Andrew Ry RyAndrew

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

Clarify and agree on the scope of the system

User cases (description of sequences of events that, taken together, lead to a system doing something useful)
- Who is going to use it?
- How are they going to use it?

Letsrobot.tv / Run My Robot Overlay Guide

Both of these methods expect a PNG image with transparency to be the same size as your video feed ( 640x480 by default ). It is possible to blend images at different resolutions with alternate commands but beyond the scope of this document.

Static video overlay

Requires no modification to FFMPEG
Add overlayCommand and change the videoCommandLine in send_video.py:

staticOverlayCommand = '-f image2 -i /home/pi/runmyrobot/images/hud.png -filter_complex "[0:v]format=argb,geq=r=\'r(X,Y)\':g=\'g(X,Y)\':b=\'b(X,Y)\':a=\'0.7*alpha(X,Y)\'[overlay]; [1:v][overlay]overlay"'

Exporting your 2FA tokens from Authy to transfer them into another 2FA application

IMPORTANT - Update regarding deprecation of Authy desktop apps

Past August 2024, Authy stopped supported the desktop version of their apps:
See Authy is shutting down its desktop app | The 2FA app Authy will only be available on Android and iOS starting in August for details.

And indeed, after a while, Authy changed something in their backend which now prevents the old desktop app from logging in. If you are already logged in, then you are in luck, and you can follow the instructions below to export to tokens.

If you are not logged in anymore, but can find a backup of the necessary files, then restore those files, and re-install Authy 2.2.3 following the instructions below, and it should work as expected.

	<?php

	/*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

	//Demo sketch
	//This sketch will output distance into via the UART port

	//port assignment
	//change as may be necessary

	const int trigger = 6;
	const int echo = 7;
	float distance;

	#!/bin/bash --debugger
	set -e

	BRANCH="master"
	if grep -q BCM2708 /proc/cpuinfo; then
	echo "RPI BUILD!"
	RPI="1"
	fi

	[ -n "$1" ] && BRANCH=$1

	// Run this in the F12 javascript console in chrome
	// if a redirect happens, the page will pause
	// this helps because chrome's network tab's
	// "preserve log" seems to technically preserve the log
	// but you can't actually LOOK at it...
	// also the "replay xhr" feature does not work after reload
	// even if you "preserve log".

	window.addEventListener("beforeunload", function() { debugger; }, false)

	# All nginx configurations can go here
	files:
	# This creates a file at the address below on the beanstalk instance
	/etc/nginx/conf.d/proxy.conf:
	mode: "000644"
	owner: root
	group: root
	content: \|
	upstream nodejs {
	server 127.0.0.1:8081;

	Mar 12, 2018 update: due to issues found internally, we added back 2 features:

	Printing-Client
	Windows-Defender-Features

	-------
	In the recent blog we shared that we removed a number of features to further reduce the size of the Windows Server Core container base image.
	https://techcommunity.microsoft.com/t5/containers/a-smaller-windows-server-core-container-with-better-application/ba-p/382412.

	Below is that list of features we removed. Let us know if you have any concern or share your feedback with us how this has worked for you. Thanks.

	#!/bin/bash

	mkdir postgres
	cd postgres

	docker volume create --driver local --name=pgvolume
	docker volume create --driver local --name=pga4volume

	docker network create --driver bridge pgnetwork