Try : Handling exceptions with grace in Scala. [Functional way with Scala]


Hey everyone, it’s time to continue our previous blog on how to make our code more robust, concise and better functionally defined at the same time. Here we are moving more towards Scala and leaving traditional Java behind. We will see new types and their usage along with the benefits we get from them.

This blog will show you the best way in my perspective to be used in order to handle the exceptions gracefully in Scala ( The beloved coding language for everyone here at Knoldus ) . Our methods would only be responsible for either returning the results or the exceptions, i.e. we will not write any try-catch blocks to handle the exceptions within different methods.

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Dribbling about Scala Value Classes, Universal Traits and Extension methods

In this blog , I will share my working knowledge on Value Classes, Universal Traits and Extension methods of Scala.

Let’s start with the Value Classes of Scala. In this section we will talk about Value Classes Introduction, Use Case and it’s limitations.

Value classes have been around in Scala for a long time internally, and we have used them already many times because all Number’s in Scala use this compiler trick to avoid boxing and unboxing numeric values from int to scala.Int etc.

As a quick reminder, let’s recall that Array[Int] is an actual JVM int[] which has tons of performance implications, but in one word — arrays of numbers are fast, arrays of references not as much.

In more specific technical terms Value classes are a new mechanism in Scala to avoid allocating runtime objects. This is accomplished through the definition of new AnyVal subclasses. They were proposed in SIP-15.


Ok, since we now know the compiler has fancy tricks to avoid boxing ints into Ints when it doesn’t have to. Let’s see how this feature is exposed for us, end users since Scala 2.10.x. The feature is called “value classes”, is fairly simple to apply to your existing classes. Using them is as simple as adding extends AnyVal to your class and following a few rules listed bellow.

  • Value Class must have only a primary constructor with exactly one public, val parameter whose type is not a value class. (From Scala 2.11.0, the parameter may be non-public.)
  • Value Class may not have specialized type parameters.
  • Value Class may not have nested or local classes, traits, or objects
  • Value Class may not define a equals or hashCode method.
  • Value Class must be a top-level class or a member of a statically accessible object
  • Value Class can only have defs as members. In particular, it cannot have lazy vals, vars, or vals as members.
  • Value Class cannot be extended by another class.

Now we have enough descriptions about Value classes. Let’s go with a simple example of it. I will be using Case (Value) Classes in all my examples here, but it’s not technically required to do so. We can implement a Value Class using a normal class with one val parameter instead, but using case classes is usually the best way to go.

case class Hour(value: Double) extends AnyVal {
  def toMinute: Minute = Minute(value * 60)

case class Minute(value: Double) extends AnyVal {
  def toHour: Hour = Hour(value / 60)

Now we need to know about two important keywords related to Value Classes which is Universal Traits and Extension methods.

  • A universal trait is a trait that extends Any, only has def s as members, and does no initialization. Universal traits allow basic inheritance of methods for value classes, but they incur the overhead of allocation.
  • Extension methods serve the same purpose as Implicit conversions (which are a more general and more powerful utility), yet are better than conversions in one simple way — they avoid having to allocate the “Wrapper” object, which implicit conversions would otherwise use to provide the “added methods”. Extension methods take the route of rewriting the generated methods a little, so that they take the type-to-be-extended as their 1st argument.

These are the basics around Value Classes, Universal traits and Extension methods. If you want to read more about the different edge-cases around them, please refer to the official documentaion’s section about Value Classes where Mark Harrah, explains them very well with tons of examples, so I won’t be duplicating his effort here beyond the basic introduction 🙂 . As next step, I would look at how I can explain the use case of Value Classes and It’s functionality 🙂 Stay tuned.

Handling HTTPS requests with Akka-HTTPS Server


Hi guys,

In my last blogs I explained how one can create a self-signed certificate and KeyStore in PKCS12. You can go through the previous blog, as we’ll be needing certificate and keystore  for handling HTTPS requests.


Akka-HTTP provides both Server-Side and Client-Side HTTPS support.

In this blog I’ll be covering the Server-Side HTTPS support.

Let’s start with “why do we need server-side HTTPS support?”

If we want the communication between the browser and the server to be encrypted we need to handle HTTPS request.  HTTPS is often used to protect highly confidential online transactions like online banking and online shopping order forms.

Akka-HTTP supports TLS(Transport Layer Security).

For handling the HTTPS request we need to have the SSL certificate and the KeyStore. Once you have generated both you can go through the example.

In this example, you will see how easily you can handle

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Lambda Architecture with Spark


Hello folks,

Knoldus  organized a knolx session on the topic : Lambda Architecture with Spark.

The presentation covers lambda architecture and implementation with spark.In the presentaion we will discuss components of lambda architecure like batch layer,speed layer and serving layer.We will also discuss it’s advantages and benefits with spark.

You can watch the video of presentation :

Here you can check slide :

Thanks !!


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Finding the Impact of a Tweet using Spark GraphX


Social Network Analysis (SNA), a process of investigating social structures using Networks and Graphs, has become a very hot topic nowadays. Using it, we can answer many questions like:

  • How many connections an individual have ?
  • What is the ability of an individual to influence a network?
  • and so on…

Which can be used for conducting marketing research studies, running ad campaigns, and finding out latest trends. So, it becomes very crucial to identify the impact of an individual or individuals in a social network, so that we can identify key individuals, or Alpha Users (term used in SNA), in a social network.

In this post we are going to see how to find the impact of an individual in a Social Network like Twitter, i.e., How many Twitter Users an individaul can influence via his/her Tweet upto N number of level, i.e., Followers of Followers of Followers… and so on. For, this…

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Knolx: Introduction to KnockoutJs


Hello all,

Knoldus organised a session on Friday, 07 October 2016. In that session, we had an introductory session on Knockout js.

Knockout is a JavaScript library that helps you to create a responsive display(UI). It is based on Model–View–Viewmodel (MVVM) pattern. It provides a simple two-way data binding mechanism between your data model and UI

The slides for the session are as follows:

And, you can also watch the video on youtube link is as follows:


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While programming in Scala we  often come across a term called Functor. A functor is an extremely simple but powerful concept. In this blog, let us discuss that in more detail.

Theoretically functor is a type of mapping between categories. Given two categories A and B, a functor F maps the objects or entities of A to objects or entities of B. We can simply call it a function of objects or entities.

In programming the functors come into play when we have types or values wrapped inside context or containers. This wrapping up inside context, blocks application of normal functions on the values. This happens because the result on application of function is dependent on the context.

The solution to above scenario is a function that knows how to apply functions to the values wrapped in a context. Internally speaking this function should have a potential to

  • unwrap(fetch) the value…

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Building Analytics Engine Using Akka, Kafka & ElasticSearch


In this blog , I will share my experience on building scalable, distributed and fault-tolerant  Analytics engine using Scala, Akka, Play, Kafka and ElasticSearch.

I would like to take you through the journey of  building an analytics engine which was primarily used for text analysis. The inputs were structured, unstructured and semi-structured data and we were doing a lot of data crunching using it. The Analytics engine was accessible by the rest-client and web-client(Built In with engine)  as shown in below diagram.

Here is a quick overview on technology stack :

  1. Play Framework  as Rest Server & Web Application  (Play is MVC  framework based on  lightweight, stateless and web friendly architecture.)
  2. Akka cluster as processing engine.(Akka is a toolkit and runtime for building highly concurrent,distributed, and resilient message driven applications on the JVM.)
  3. ClusterClient (It was contributed module) for communication with Akka cluster. It used to run on rest…

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