Introduction

Clojure’s documentation describes Transducers as composable algorithmic transformations. They are transformations which are independent of input or output and they compose without awareness of input or creation of aggregate values.

When talking about transducers, we should look at the original thing that gave rise to this abstraction. The reduction

A reducing function is essentially any function that you can pass to a reduce call. This function is supposed to take the result so far, generally known as the accumulator and the new value and generate a new result. So a reducing function is

accumulated-result, input -> accumulated-result

While a transducer…


This blog is the second part of a blog series on Understanding the Jepsen toolkit for Distributed systems testing. I would encourage you to go through part 1 before continuing on here.

Major components of a Jepsen test

Generators

A Jepsen history is a list of operations — invocations and completions. A generator’s job is to specify what invocations to perform, and when. In a sense, a generator’s output becomes a history as Jepsen incrementally applies it to a database.

Conceptually, then, a generator is a graph of events, some of which have not yet occurred. Some events are invocations: these are the operations the generator will…


Introduction

Jepsen is a suite of open-source testing tools aimed at verifying the safety of Distributed systems like databases, queues and consensus implementations. Jepsen also includes a series of amazing conference talks and blog posts which offer keen insights into the correctness of such systems under effects of faults like network partitions, split brains etc. To find such errors in the distributed systems, Jepsen uses something known as consistency models to ensure that observed effects of operations are consistent with a given model.

What is a consistency model ?

This gives a very good overview of all the important concepts that formulate a consistency model. Briefly put…


It was friday I think, I don’t really remember. Yeah it was friday. It was booze night and i had a few too many that day. I was high as a bird ! It was around 1 in the morning and I was returning home when I saw her. I probably shouldn’t have stopped but she looked like a real mess. I figured I ought to help her. It was the booze clouding my judgement. So I did stop. And here’s what happened because I did …

I walked up to her to ask what the problem was. She was…


Dear diary,

As i write this, i know i am going to die any day now. He is surely going to kill me. I have seen it in his eyes. I have seen the hatred, i have seen the hurt and most importantly, the revenge which seethes his soul.

As i look back on my life, all i remember is May 26th 1980. That was the day my fate was sealed. As i heard the words “we the jury find the defendant guilty of voluntary manslaughter and arson and hereby sentence him to life imprisonment”, i was almost too calm…


It was a typical summers afternoon in a small town in Texas. The heat was unbearable. But he had no choice. He had a job to do. Twenty jobs, to be precise. Doug was a tv repair guy for an electronics store. He was your typical average joe. A hard grind through life, struggling to make ends meet. The only family he had was his mother with whom he lived. But lately, even she was becoming a burden for him. Constantly ill, never happy, always crying and shouting and writhing in the pain of the cancerous disease that afflicted her…


I am Jean Bernaad and i am the best tight-rope walker in the world. And as i plummet to my death, i can see the most wonderful rocky valley calling me into its ever wider arms. The valley almost seems a friend. A friend who is longing for me, pulling me towards it, what it doesnt realise is that it might kill me in the process. Not its fault really, its me who has been teasing it, taunting it almost daring it to kill me. It all started a few years ago when a friend of mine, Jose, dared me…


As he walks slowly, almost trudging towards his house, Vikram realizes something. It was 3 years ago to this day that all of this had started. This was the day everything started going down hill. This was the day that fate decided to deal its cruel hand. The hand was revealed much later, with the calm and composure of a hired assassin; and the kill was almost complete now. This was the day, 3 years ago that his journey had started. A journey towards his ultimate end. …


As he poured his daily drink, his favorite jazz record was his only companion. That was all he ever needed actually. At least thats what he had convinced himself of. Sitting in his rickety old armchair, he contemplated what he was about to do. His final act. His final duty.

Azrael thought about his first day on the job. His first day as an executioner at the state prison. It was a rainy winter afternoon. The murky darkness of the windows seemed to echo the soul of the man standing in front of him. It was a deranged man who…


I am like a thief who is afraid of the dark,
of the deathly silence, the gnarly dogs’ bark.

I scourge for wealth in the day, never venture out in the night,
when the darkened souls awaken, ravenous and hungry for a fight.

They call it a revolution, an uprising, a spring.
It is but a war, a heinous mutiny, against our beloved king.

This too shall pass, to such storms, we leaders do not sway.
And when the blinding day comes again, we shall make them pay !

Rhishikesh Joshi

Free radical, programmer, polyglot, coffee lover…

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