Year: 2015

Live Like a Hydra: Thoughts on how to get stronger when things are chaotic. #2 The Chaos Monkey — Medium

Netflix has a server architecture that currently serves a pretty high percentage of all of the internet’s traffic, due to their streaming video service.

One of the most interesting things about their server architecture is that they routinely attack their own systems. They have a tool called Chaos Monkey that randomly disables their own production instances to make sure they can survive that common type of failure without any customer impact.

Because there are several ways in which servers can fail, they’ve also employed a fleet of monkeys that attack all manner of servers — some that are too slow, some that aren’t connected up to the proper server groups, some that just look weird, etc. And finally, there’s a Chaos Gorilla that doesn’t just turn off individual servers, but occasionally wipes out an entire availability zone, as if Godzilla had destroyed an entire portion of the country.

The philosophy is simple: by building a server architecture that expects failure, the system as a whole can learn how to withstand bigger and tougher obstacles even if they don’t know exactly when or how they will occur in real life.

Meet Margaret Hamilton, the badass ’60s programmer who saved the moon landing – Vox

Apollo was also a major software project. Astronauts used the Apollo Guidance Computer, which was placed in both the command module and the lunar module, for navigation assistance and to control the spacecraft, and someone needed to program it.

The software for the guidance computer was written by a team at the MIT Instrumentation Laboratory (now the Draper Laboratory), headed up by Margaret Hamilton. Here’s an amazing picture of her next to the code she and her colleagues wrote for the Apollo 11 guidance computer that made the moon landing possible.

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The process of actually coding in the programs was laborious, as well. The guidance computer used something known as “core rope memory”: wires were roped through metal cores in a particular way to store code in binary. “If the wire goes through the core, it represents a one,” Hamilton explained in the documentary Moon Machines. “And around the core it represents a zero.” The programs were woven together by hand in factories. And because the factory workers were mostly women, core rope memory became known by engineers as “LOL memory,” LOL standing for “little old lady.”

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