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Showing posts from 2021

The FB outage

 This outage has caused considerable noise everywhere. It was quite discomforting for me because during the whole conversation nobody bothered to understand the gravity of the issue. I don't expect end users to understand the issue. But this is going to be a blogpost for all of those in the tech field, Such an event can happen how much ever chaos engineering, best of the tech jargon we implement in the stack To all my Site Reliability Engineer friends, Site Up is our first priority. I myself said many a times outage is news and SREs should prevent outage. But I'm afraid this is leading to a cult in the industry who despises outages and takes no learnings from it. I don't know what has happened in Facebook. I can explain a scenario which may or may not be right but that can definitely show the gravity of the issue. Let's draw a probable Facebook architecture Disclaimer I don't work at Facebook. So this might not be how facebook routes traffic. This is based on my exp

Covid in India

The second wave of COVID is creating havoc across the country. Though we could factor in innumerable reasons why we had let our guards down and taken by surprise with the second wave, one of the most important reasons is apathy and casual attitude of we the citizens. The more sooner we get this wave plateau, we can start taking the control. There are many models and forecasts out there when we would reach our peak. All of this is similar to astrology because there are lot of variables like enforcing lockdown, availability of oxygen/beds, rate of vaccination. Now I'm going to act like a soothsayer and explain my model. And going to explain whether my model works or not our system is overwhelmed and we need to give it an immediate relief.  I'm calculating R factor based on my understanding  R=(no. of cases in day d)/(no. of cases in day d-5)  This R tracks growth every 5th day assuming a person showing symptoms on a day d could have got the viral load passed on d-5. To achieve a

More on Memory

 A post almost after 2 years!!! One common question I get asked is, "what is the reference I follow for troubleshooting an issue at hand". I would not be able to give an answer to the question directly as most of the times, I won't have even a single reference material handy. It's not a self boasting article. It's an article describing how knowledge we gather at random places help during an issue. Let's dissect a memory usage issue in Linux I faced recently and see how the triage shaped up. One of our processes was getting repeated ENOMEM when it was trying to call malloc for some reason despite the box had plenty of unused RAM. Lets see how the triage went through I didn't understand in my Operating systems course what a virtual memory is. I did convincing myself that virtual memory is physical memory + swap(in a way correct but not completely) I attended an interview in 2013, where the Director of the division asked me when you do malloc do you get physi