Software Engineering Blog

Hadoop ecosystem, Scala, Java, Go, Micoroservices

Case Study - Solve Crosswords Puzzle

As a software engineer, I always enjoy solving problems and that’s why I sometimes go to the coding challenge websites like hackerrank and pick one problem to solve. This time I searched in functional programming category and crosswords-101 caught my eye and I decided to solve it in Scala in a very clean and understandable way and not in a contest style way of programming! This article is going to reveal how I solved this puzzle.

Slick Actions Composition

Problem You want to insert a new row to a table which has auto increment primary key; Also some additional information must be persist in other tables. At the end you also want to return the inserted generated ID. Imaging you are developing a new web application, and you are working on user registration code. Each time a new user signs up, you want to store his credential in users table and all of his roles in userRoles table.

More Readable Code in Scala

As a Java developer, I ’ve always had argument with my colleagues to use Scala instead Java. They complained that Scala is a complex language and Java is a more readable and simple one so I never had the opportunity to use Scala well. Fortunately, recently I ’ve just joined to the startup company called snapptrip.com, and we use Scala for all the backend services. A few days ago, I was working on a peace of code in Scala to register a new user into the database.

Writing Internal DSL in Scala

Definition of DSL A DSL is a computer language, specialized for a specific domain. A DSL is essentially the opposite of a general programming languages(GPL), I mean every language that can be used to develop something. For example, Java, C#, and Scala are all GPL languages. With a DSL, we want only to solve a specific domain problem, so we design the language specifically for the domain. A DSL can’t be used outside of the domain, because it is not designed for flexibility.

Dev tools: ngrok

Have you ever wanted to show your work which is running on your local machine to your colleagues or friends? If they are far away of you, how will you show them? Will you upload your source code to github to share it with your friends? But what if you don’t like to share your source code with others? Will you run it on public or private cloud or something like that?

5 ways to customize Spring MVC JSON/XML output

To adhere to guidelines or requirements, API designers may want to control how JSON/XML responses are formatted. Spring Web makes use of Jackson to perform JSON/XML serialization. Therefore, to customize our output format, we must configure the Jackson processor. Spring Web offers XML-based or Java-based approaches to handling configuration. In this article, we will look at the Java-based configuration. Enable XML output First of all, if you have created your project through https://start.

Function Memorization in Go

Memoization is an optimization technique used to increase performance by storing the results of expensive function calls and returning the cached result when the same input occurs again. In this post I show how function memoization can be implemented in Go, in a pure functional manner. Based on wikipedia definition, a function may be considered a pure function if both of the following statements about the function hold: 1. The function always evaluates the same result value given the same argument value(s).

setcap Linux Command

Today I learned something new that I want to share with you. I knew that listening on port below 1024 requires special privilege, and to accomplish that you must be sudoers. But running applications with sudo is not a perfect way because that way the application can do almost anything to your operating system resulting unexpected results (you surely don’t want the application delete all your files by rm -rf).

Enhance Hadoop MapReduce Speed for small jobs

Introduction There are some circumstances when input of Hadoop’s MapReduce is relatively small. Consequently the overhead of allocating and running tasks in new containers outweighs the gain to be had in running them in parallel, compared to running them sequentially on one node. Such a job is said to be uberized, or run as an uber task. Enable uber optimization To enable uberized job, simply set mapreduce.job.ubertask.enable to true. But that is not sufficient.

Kafka Streams + SSE = Realtime web app

Last week I decided to dirty my hands with Kafka Streams. I wanted to write simple application with Kafka Streams more interesting than World Count. I decided to write a program that calculates top 5 using Kafka Streams. Imagine you have written a game, and you want to display top 5 users. You also need that calculating and displaying top 5 to be real time. You need whenever a user has hit a record, it automatically displays user record.