Digests » 243

this week's favorite

An education Python implementation of blockchain

This is an experimental notebook that implements most of the concepts of a bitcoin-like blockchain in python. It is NOT secure neither a real blockchain and you should NOT use this for anything else than educational purposes. Regardless of the financial benefits/drawbacks of bitcoin, the underlying technology is very interesting and the original paper is relatively easy to grasp.

Scaling Slack’s Job Queue

Slack uses a job queue system for business logic that is too time-consuming to run in the context of a web request. This system is a critical component of our architecture, used for every Slack message post, push notification, URL unfurl, calendar reminder, and billing calculation. On our busiest days, the system processes over 1.4 billion jobs at a peak rate of 33,000 per second. Job execution times range from a few milliseconds to (in some cases) several minutes.

Oh shit, git!

Git is hard: screwing up is easy, and figuring out how to fix your mistakes is fucking impossible. Git documentation has this chicken and egg problem where you can't search for how to get yourself out of a mess, unless you already know the name of the thing you need to know about in order to fix your problem.

Mining Bitcoin with pencil and paper: 0.67 hashes per day

I decided to see how practical it would be to mine Bitcoin with pencil and paper. It turns out that the SHA-256 algorithm used for mining is pretty simple and can in fact be done by hand. Not surprisingly, the process is extremely slow compared to hardware mining and is entirely impractical. But performing the algorithm manually is a good way to understand exactly how it works.

This is strictly a violation of the TCP specification

522 error on CloudFlare indicates a connection issue between our edge server and the origin server. Most often the blame is on the origin server side - the origin server is slow, offline or encountering high packet loss. Less often the problem is on our side. In the case I was debugging it was neither. The internet connectivity between CloudFlare and origin was perfect. No packet loss, flat latency. So why did we see a 522 error?

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