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In order to make our application, highly available and fault tolerant, I have been researching a lot on best disaster recovery strategy for Kafka. In earlier relational systems, such as MySQL or Oracle, it was standard to have an active-passive cluster where in the application does reads and writes to a primary cluster. This primary cluster is asynchronously replicated to a secondary cluster. The application falls back to the secondary cluster incase the primary cluster...

Continuing article on Kotlin for Java Developers, Let’s continue the differences: Inheritance Singletons when instead of switch Mutable variables inside lambda With keyword Inheritance Classes are final by default. We have to use open keyword to tell compiler to indicate that class is extensible Singletons In Kotlin, singletons can be simply defined using object keyword object CompanyCommunications { val currentYear = Year.now().value fun getTagLine() = "Our company rocks" fun getCopyrihtLine() = "Copyright"; } Static keyword...

Continuing article on Kotlin for Java Developers, Let’s continue the differences: Access Modifiers Defining Classes and Constructors Multiple constructors Generate Getters and Setters Data classes Extension Functions Access Modifiers Default top level visibility is public whereas its package private in java There is no restriction to have class names and filenames so its possible to declare multiple public classes in single Kotlin file There is something called private class in Kotlin which means only classes...

I have been learning Kotlin in my free time and I must say I have been glued to it since then due to its conciseness and addressing some of the issues which are there in Java. Hence, In this part I post, we will look at differences between Kotlin and Java from the programmer’s perspective. We will cover the runtime aspects and interoperability in the later posts. Equality differences No checked exceptions Wrapper classes Traditional...

Recently, I have been involved in an effort which required migrating a database with millions of rows from MySQL to Azure CosmosDB. Those who are new to CosmosDB, it is a Microsoft’s globally distributed, multi-model database service. The good thing about CosmosDB is that it provides data access using the familiar API’s in form of SQL, MongoDB, Cassandra etc. We used the MongoDB driver for our use-case, so essentially it was a RDBMS to NOSQL...

I have been playing with Apple’s CreateML. Specifically, I have been following Apple’s tutorial on creating text classification models The exact code as described in article doesn’t work, atleast on OSX 10.14 Mojave. The snippet I have been using is: import Cocoa import CreateML import NaturalLanguage let data = try MLDataTable(contentsOf: URL(fileURLWithPath: "/Users/madhur/Desktop/iOS/ML/twitter-sanders-apple3.csv")) let (trainingData, testingData) = data.randomSplit(by: 0.8, seed: 5) let sentimentClassifier = try MLTextClassifier(trainingData: trainingData, textColumn: "text", labelColumn: "class") The last line throws...

Recently, one of my Macbook Pro 2014 model started showing this information on battery usage: Naturally, it got me worried as I had lot of code and data which was not backed up. However, at the same time I was curious to know how Apple is able to determine the degradation in battery health. Is it a function of age, discharge / charging time OR something else? Upon further debugging, turns it its a function...

I got thrown up with some more tasks to perform on shell. First was to extract numbers from long list of text. For ex, you have text as : [ NumberLong(90), NumberLong(123), NumberLong(218), NumberLong(221), NumberLong(294), NumberLong(317), NumberLong(319), NumberLong(322), NumberLong(328), NumberLong(344), NumberLong(348) ] To simple extract numbers from this file, we’ll use pcregrep command to capture the regex group and output it. #!/bin/bash cat input.txt | pcregrep -o1 -i '([0-9]+)' > output.txt Second was to compare...

Recently, I was required to generate multiple UUID’s and pass onto HTTP request as a paremeter. I thought of using Python or Node.js for this purpose, but thought why not use a plain old shell. But, is there a way to generate UUID in shell? Turns out, there is using uuidgen command which works on both Linux and MacOS. Hence, using the power of another command called seq, and xargs we can achieve many powerful...

I have always been fan of well assembled desktop systems. Its a joy to carefully pick each component of your personal computer and assemble it to pick best performance. The current rig which I use is listed here on PCPartPicker It is also very important to continously monitor the performance of such system so as to make sure they are running in optimum systems. Especially important is CPU and GPU temperatures. With latest software and...