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A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,

Redis in Production at Smyte

To be clear we continue to run many Redis services in our production environment. It’s a great tool for prototyping and small workloads. For our use case however, we believe the cost and complexity of our setup justifies urgently finding alternate solutions.

Each of our Redis servers are clearly numbered with a current leader in one availability zone, and a follower in another zone.
The servers run ~16 different individual Redis processes. This helps us utilize CPUs (as Redis is single-threaded) but it also means we only need an extra 1/16th memory in order to safely perform a BGSAVE (due to copy-on-write), though in practice it’s closer to 1/8 because it’s not always evenly balanced.
Our leaders do not every run BGSAVE unless we’re bringing up a new slave which is carefully done manually. Since issues with the slave should not affect the leader and new slave connections might trigger an unsafe BGSAVE on the leader, slave Redis processes are set to not automatically rest

What I Wish I'd Known About Equity Before Joining A Unicorn

Disclaimer: This piece is written anonymously. The names of a few particular companies are mentioned, but as common examples only.

This is a short write-up on things that I wish I'd known and considered before joining a private company (aka startup, aka unicorn in some cases). I'm not trying to make the case that you should never join a private company, but the power imbalance between founder and employee is extreme, and that potential candidates would

security and hardening options for systemd service units

A common and reliable pattern in service unit files is thus:

NoNewPrivileges=yes
PrivateTmp=yes
PrivateDevices=yes
DevicePolicy=closed
ProtectSystem=strict

Mono Repository Tool Comparison

For Web Client / Front End Projects

(That Probably Use HTML, CSS, and JS)

I made a list of 20 things I might want out of a monorepo tool for a Design System to use as a basis for comparing some of the options including Lerna, Northbrook, and Rush.

⚠️ Northbrook's author says the project is pretty dead and now uses Lerna.

	import React from 'react'
	import { findDOMNode } from 'react-dom'

	if (typeof window !== 'undefined' && 'scrollRestoration' in window.history) {
	history.scrollRestoration = 'manual'
	}

	export const useRestoreScroll = () => ({
	renderRootContainer: (props) => (
	<RestoreScrollContainer {...props}/>


	import React from 'react'

	const bgStyles = {
	strokeWidth: 3,
	strokeLinejoin: 'round',
	strokeLinecap: 'round',
	fill: 'none',
	stroke: '#c3fdff'
	}

	import React from 'react';

	const toPromise = (load) => (new Promise((resolve) => (
	load(resolve)
	)));

	class LazilyLoad extends React.Component {

	constructor() {
	super(...arguments);

	// This is an example of how to fetch external data in response to updated props,
	// If you are using an async mechanism that does not support cancellation (e.g. a Promise).

	class ExampleComponent extends React.Component {
	_currentId = null;

	state = {
	externalData: null
	};

	// handy method to create a Higher Order Component out of a
	// Render Prop Component (like a Context.Consumer).
	// handles, statics, displayName, refs, and value forwarding

	function createHOCFromRenderProp({prop, Consumer}) {
	return Component => {
	function Wrapper(props, ref) {
	return (
	<Consumer>
	{value => <Component {...{...props, [prop]: value, ref}} />}