Responsive Email design with Rails

It is almost imperative in the recent times, the emails we send out are expected to be responsive with a heavy number of users preferring to read or more like skim through emails from their smartphones. To find the ideal sweet spot that aids in not only developing fully responsive emails, but also to do it quickly and easily is vital. There are lot of factors should be taken into account both from a business perspective and from a developer standpoint. I am listing them here (in no particular order)

1. Responsive design - works consistent across all the devices from mobile layout to the most stringent Outlook Email client.
2. The UI should be consistent with ways to freeze the Headers, Footers and should follow a proper template similar to Rails Action View Layouts.
3. Should be able to easily testable in developer mode with support for Plain text view besides supporting HTML View.
4. Avoiding hardcoding of styles in each and every HTML tag. Hardcoding styles in the email has been the norm in Rails community and other web frameworks as well for a very long time.
5. Should be easily testable in all types of browsers. Even a minor modification/tweak should be tested quickly instead of painfully sending emails again and again.

The following may seem a shorter list, but believe me - to quench all the above criterions I had to go through a lot of different phases with varied learning curves. To attack all the above problems - I would suggest the following tools and libraries to make our lives super simple.

1. Zurb's "Foundation for emails" (previously called Ink) that provides with ready-made available templates to kick start and later customise on top of it to our heart's content.
2. Premailer-Rails - A wonderful Rails pre-processor that makes the email design entirely stylesheet driven as opposed to hardcoding styles directly in the tag. Not only does it removes the pain of having hardcoded styles, it also provides a packages view to render the Plain text automagically - with 0 amount of code required from the developer.
3. Letter Opener - A classical tool by Ryan to quickly preview the emails in development mode.
4. Litmus - If you are into Responsvie email design, you have no reason not to subscribe to Litmus as they provide a comprehensive way to template, design and test your email in in-numerous email clients.

That is it! Combine these tools and with a slight learning curve, you can claim yourself as a fully responsive e-mail designer.

Cheers!

Braga

Streaming vs Synchronus Replication in Postgres

I recently faced one strange issue in Rails which usually questioned some of the basic Relation Database principles. It gave me almost a sleepless night until I was able to get to the Root cause of the issue.

The problem

The problem was pretty straightforward. A Rake task generates an email and the email had two places where the count of documents was mentioned. Ideally they are supposed to be the same - but for some reason it was different.

The pain point

The reason this particular problem was painful because this has not occurred for few years and that it occurred only intermittently. The problem with intermittency is that there is always some theory behind. Here too there was something. Here are steps I had to perform to find the Root cause.

The approach

I first looked into the Rake task's log file which is outputted when my specific Email job runs. Things looked fine there - meaning it completed in under 90 seconds as expected.
The next step was to look at the production logs. The logs as expected was having 30 insert statements - Check. And it also has a read statement for the insert statements before and it was a typical count(*) query. The problem occurred at this point. The count(*) should have returned 30 but instead it returned 4. There comes another count(*) somewhere below in the code - but that returned 30 as expected!

The above step revealed that this problem is not with the Rails layer but something to do with our production database setup. So routed my energy towards there.
The production database environment is a Master-Slave configuration with Master taking Writes and Reads and Slave purely configured to take Reads. Both these nodes are load balanced via a PG Pool server. My initial gut said to investigate some time in the PGPool but that is not much useful as all PG Pool going to do is route traffic.
So I went and read about the Master - Slave Replication configuration. I read about two types of replication. One being synchronous replication and the other being Streaming Replication. Digging into that I found my root cause!

Synchronous vs Streaming Replication

Assume you have two databases A and B with A being a R/W Master and B being R-only Slave. If an insert or update command is issued, it goes and writes that entry to A as its configured for write. If the database returns after it ensures that all the slaves got this write - it is called as Synchronus or 2-Safe Replication. If A does not wait for this step however acknowledge whether it wrote successfully and later streams that value to B - this is called as Streaming Replication.

Both has their obvious own pros and cons. Streaming Replication is for Raw Speed and is also a very good configuration where there are too many writes. And Synchronous Replication although not as fast as Streaming provides 100% consistency. We unfortunately were in Streaming Replication mode. The 30 inserts happened so fast at A, that before even it could stream them to B, the count query intervened and read the half baked data from B. I am talking in terms of millisecond speed.

How did we fix it?

