Khaja Minhajuddin minhajuddin

Effective Engineer - Notes

By Edmond Lau
Highly Recommended 👍
http://www.theeffectiveengineer.com/

What's an Effective Engineer?

They are the people who get things done. Effective Engineers produce results.

Adopt the Right Mindsets

How to recover lost Python source code if it's still resident in-memory

I screwed up using git ("git checkout --" on the wrong file) and managed to delete the code I had just written... but it was still running in a process in a docker container. Here's how I got it back, using https://pypi.python.org/pypi/pyrasite/ and https://pypi.python.org/pypi/uncompyle6

Attach a shell to the docker container

Install GDB (needed by pyrasite)

apt-get update && apt-get install gdb

Raspberry pi dashboard

This is what we did to setup a few dashboards at platanus

You'll need

Raspberry Pi
Dashing Service
Wifi stick (optional)

Let's Encrypt on Ubuntu 14.04, nginx with webroot auth

This document details how I setup LE on my server. Firstly, install the client as described on http://letsencrypt.readthedocs.org/en/latest/using.html and make sure you can execute it. I put it in /root/letsencrypt.

As it is not possible to change the ports used for the standalone authenticator and I already have a nginx running on port 80/443, I opted to use the webroot method for each of my domains (note that LE does not issue wildcard certificates by design, so you probably want to get a cert for www.example.com and example.com).

Configuration

For this, I placed config files into etc/letsencrypt/configs, named after <domain>.conf. The files are simple:

	curl --include \
	--no-buffer \
	--header "Connection: Upgrade" \
	--header "Upgrade: websocket" \
	--header "Host: example.com:80" \
	--header "Origin: http://example.com:80" \
	--header "Sec-WebSocket-Key: SGVsbG8sIHdvcmxkIQ==" \
	--header "Sec-WebSocket-Version: 13" \
	http://example.com:80/

	// ActiveTable - a bookmarklet to make tables sortable and editable

	function init() {
	var aHrows = getHrows();
	var numHrows = aHrows.length;

	var aHidden = getHiddenColumns();
	ATpopup = document.createElement("div");
	ATpopup.style.cssText = "position: absolute; visibility: hidden; padding: 0; font-family: Arial; background-color: rgba(255, 255, 255, 0.9); border-radius: .5em; text-align: center; box-shadow: .05em .05em .5em #00C;";
	ATpopup.innerHTML = "<a href='sort' title='sort' onclick='sortColumn(); return false'><img border=0 src='http://stevesouders.com/images/sort_up_down.png' style='padding-top: 0.2em;'></a><br><a href='hide' style='color: #C00; font-family: monospace; font-size: 1.5em; text-decoration: none;' title='hide' onclick='hideColumn(); return false'>x</a>"; // TODO - use protocol-less URL for img

	How to convert existing phoenix app to an umbrella app.
	https://elixir-lang.slack.com/archives/phoenix/p1472921051000134


	chrismccord [10:14 PM]
	@alanpeabody yes, it's straightforward

	[10:14]
	1) mix new my_umbrella --umbrella

	[Unit]
	Description=Keeps a tunnel to 'remote.example.com' open
	After=network.target

	[Service]
	User=autossh
	# -p [PORT]
	# -l [user]
	# -M 0 --> no monitoring
	# -N Just open the connection and do nothing (not interactive)

	defmodule Config do
	@moduledoc """
	This module handles fetching values from the config with some additional niceties
	"""

	@doc """
	Fetches a value from the config, or from the environment if {:system, "VAR"}
	is provided.

	An optional default value can be provided if desired.

	defmodule HttpRequester do
	use GenServer

	def start_link(_) do
	GenServer.start_link(__MODULE__, nil, [])
	end

	def fetch(server, url) do
	# Don't use cast: http://blog.elixirsips.com/2014/07/16/errata-dont-use-cast-in-a-poolboy-transaction/
	timeout_ms = 10_000