Changing PDF Meta Data in Ruby

According to the home page of pdf-toolkit gem :

pdf-toolkit allows you to access pdf metadata in read-write in a very simple way, through the pdftk commandline tool.

1. Install pdftk version 2.02

$ pdftk -version

pdftk 2.02 a Handy Tool for Manipulating PDF Documents
Copyright (c) 2003-13 Steward and Lee, LLC - Please Visit: www.pdftk.com
This is free software; see the source code for copying conditions. There is
NO warranty, not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

2. gem install pdf-toolkit

3. Read or Write pdf meta data.

require 'pdf/toolkit'

pdf = PDF::Toolkit.open('tmux_p3_0.pdf')
#puts pdf.public_methods(false).sort

puts pdf.author
pdf.author='Daffy Duck'
if pdf.save
  'PDF meta-data saved successfully'
else
  'Failed to save pdf meta-data'
end
# save! to raise exception on failure

puts "after change"
puts "Author"
puts pdf.author
puts 'Title'
puts pdf.title
puts 'Subject'
puts pdf.subject
puts 'Page count'
puts pdf.page_count
puts 'Creator (Publisher)'
puts pdf.creator
puts 'Created At'
puts pdf.created_at
puts 'keywords'
puts pdf.keywords
puts 'producer'
puts pdf.producer
puts 'version'
puts pdf.version
puts 'Updated at'
puts pdf.updated_at

4. Verify the meta-data in Preview -> Tools -> Show Inspector. You will see the author, title, subject, producer, creator, creation date, updated date, number of pages etc.

5. Read the tests in the pdf-toolkit source code to see the available methods.

Fast Typing, IDE shortcuts, Fast Coding

It does not matter how fast you type in the keyboard, know every short-cut in the IDE, never use the mouse or how fast you can code. Remember : It's garbage in, garbage out.

The quality of software depends on:

1. Quality of your thinking.
2. Learning from your mistakes. Did you learn from your own mistakes?
3. Are you making new mistakes or oblivious and making the same old mistakes over and over again?
4. Are you learning from the mistakes of others to minimize making mistakes in the first place?
5. Are you learning to master the best practices?
6. Are you reading books by : Martin Fowler, Alaister Coburn, Eric Evans, Robert Martin etc? Are you applying it to your projects?

wrong number of parameters 2 for in stylesheet_link_tag rails

This error occurs with an ambiguous error message. It does not show the line number of the source where the cause of the problem resides. This happened due to sass-rails dependency on sass gem. Since the sass gem was not declared in the Gemfile, the sass-rails upgraded sass gem to 3.4.4 which broke the application layout. By locking the sass gem to a lower version in the Gemfile:

gem sass, "~ 3.2.1"

The sass-rails picked up this version that works.

The Scientific Method of Troubleshooting

Notes from the presentation by Blithe Rocher.

Set of Techniques for Acquiring Knowledge.
Methodical
Systematic

1. Define the Problem
Expected behavior
Actual behavior
Criteria for success

2. Do Your Research
Know your environment
Read the literature
Discussions
Make it fail

3. Establish a Hypothesis
4. Design the Experiment
Divide and conquer
Limit the variables
Try something weird
Hierarchy of Blame

4. Gather Data
Current status
Read the error message

5. Analyze Your Results
 Problem Solved?
Learn anything?
Understand the Why
Future Experiments
Embrace the Success

6. Keep a Good Lab Notebook
You won't remember
Logs aren't enough
Commit messages
Update the docs
Contribute
Blog it
Share the knowledge

How to play with ActiveModel validators in the rails console

1. bundle open activemodel
2. Open the validator.rb file.
3. You can see the comments that shows you how to mixin the validators. Once you mixin, you can add any validator and define a dummy method for the attribute to play with it in the irb:

class Person
  include ActiveModel::Validations
  SSN_REGEX = /your ssn regex goes here/
  validates_format_of :ssn, with: SSN_REGEX
 
 
  def ssn   
    111-11-1111
  end
end

4. Change the ssn method to invalid ssn to test your regex.
 

How to install Exception Notification gem in Rails 4.1

1. Add the gem to Gemfile:

gem 'exception_notification'



bundle install

2. In config/environments/production.rb:

Whatever::Application.config.middleware.use ExceptionNotification::Rack,
  :email => {
    :email_prefix => "[Whatever] ",
    :sender_address => %{"notifier" },
    :exception_recipients => %w{exceptions@example.com}
  }