We isolated all our cron jobs to run in a dedicated node and pointed the database directly to the Master database server skipping the PG Pool in the process. In a single database configuration the concept of Streaming or Synchronous Replication does not apply. Hope this was helpful!

Cheers!
Braga

Quick way to import a jar in Eclipse

Following is a quick demonstration to import .jar files via Eclipse IDE

See Also: TRIE ADT Tutorial

You will need to understand why you are doing this. Any java program, for it to execute, first needs to be compiled without errors. The compilation process (using "javac") is going to convert your source code into bytecode (.class) file which you can then use the "java" executable to run. An IDE like Eclipse will do the compilation automatically in the background. That is why when you have any sort of error in the program (syntax/logical etc.,), you see it getting highlighted immediately. 

So, when you are referencing an external library, javac executable needs to know which library you are referencing. You can do this by setting the CLASSPATH variable before executing the program if it is via command line. Eclipse makes it easier, instead of specifying the Java library file's location through the command line, you can do it through the editor by Right clicking on the project and selecting Build Path --> Configure Build Path. With the Libraries tab selected, click on "Add External Archives" and give your .jar files. Your program should now compile smoothly without errors.

Using an IDE introduces insane efficiency for designing and development. However, always have an understanding of what is going behind the scenes. Hope you learned something useful today!

Cheers!

Braga

Hotel Automation Controller - Interview coding problem

This is one of the problems I got via a friend who recently faced a company called Sahaj Software a clone company to Thoughtworks.

Problem Statement:

Hotel Automation Controller Problem  Statement

A very prestigious chain of Hotels is facing a problem managing their electronic equipments. Their equipments, like lights, ACs, etc are currently controlled manually, by the hotel staff, using switches. They want to optimise the usage of Power and also ensure that there is no inconvenience caused to the guests and staff.

So the Hotel Management has installed sensors, like Motion Sensors, etc at appropriate places and have approached you to program a Controller which takes inputs from these sensors and controls the various equipments.

The way the hotel equipments are organised and the requirements for the Controller is below:

• A Hotel can have multiple floors
• Each floor can have multiple main corridors and sub corridors
• Both main corridor and sub corridor have one light each
• Both main and sub corridor lights consume 5 units of power when ON
• Both main and sub corridor have independently controllable ACs
• Both main and sub corridor ACs consume 10 units of power when ON
• All the lights in all the main corridors need to be switched ON between 6PM to 6AM, which is the Night time slot
• When a motion is detected in one of the sub corridors the corresponding lights need to be switched ON between 6PM to 6AM (Night time slot)
• When there is no motion for more than a minute the sub corridor lights should be switched OFF
• The total power consumption of all the ACs and lights combined should not exceed (Number of Main corridors * 15) + (Number of sub corridors * 10) units of per floor. Sub corridor AC could be switched OFF to ensure that the power consumption is not more than the specified maximum value
• When the power consumption goes below the specified maximum value the ACs that were switched OFF previously must be switched ON

Motion in sub corridors is input to the controller. Controller need to keep track and optimise the power consumption.

Write a program that takes input values for Floors, Main corridors, Sub corridors and takes different external inputs for motion in sub corridors and for each input prints out the state of all the lights and ACs in the hotel. For simplicity, assume that the controller is operating at the night time. Sample input and output below.

Initial input to the controller: Number of floors: 2

Main corridors per floor: 1

Sub corridors per floor: 2

Since the hotel management is trying this for the first time, they would be changing the requirements around which electronic equipments are controlled and the criteria based on which they are controlled, so the solution design should be flexible enough to absorb these requirement changes without significant change to the system.

The solution to this problem involves approaching in an object oriented manner. Also we need to see here that we should use a Command/Strategy Pattern given there could be changes in the behavior based on external factors. I have not included the timings from the problem but from on here it should be easily extensible.

Code below:

Cheers!
Braga

Cloning remote PG database and loading in Local environment

For projects involving small to medium sized databases one may require to copy the remote (or production) database onto local environment. I was earlier doing this for my production application using custom pg_dump and then restoring with pg_restore. It was relatively straightforward but still consumed good amount of time. I wanted to automate this using capistrano and this is how I did it

You should note that this is extremely fast because it executes the command on the VPS - usually EC2 which has amazing internet speeds. And then copies it over scp as a single file. You can also add a compression step using the --format option in the pg_dump.

Hope this was helpful!

Cheers!
Braga

Stand still - and you are going backwards!

