Configure Delayed Job with Elastic Beanstalk

Recently, I got a chance to work with Elastic Beanstalk and trust me, it is not as friendly as Heroku and it took me a little while to get used to with Beanstalk deployments.

I am using delayed_job in my project and the requirement was very simple, i.e. to automate background jobs. On heroku we simply add a worker dyno and jobs start working immediately. But, same is not the case with Beanstalk. I came across with various article where people suggested to add a shell script inside `.ebextensions` but I did not find this a full proof solution. Then my colleague suggested me to try `active_elastic_job` @ https://github.com/tawan/active-elastic-job

I find this gem extremely helpful and the installation instructions are super simple.

In this article, I will not dig into how to configure, install and start using this gem (because if you visit the link, the steps are defined in simplest form and should not block you). My idea, is to highlight/cover the areas which are not mentioned there or missing.

1. When you create a worker environment, skip selecting the RDS section (which means you’ll create your worker environment without a RDS DB).

2. Now you’ll have to use the existing database (which your web environment is using). For that, copy all RDS environment variables from web environment to your worker environment.

3. Once above is done, deploy your the code to your worker environment. In case your deployment fails with reason:


PG::ConnectionBad: could not connect to server: Connection timed out

Then, go to Services ~> Elastic Beanstalk ~> You Web Application ~> Configuration ~> Instances ~> Modify and note down the Security Group there (using new UI of Beanstalk)

Now, go to Services ~> Elastic Beanstalk ~> Your worker application ~> Configuration ~> Instances ~> Modify and check the security group which your Web Application is using (Note that you can check as many as you want) and Save your changes. This should allow your worker app to use the same DB.

4. Once you have successfully deployed and configured your worker app and you get:


ActiveJob::QueueAdapters::ActiveElasticJobAdapter::SerializedJobTooBig
The job contains bytes in its serialzed form, which exceeds the allowed maximum of 262144 bytes imposed by Amazon SQS

That means you are not allowed to send more than 256KB of data to delayed job. This could prove a bottleneck and you’ll have to think of a workaround to deal with this error. Although, folks on internet suggested that we could use Amazon Extended Client Library for JAVA @ https://github.com/awslabs/amazon-sqs-java-extended-client-lib but I wasn’t able to use and apply this in my Rails app.

Having said that, if anyone knows how to use this in Rails, please drop a comment or as an alternate try to send data < 256KB to SOS queue

That’s all I have for now. See you soon! Happy Coding. 🙂

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[Ruby]: Update hash values with Array

Hi Folks,

In this small tutorial, I am writing a program that updates value of each element in hash with a given array values.
Given that:
h = { h1: 'value1', h2: 'value2', h3: 'value3', h4: 'value4' }
a = [ '1', '2', '3', '4' ]
Where h is a Hash and a is an Array

Output we would like to achieve here is:
h = { h1: 'value1_1', h2: 'value2_2', h3: 'value3_3', h4: 'value4_4' }

Let’s code it:

h = { h1: 'value1', h2: 'value2', h3: 'value3', h4: 'value4' }
a = [ '1', '2', '3', '4' ]

h.each_with_index do |(k, v), i|
break if a.size > h.keys.size

a.each_with_index { |val, index|
if i == index
h[k] = v.to_s + ‘_’ + val.to_s
end
}
end

p h.inspect
# Output => h = { :h1 => “value1_1”, :h2 => “value2_2”, :h3 => “value3_3”, :h4 => “value4_4” }

I’ve tried to minimize the number of loops here. Appreciate your feedback and suggestions.

Happy Coding! 🙂

[Ruby] Fetching Emails from Microsoft Outlook

Hi Folks,

Hope everyone is fine and doing good. In this article of mine, I am going to narrate, how you can fetch Emails from your Microsoft Outlook account. I am only going to cover ‘Inbox‘ here. However, the scope of library (Gem) is very vast and you can customize this as per your need.

PREREQUISITE:

  • Ruby
  • ViewPoint Gem: gem install viewpoint

For Debugging, I am using viewpoint/logging/config

Hope this helps someone! Keep in touch and Happy Coding 🙂

Puneet

Kick-Off: First Rails 4 Application with HABTM Association

Hello Folks,

Its been a long time since I’ve not written a post. Now, I realize that it’s time to share some useful snippet with all of you.

Recently, I got a chance to get my hands cleaned with Rails 4. So much is happening around Rails community and with the rapid development of Rails 4, I was finding it bit difficult to keep my momentum going.

Well, leave all this apart. Now, by putting some extra efforts my system is ready with:

Ruby 2.1 & Rails 4.1

In order to start with my first Rails 4 Application, I took HABTM Association (weird, isn’t it?). It came randomly into my mind. However, I will dig into other associations as well with time, but to start with let’s take HABTM association with example.

I assume most of you are aware what changes Rails 4 has introduced. If you’re new to Rails 4 or would like to re-visit the changes, here’s the most useful link I’ve found. Just take a look.