3. Configure ActionMailer, in config/environments/production.rb:

I am using Sendgrid SMTP API so:

config.action_mailer.delivery_method = :smtp

If you have sendmail installed on the production server:

config.action_mailer.delivery_method = :sendmail

4. In production.rb:
config.action_mailer.perform_deliveries = true
config.action_mailer.raise_delivery_errors = true

How to install pdftk on Mac OS

You can download the installer from https://www.pdflabs.com/tools/pdftk-server/

After installation, open a new terminal and check installation:

$ pdftk --version

pdftk 2.02 a Handy Tool for Manipulating PDF Documents
Copyright (c) 2003-13 Steward and Lee, LLC - Please Visit: www.pdftk.com
This is free software; see the source code for copying conditions. There is
NO warranty, not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$

How to create .ruby-version and .ruby-gemset in RVM

rvm --create --ruby-version use ruby-2.1.2@r42
Reference: Create .ruby-version and .ruby-gemset

How to install latest version of Rails

gem install rails --version=4.2.0.beta1

How to check if ElasticSearch is running

By default elastic search runs on port 9200.

$ curl http://localhost:9200
{
  "ok" : true,
  "status" : 200,
  "name" : "White Pilgrim",
  "version" : {
    "number" : "0.90.13",
    "build_hash" : "249c9c5e06765c9e929e92b1d235e1ba4dc679fa",
    "build_timestamp" : "2014-03-25T15:27:12Z",
    "build_snapshot" : false,
    "lucene_version" : "4.6"
  },
  "tagline" : "You Know, for Search"
}

1. gem install rest-client

require 'rest-client'
RestClient.get('http://localhost:9200')


$ irb
> require 'rest-client'
 => true
> x = RestClient.get('http://localhost:9200')
 => "{\n  \"ok\" : true,\n  \"status\" : 200,\n  \"name\" : \"White Pilgrim\",\n  \"version\" : {\n    \"number\" : \"0.90.13\",\n    \"build_hash\" : \"249c9c5e06765c9e929e92b1d235e1ba4dc679fa\",\n    \"build_timestamp\" : \"2014-03-25T15:27:12Z\",\n    \"build_snapshot\" : false,\n    \"lucene_version\" : \"4.6\"\n  },\n  \"tagline\" : \"You Know, for Search\"\n}\n"
> x['ok']
 => "ok"
> JSON.parse(x)
 => {"ok"=>true, "status"=>200, "name"=>"White Pilgrim", "version"=>{"number"=>"0.90.13", "build_hash"=>"249c9c5e06765c9e929e92b1d235e1ba4dc679fa", "build_timestamp"=>"2014-03-25T15:27:12Z", "build_snapshot"=>false, "lucene_version"=>"4.6"}, "tagline"=>"You Know, for Search"}

How to configure the secret_key_base in Rails 4.1

1. Define an environment variable in .bashrc or .profile on the server:

export SECRET_KEY_BASE='a long string generated by running rake secret'

2. In secrets.yml file :
secret_key_base=<%= ENV['SECRET_KEY_BASE'] %>

3. MyBlog::Application.config.secret_key_base = Rails.application.secrets.secret_key_base

Remember: After deployment all the old sessions will become invalid.

How to add lib directory to the load path in Rails 4.1

   Uncomment the line :  config.autoload_paths += %W(#{config.root}/lib) in application.rb

Installing Redis on Mac

~ $brew install redis
==> Downloading https://downloads.sf.net/project/machomebrew/Bottles/redis-2.8.9.mavericks.bottle.tar.gz
######################################################################## 100.0%
==> Pouring redis-2.8.9.mavericks.bottle.tar.gz
==> Caveats
To have launchd start redis at login:
    ln -sfv /usr/local/opt/redis/*.plist ~/Library/LaunchAgents
Then to load redis now:
    launchctl load ~/Library/LaunchAgents/homebrew.mxcl.redis.plist
Or, if you don't want/need launchctl, you can just run:
    redis-server /usr/local/etc/redis.conf
==> Summary
 /usr/local/Cellar/redis/2.8.9: 10 files, 1.3M

RubyPlus featured on ReadWriteWeb

Check it out : 15 Places to Find Great Screencasts

RubyPlus is now live! .org domain now will be redirected to .com domain.