Imagine you are standing on a moving escalator that is supposed to take you from a Ground level to the Top level - only that its moving in the opposite direction. If you stand still on such an escalator you will hit the bottom soon. In order to not hit the bottom - you need to "at least" walk at the -ve speed of the elevator. For an observer it would still be standing still but thats the least one could do especially being in the software industry.

My blog once had crossed a million page views and the most active time I was during 2010. I think looking back - that was the time I had cracked any problems thrown at me. And I enjoyed it. I still could crack em only that I realise recently I've become rusty. However, I developed a variety of different skills down the road.

Alright I think I am diverging too much from what I wanted to say. In the IT world, one needs to constantly keep learning, keep pushing the limits, get hands dirty on a variety of technologies. If you are a manual tester - try poking at Automation testing. If you are an Automation Engineer - learn about performance/scalability testing. If you are an application developer - explore system development. If you are a software architect - see what is going on in that particular space and try to remain on top. That is the only way you could make sure that you are always on the 99th percentile in this industry.

One has to realise doing the mundane and similar work won't scale as we have already headed and running in the First order differentiation of time (speed). Second order differentiation (acceleration) will make us even more redundant. Can't imagine what we differentiated even one more step. The only way to sustain such challenging epochs is to learn. Learn learn learn!

Cheers!
Braga

Printing the permutation of characters from a classical mobile phone

One of the problems I recently faced.

Input: A set of numbers from a mobile keypad
Output: Print all the combinations of characters for that given number.

For example if the input is 26. Then possible outputs are am, an, ao, bm, bn, bo, cm, cn, co

Solution:

There are many ways to solve this problem. One is using a tree. Another way is to simply do it with recursion. I solved this using a linear approach. If you convert the problem from the text domain to number domain - it will seem very simple.

For example - if the input is something like ['abc', 'def', 'pqrs'] (transformed from digits 237). Then the output would have a simple rule - the first character should come from the first element, second from the second and so on. Writing in an incremental number form for the indexes, you would get:

0 0 0
0 0 1
0 0 2
0 0 3
0 1 0
0 1 1
0 1 2
....
2 2 3

That's it - problem solved. Programatically expressed it here

VIM Cheatsheet

A one page printable cheat sheet for VIM in PDF Format. Direct URL: https://goo.gl/Yu2rpG

Source and credits to RICHARD TORRUELLAS : http://vim.rtorr.com/

Cheers!
Braga

Ransack namespace collision - The search method

I am a big fan of Ransack, the Rails gem for quickly building a quick and easy Search based on pure ActiveRecord queries. For projects that require some on the fly search without having to set up dedicated Search Engines like Elastic Search, SOLR, ThinkinSphinx - this is a very juicy alternative.

However I recently faced one problem when I introduced this to a project where there already was SOLR integrated. It was because of the collision of the search method.

This simply patch did the job for me. All you have to do is include it to your initializers folder say under config/initializers/ransack.rb

That's it, the Ransack library will no longer collide with your existing suite. As a matter of fact the method search deprecated already and the library itself wants us to use the Alias ransack

Cheers!
Braga

Good bye Heroku !

I primarily work on Ruby on Rails and I use to deploy one of my pet projects to Production entirely on the Heroku's free tier. It was a wonderful two years to see having my application running there during which time I had around a thumping 10 Million page views! Heroku's free tier is one of the most used around the world for quickly showcasing development applications. However, my Production application was such that all my needs felt well under Heroku's free tier.

Here are some of the freebies I use to enjoy

• Free Dedicated (techincally not) machine with 512 MB - The reason its technically not because you are allotted a free worker that would go to sleep if the application is not up for 30 minutes. However you could easily overcome this with something like Pingdom.
• Free Postgres Database - Although there was no specific size limit to this other than a maximum number of 5000 rows, I would still say this is one of the best things Heroku offers. Not only your application can talk to it, anything anywhere from the world can talk to the database directly. And that too 100% free!
• Free emails via Sendgrid - A maximum 200 emails per day! Sendgrid's free Addon allows me send upto 200 emails per day. My application's requirement was in the range 20-40.
• Unlimited Job Schedulers - Although they would take one entire and the only worker allotted to you to spin, this is a boon considering you do not have a full fledged linux machine with you. I use to have only one rake task that takes a routine back up of my data as CSV and email it to me.
• Free PG Backup - Again, if you want to routinely backup your data, you don't have to write any complex code. Heroku provides this out of the box and for free!

