time to go ahead and install configure your nginx to work with passenger just go ahead and ran the below command on your favorite shell

passenger-install-nginx-module

(if you have source code of nginx point it when asked by passenger during the above process)

Now passenger will popup a customized configuration depending upon your environment

Here what passenger displayed me.

Please edit your Nginx me configuration file (probably /opt/nginx/conf/nginx.conf ) ,

  http {
    ...
    passenger_root  /usr/lib/ruby/gems/1.8/gems/passenger-3.0.11;
    passenger_ruby /usr/lib/ruby1.8;
    ...
   }
   server {
     listen 80;
     server_name www.yourhost.com;
     root /somewhere/public;   # <--- be sure to point to 'public'!
     passenger_enabled on;
   }

Copy the above content in your nginx.config
(dont worry if your unaware where is your nginx.conf file located passenger will come to rescue in that too) as it would be required you to set up your application now replace 'somewhere' from the above with absolute path for your application

Here how the final configuration look like

worker_processes  1;
events {
  worker_connections  1024;
}

http {
  passenger_root /usr/lib/ruby/gems/1.8/gems/passenger-3.0.11;
  passenger_ruby /usr/bin/ruby1.8;
  include       mime.types;
  default_type  application/octet-stream;
  sendfile        on;
  keepalive_timeout  65;
  server {
    listen       80;
    server_name  myapplication.com;
    root /home/root/application/public;
    passenger_use_global_queue on;
    passenger_enabled on;
    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
      root   html;
    }
  } 
}

Set you Database environment and restart the nginx server

/etc/init.d/nginx restart

(you might want to run this as sudo)

Voila, that it congratulation you have successfully deployed your rails application

Go ahead pat yourself in back for this. :) :) :)

Now enter your application url in your favourite browser you should find it working.
If you can't find it or you land up in error page check nginx error.log

(can be found in nginx.log file) or your application log file for more information it could probably
because you would be missing certain gem or you just missed something from the above list

Hope it help you in someway or other.

Thanks You.

process => process in CarrierWave

2012-04-20T21:49:00.000-07:00

Well this one is for all those who ever used CarrierWave for uploading there files(no matter which files). Now how many of us had actually extended Carrierwave to process a file (i.e writing you own processing for the file e.g In term of image reducing or increasing the quality of image)

I happen to stumble upon this as all I want was to process a csv file which is suppose to be stored in Amazon S3(on upload) using CarrierWave .

Now the aim was to extract all the information from the CSV (sound simple right ) . Yes it is but I resist the thought of putting the file in Amazon S3 server(first) and then downloading the file and to my server and then extract the data from the CSV file and dump it into database. I want it to be more real time(since the file are small size file) I want user to know that the data in CSV is proper or not and can or cannot data in the CSV can be dumped into database citing validations.

So I realized back when I used to consider PaperClip as my first options, paperclip used to provide me options for processing the file here the link if you want to do it for paperclip Good Luck.

Yes I knew now I have to achieve something of this sort ,but how

Well looking at the uploader file generated by CarrierWave I found out that there is process method ,ok now what how do you apply it.
Inspecting the CarrierWave source code ( for default resize process ) I found out that all you need is to define a method wrapped inside a module .

Now it got it.

So to define a custom processing all you need is to define method wrapped in module and include that module in CarrierWave and pass your process method as an argument to CarrierWave process method define in uploader file
Here how I achieve this.
Inside CarrierWave Uploader

class AssetUploader < CarrierWave::Uploader::Base
   include CarrierWave::CSVProcessor
   process :process_csv
end

That it that all you need to do to define your own file processing.
Just go ahead an define your process_csv method inside module define in file inside config/initializers Voila mission accomplished.
Here how I did it (my file config/initializers/csv_processor.rb)

module CarrierWave
  module CSVProcessor
    def process_csv
      ....
      ....
      ....
    end
  end
end

Go hack now with CarrierWave.

By the way if you want to explore the thought of providing custom error message for CarrierWave here a link that you might want to look at

Hope that it help you in someway or other

Auto Login from Iphone Home Screen Shortcut using LocalStorage and Rack

2012-04-14T06:23:00.000-07:00

If you ever worked on Mobile Application and if you have been ever asked to design a web auto login for iOS Home Screen Desktop every

time a user click the Home Screen Shortcut then you might want settle down and read this post bcoz this can help you

The first that I came across when implementing the home screen shortcut how to manage the cookie and how to store in browser

(even when browser is closed)

Thank full to HTML5 as it provide a localStorage I quickly got the insight how where to store the cookie

For any one how aren’t aware of HTML5 localStorage. HTML5 localStorage provide API for storing data locally on browser which can be

access any time by your application in near future.

Now with clear insight of where to store the cookie the next task is how to access it and wrap it in request.

