T. Mjoen tmjoen

HTTP and related specifications

This gist is deprecated in favor of https://github.com/ninenines/cowboy/blob/master/doc/src/guide/specs.asciidoc which has a formatted version at https://ninenines.eu/docs/en/cowboy/2.0/guide/specs/

HTTP

IANA Registries

Using OTP's observer (appmon replacement) remotely

$ ssh remote-host "epmd -names"
epmd: up and running on port 4369 with data:
name some_node at port 58769

Note the running on port for epmd itself and the port of the node you're interested in debugging. Reconnect to the remote host with these ports forwarded:

$ ssh -L 4369:localhost:4369 -L 58769:localhost:58769 remote-host

Falsehoods programmers believe about prices

You can store a price in a floating point variable.
All currencies are subdivided in 1/100th units (like US dollar/cents, euro/eurocents etc.).
All currencies are subdivided in decimal units (like dinar/fils)
All currencies currently in circulation are subdivided in decimal units. (to exclude shillings, pennies) (counter-example: MGA)
All currencies are subdivided. (counter-examples: KRW, COP, JPY... Or subdivisions can be deprecated.)
Prices can't have more precision than the smaller sub-unit of the currency. (e.g. gas prices)
For any currency you can have a price of 1. (ZWL)
Every country has its own currency. (EUR is the best example, but also Franc CFA, etc.)

WAL-E needs to be installed on all machines, masters and slaves.

How to install WAL-E

Only one machine, the master, writes WAL segments via continuous archiving. The configuration for the master postgresql.conf is:

archive_mode = on
archive_command = 'envdir /etc/wal-e.d/env wal-e wal-push %p'
archive_timeout = 60

	# This code is based on tutorial by slicktechies modified as needed to use oauth token from Twitch.
	# You can read more details at: https://www.junian.net/2017/01/how-to-record-twitch-streams.html
	# original code is from https://slicktechies.com/how-to-watchrecord-twitch-streams-using-livestreamer/

	import requests
	import os
	import time
	import json
	import sys
	import subprocess

	# ATTENTION: This is now supported in plug_cowboy as of 2.1.0:
	# https://hexdocs.pm/plug_cowboy/Plug.Cowboy.Drainer.html

	defmodule DrainStop do
	@moduledoc """
	DrainStop Attempts to gracefully shutdown an endpoint when a normal shutdown
	occurs. It first shuts down the acceptor, ensuring that no new requests can be
	made. It then waits for all pending requests to complete. If the timeout
	expires before this happens, it stops waiting, allowing the supervision tree
	to continue its shutdown order.

	defmodule EventWatcher do
	use Application

	def start(_type, _args) do
	import Supervisor.Spec, warn: false

	children = [
	worker(GenEvent, [[name: EventWatcher.GenEvent]], [id: :event_manager]),
	supervisor(EventWatcher.Watcher.Supervisor, [], [id: :watcher_supervisor])
	]

	// Alerts
	@include alert-variant($background, $border, $text-color);

	// Background Variant
	@include bg-variant($parent, $color);

	// Border Radius
	@include border-top-radius($radius);
	@include border-right-radius($radius);
	@include border-bottom-radius($radius);

	<!DOCTYPE HTML>
	<html>
	<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title>Bootstrap Masonry Template</title>
	<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css">
	<link rel="stylesheet" href="style.css">
	<link rel="stylesheet" href="http://fonts.googleapis.com/css?family=PT+Sans+Caption:400,700">

	# to generate your dhparam.pem file, run in the terminal
	openssl dhparam -out /etc/nginx/ssl/dhparam.pem 2048