Installing a specific version of elastic search

brew search elasticsearch

$ brew install homebrew/versions/elasticsearch090
Cloning into '/usr/local/Library/Taps/homebrew/homebrew-versions'...
remote: Reusing existing pack: 2230, done.
remote: Total 2230 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (2230/2230), 714.24 KiB | 12.00 KiB/s, done.
Resolving deltas: 100% (1260/1260), done.
Checking connectivity... done.
Tapped 149 formulae
==> Downloading https://download.elasticsearch.org/elasticsearch/elasticsearch/elasticsearch-0.90.13.tar.gz
######################################################################## 100.0%
==> Caveats
Data:    /usr/local/var/elasticsearch/elasticsearch_bparanj/
Logs:    /usr/local/var/log/elasticsearch/elasticsearch_bparanj.log
Plugins: /usr/local/var/lib/elasticsearch/plugins/

To have launchd start elasticsearch090 at login:
    ln -sfv /usr/local/opt/elasticsearch090/*.plist ~/Library/LaunchAgents
Then to load elasticsearch090 now:
    launchctl load ~/Library/LaunchAgents/homebrew.mxcl.elasticsearch090.plist
Or, if you don't want/need launchctl, you can just run:
    elasticsearch --config=/usr/local/opt/elasticsearch/config/elasticsearch.yml
==> Summary
🍺  /usr/local/Cellar/elasticsearch090/0.90.13: 31 files, 19M, built in 6.8 minutes

Installing Javascript Runtime

1. Uninstalled manually installed nodejs on Ubuntu 12.04. Since my server is managed by Moonshine. Manual installation is a bad idea.

sudo apt-get remove nodejs 

2. Add :

gem 'execjs'
gem 'therubyracer'
to the Gemfile

3. Bundle and deploy.

Installing ElasticSearch using brew

$ brew install elasticsearch
Error: elasticsearch-0.90.9 already installed
To install this version, first `brew unlink elasticsearch'
$ brew unlink elasticsearch
Unlinking /usr/local/Cellar/elasticsearch/0.90.9... 3 symlinks removed
$ brew install elasticsearch
==> Downloading https://download.elasticsearch.org/elasticsearch/elasticsearch/elasticsearch-1.2.1.tar.gz
######################################################################## 100.0%
==> Caveats
Data:    /usr/local/var/elasticsearch/elasticsearch_bparanj/
Logs:    /usr/local/var/log/elasticsearch/elasticsearch_bparanj.log
Plugins: /usr/local/var/lib/elasticsearch/plugins/

ElasticSearch requires Java 7; you will need to install an appropriate JDK.

To reload elasticsearch after an upgrade:
    launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.elasticsearch.plist
    launchctl load ~/Library/LaunchAgents/homebrew.mxcl.elasticsearch.plist
==> Summary
🍺  /usr/local/Cellar/elasticsearch/1.2.1: 31 files, 21M, built in 5.6 minutes

Missing `secret_key_base` for 'production' environment, set this value in `config/secrets.yml`

1. Specify the secret_key_base by using figaro gem. Search on this blog for how to do that.

Installing Phusion Passenger 4.0.45 using Moonshine in Ubuntu 12.04

1. Login to phusion passenger account.
2. Download the license
3. Move the license file to vendor/plugins/moonshine/lib/moonshine/manifest/rails/templates file. The name of the file is the same as the downloaded file name which is passenger-enterprise-license
4. Add the following to the moonshine.yml file:

:passenger:
  :max_pool_size: 3
  :version: 4.0.45 # This is 2 versions behind because according to the moonshine source code, this is the blessed version.
  :enterprise: true
  :download_token: copy-your-download-token-from-passenger-account-here
  :rolling_restarts: true
   
5. Check in the code to bitbucket and do :
   cap deploy

No such file to load -- shadow puppet (LoadError) moonshine error

Copy the following lines to application.rb file.

    # don't attempt to auto-require the moonshine manifests into the rails env
    config.paths['app/manifests'] = 'app/manifests'
    config.paths['app/manifests'].skip_eager_load!