That when Rack Hit me

The idea is to mount a rack application on top rails middleware and then play around with Rails request/response cycle . Let me Hook

up the code to then explain you everything bit by bit

CODE = %{
  <script type="text/javascript">
    (function(){
      var RESEND_REQUEST = {{RESEND}};
      function isFullScreen() {
        return navigator.userAgent.match(/WebKit.*Mobile/) && !navigator.userAgent.match(/Safari/);
      }

      if(isFullScreen()) {
        if(!document.cookie.match(/{{REGEX}}/)){
          var storedValues = localStorage.getItem('__cookie__');
          if(storedValues){
            var values = storedValues.split(';');
            for(var i=0; i < values.length; i++)
              document.cookie = values[i];
          }
          document.cookie = '_cookieset_=1';

          if(RESEND_REQUEST){
            window.location.reload();
          }
        }
      }
    })()
  </script>
}

COOKIE = %{
  <script type="text/javascript">
    (function(){
      var COOKIE = "{{COOKIE}}";
      var lastCookie = null;
      setInterval(function(){
        if(lastCookie != ''+COOKIE){
          lastCookie = ''+COOKIE;
          localStorage.setItem('__cookie__', ''+COOKIE);
        }
      },1000);
    })()
  </script>
}  

  def initialize(app)
    @app = app
  end

  def call(env)
    if iphone_web_app?(env)
      if new_session?(env)
        [200,{'Content-Length' => code(true).length.to_s, 'Content-Type' => 'text/html'}, code(true)]
      else
        status, headers, body = @app.call(env)
        request = Rack::Request.new(env)
        response = Rack::Response.new([], status, headers)
        cookie = String.new
        request.cookies.each_pair do |key,value|
              cookie += "#{key}=#{value};"
        end
        body.each do |part|
          part.gsub!(/<\/head>/, "#{set_cookie(cookie)}")
          response.write(part)
        end
        response.finish
      end
    else
      @app.call(env)
    end
  end

  protected

  def code(resend=false)
    regex = "_session_id"
    if Rails.configuration.session_store.name == "ActionDispatch::Session::CookieStore"
      regex = Rails.configuration.session_options[:key]
    end
    CODE.gsub('{{RESEND}}', resend.to_s).gsub('{{REGEX}}',regex.to_s)
  end

  def set_cookie(cookie)
    COOKIE.gsub('{{COOKIE}}',cookie.to_s)
  end

  def new_session?(env)
    request = Rack::Request.new(env)
    if request.cookies['_cookieset_'].nil?
      true
    else
      false
    end
  end

  def iphone_web_app?(env)
    if env['HTTP_USER_AGENT']
      env['HTTP_USER_AGENT'] =~ /WebKit.*Mobile/ && !(env['HTTP_USER_AGENT'] =~ /Safari/)
    end
  end

Now the idea is to trap the request def new_session? which has no cookie associated with it return the code javascript in response body and extract the cookie from localStorage localStorage.getItem(‘__cookie__’);
associate it with document using document.cookie syntax and re-request the page using window.location.reload()

Voila there you have it next time you open your Home screen shortcut you would not be thrown to login screen citing no active session available.

Hooking all of this in one gem called rack_iphone

Note : There are other way you can achieve the same using parameterized URL (where a URL will be identify with the parameter in it) something like GOOGLE does I Guess.

Providing few links which will further help you so that you don’t stumble upon any roadblocks when building the same
LocalStorage Issue

Hope that it help you in some way or other

Thanks

Viren Negi

libmozjs.so: cannot open shared object file + CouchDB

2011-08-31T09:57:00.000-07:00

Well all the couchdb learner ever ran into this error well it seem that you just miss something

(If you have already have installed and compile couchdb with xulrunner skip this step)
First install the xulrunner package for your distribution.

For Ubuntu guys its straight forward command (I guess it would be same for other guys as well)

sudo apt-get install xulrunner-x.y.z-dev

(Note there are other dependencies related to couchdb installation based on your distribution google and find it) Ubuntu follower here a straight forward link to install couchdb in Ubuntu .

Once xulrunner and all the related dependencies installed .

Just type the below command

./configure  --with-js-include=/usr/lib/xulrunner-devel-w.x.y.z/include --with-js-lib=/usr/lib/xulrunner-devel-w.x.y.z/lib

then

sudo make && sudo make install

Oops !!! I missed something (But What ? Compiled and Installation happened successfully :))
Well It seem that we just didn't created the xulrunner.conf which was the reason why the above error was generating let quickly fix the error.

sudo vi /etc/ld.so.conf.d/xulrunner.conf

Now add the following lines to your file.

/usr/lib/xulrunner-w.x.y.z
/usr/lib/xulrunner-devel-w.x.y.z

Once done save the file and run ldconfig.

sudo /sbin/ldconfig

That it now your ready to go and hack couchdb.

Hope that it help you in someway or other

Thanks You