Now that Heroku is pulling down the curtain on the 24 hour availability or to pay $7 a month, I have no other option to switch to a much better alternative - that is Digital Ocean. Sign up here for a free $10 credit - https://m.do.co/c/21693a3f9c9e

Sad to depart ways, but you made me learn a lot of stuff in these two + years.

Cheers!
Braga

My first ruby gem horoscope is live

I wanted to write a rubygem on my own for a long time. Never had the time really to write one. However, recently I had some spare time during which I wrote this gem called horoscope. This gem will help drafting the horoscope of a person given the birth date, time and the place. Source is hosted at Github. As with every other open source project out there, feel free to fork it and add more to your liking

Screenshot at Github

Proud to release this and I am planning to add more features to this. Also, planning to release different gems. If you want something particular or specific, don't be shy, add it in the comments section and I would be more than happy to contribute!

Cheers!
Bragboy

Tree Traversal in C++

We've already seen many implementations of tree and its uses in java. Lets look at a simple implementation of traversing on a tree in C++. Code has been given below which I think is quite self descriptive.

Regards,
Jack

Write a program to find the number corresponding to a alphabet and vice-versa with the given rule

Problem:
A = 1
B = A*2 + 2
C = B*2 + 3...
1. Write a program to find the number corresponding to a alphabet and vice-versa.
2. Given a series like GREP find the total in numbers. Given a number like 283883, find the shortest alphabetical series corresponding to it.
Compute above recursively when required and do not pre-compute and store beforehand.

Solution:
The solution is straightest-forward. Java code given below.

Cheers!
Braga

Write a program to build a small knowledge base about top "N" movies listed at IMDB

This was an interesting problem that I came across with. This problem is like an open book exam and race against time. The problem had to be solved within an allocated amount of time with a technology stack that is limited only to Ruby/Python/Node.js/Perl.

Few googling here and there and with some knowledge about Ruby I was able to solve this problem within an hour.

Problem Statement:

Build a small knowledge base about top "N" movies listed at http://www.imdb.com/chart/top. Each movie should mention the cast written on the individual page of the movie.
Given the name of a cast member, you should be able to return the movies out of the top "N" movies he/she has acted in. "N" will be passed by the user.
The knowledge base should be built during the runtime and stored in a data structure of your choice.
Q1. For example, if N=3, then you should parse the first 3 movies' individual pages from that page (http://www.imdb.com/chart/top) and build the knowledge base of the cast (there are about 15-20 on every page). Upon querying for "Morgan Freeman", you should return "The Shawshank Redemption". Do not use any external api for this.
Use only Ruby/Python/Node.js/Perl.

Solution:


Cheers!
Braga

Novel finder Program

This was one of the problems that I had faced during one of my interviews. The problem sounded interesting and I was given 1 hour to solve it which I did quite comfortably.

Problem:

The K-doublets of a string of characters are the ordered pairs of characters that are K distance from each other. A string is K-singular if all its K- doublets are different. A string is Novel String if it is K-singular for all possible K distances.

For e.g. take the string FLBL, its 0-doublets are FL, LB and BL. Since all these are different, FLBL is 0-singular. Similarly, its 1-doublets are FB and LL, since they are different FLBL is 1-singular as well. Lastly, the only 2-doublet of FLBL is FL, so FLBL is 2-singular. Hence, FLBL is a Novel String.

Note that the fact that FL is both a 0-doublet and 2-doublet is insignificant as zero and two are different distances.

Input:

The input is one or more non-empty strings of at most 100 capital letters, each string on a line by itself, followed by a line containing only two dollars ($$) signaling the end of the input.

Output:

For each input line, output whether or not it is a Novel string using the exact output format shown below.

Sample Input: (Input File: novel.in)

FLBL

FFLL

ORDINARY

R

QYQRQYY

$$

Sample Output: (Output File: novel.out)

FLBL is a Novel string

FFLL is not a Novel string

ORDINARY is a Novel string

R is a Novel string

QYQRQYY is not a Novel string

Solution:

To attack this problem, you first have to find all the doublets for each distance starting from 0 to the maximum distance which would string's length minus one. Then keep pushing them into a hash set. Whenever the add() method of the Set returns false, it means we are adding a duplicate hence, its not a Novel text. Here is the Java source code.


Cheers!
Braga