Once you’re sure about changeset in Rails4, let’s draw an example:

Prerequisites:

  • Ruby 1.9.2+
  • Rails 4.1.0+
  • Traditional Database (MySQL/Postgres)

Key-Entities:

  • Person Model
  • Communtiy Model
  • A Join Table

Defining the Relationships & creating tables:

For rest of the code-flow (controllers, views) you can download the zip of the application from my GitHub page, run it on your local and see Rails4 HABTM in action.

Happy Coding 🙂

Add duplicate rows in Excel using Ruby

Happy New Year Folks,

Few days back a friend of mine came to me and said, “I am a RUBY Programmer and I am stuck in a requirement, wherein I have to read an excel-sheet (that contains multiple records and each record can have multiple entries in it.)”

Think of an example like given in the link: timesheet. It says we have 2 columns: EmployeeID and WorkingHours. Each EmployeeID can have multiple working hours.

Now, I would like to write a small Ruby program that iterate over each record in the excel, combine EmployeeID’s that has multiple entries and add working hours.

Let’s code it then!

Requirements:

  • Ruby 1.9.2 or higher
  • Spreadsheet gem: to read Excel
  • Download timesheet excel from the link above

Happy Coding! 🙂

Ruby Cheat-Sheet

Hi Folks,

In this new tutorial, I am going to show you what most of developers/programmers already know, but not able to keep track of such things. I call it as ‘Ruby cheat-sheet‘, you can call it by the name you like.

This will also help those people who have just started learning ‘Ruby’.

IMPORTANT NOTE:

  • I will keep on updating this article frequently.
  • Also need your valuable response, if you feel there is a better/easy concept available.
  • If I am not sure of something or don’t know the concept, I am going to highlight that with ‘Red‘ color. Later, you can put your opinion in the comment section and I will update that with your name.
  1. Symbols (e.b :name, :age etc.) as just a convenient way of referencing a name.
  2. You don’t need to per-declare a symbol.
  3. A ‘Class‘ is a combination of state (for example, the name of the animal) and method that use that state (perhaps the method how animal eats).
  4. The standard ruby constructor is ‘new‘.
  5. Every object in Ruby has a unique ‘Object identifier‘ (called as Object ID).
  6. Class have instance methods. These instance methods have access to the object’s instance variables.
  7. Methods are defined with the keyword ‘def‘ followed by method name.
  8. The most common way to create String objects in Ruby is ‘string literals‘. (E.g. “I am a string”, ‘I am another string’)
  9. The logical difference between ‘Single quotes‘ and “Double quotes” in Ruby is the amount of processing Ruby does. In double quote case, Ruby first looks for substitution and replaces them with some binary value. (E.g. puts “Good Night, \nAuthor”)
  10. Global variables: starts with ($) sign: E.g. $name
  11. Instance variable: starts with (@) sign: E.g. @name
  12. Class variables: starts with (@@) sign: E.g. @@name
  13. Class name, module name and Constants: Starts with the uppercase letter: E.g class MyClass, module Login
  14. Array stores collection of object with a key to access them.
  15. An array can have objects of different types.
  16. Hash contains key, value pair.
  17. Ruby treats ‘nil’ as false in conditions.
  18. A regular expression is a way of specifying a pattern of characters to be matched in a string.
  19. The match operator (=~) can be used to match a regular expression against a string.
  20. Yield (yield) is a Ruby method
  21. In Ruby, nil is also an Object
  22. When you run Ruby programs you can actually pass arguments. This concept is called command-line-arguments. For e.g. ruby my_example.rb firstname lastname city.
  23. The initialize method in Ruby lets us set the state of each object. When we call ClassName.new to create a new object, Ruby allocates some memory to hold an UN-initialized object.
  24. When we pass an object to puts based on the class, it writes the name of the object’s class, followed by a colon and a unique identifier.
  25. Ruby gives flexibility to its programmers. You can over-write the default methods. (E.g. def to_s)
  26. attr_reader is the modified way of accessor methods.
  27. attr_accessor provides you to read and write methods. (E.g. attr_accessor :age)
  28. Virtual attributes**
  29. require‘, ‘require_relative‘ & ‘load
  30. Access Controls – ‘Public‘, ‘Private‘ & Protected
  31. In ‘Ruby’ a variable is not an Object. It is simply reference to an Object.
  32. initialize‘ is a private method in Ruby.
  33. Block, Procs and Lambda are ways of grouping code we want to run. These are examples of closure in Ruby.
  34. Both Proc and Lambda are Proc Objects.
  35. Lambda check the number of arguments and throws argument error, whereas Proc does not.
  36. In “Inheritance“, if class B inherits the property of class A, then all the methods of class A becomes the member of class B.
    • Assuming child = Child.new; then child.superclass => Parent
    • parent.superclass => Object
    • Object.superclass => BasicObject
    • BasicObject.superclass => nil
  37. Modules: is a way of grouping together Methods, Classes and Constants.
    • Provide namespaces and prevent name clashes.
    • Supports the mix-in functionality.
    • A Module is not a class.
    • A Module cannot have instances.
    • We can always include a module in a class definition – After doing that all module instance methods are suddenly becomes available as methods in the class. They get mix-in.
    • mix-in modules don’t use instance variable directly. They use accessors to retrieve data.
  38. self.method_name: Gives you access to the current object.
  39. begin-rescue blockUse for exception handling.