Hongbo Zhen bobzhen

Virtual Hosts on nginx (CSC309)

When hosting our web applications, we often have one public IP address (i.e., an IP address visible to the outside world) using which we want to host multiple web apps. For example, one may wants to host three different web apps respectively for example1.com, example2.com, and example1.com/images on the same machine using a single IP address.

How can we do that? Well, the good news is Internet browsers

Install a new Ruby with rbenv on Mac OS (and make yourself a superhero)

If you're doing stuff with Ruby on a Mac, e.g. installling Jekyll or something, by default you'll end up having to use the sudo command to do stuff, since the permission to modify the default config is not available to your user account.

This sucks and should be avoided. Here's how to fix that.

Installing a new Ruby

To make this better, we are going install a new, custom Ruby. This used to be a big, scary thing, but thanks to the awesome tools Homebrew and rbenv, it's a snap.*

A word of warning: you will have to use Terminal to install this stuff. If you are uncomfortable with text, words, and doing stuff with your computer beyond pointing and hoping, this may not work well for you. But if that's the case, I'm not sure why you were trying to use Ruby in the first place.

JSX Spread Attributes

If you know all the properties that you want to place on a component a head of time, it is easy to use JSX:

  var component = <Component foo={x} bar={y} />;

Mutating Props is Bad, mkay

Elixir installation guide

Version numbers should be the ones you want. Here I do it with the last ones available at the moment of writing.

The simplest way to install elixir is using your package manager. Sadly, at the time of writing only Fedora shows the intention to keep its packages up to date. There you can simply sudo dnf install erlang elixir and you are good to go.

Anyway, if you intend to work with several versions of erlang or elixir at the same time, or you are tied to a specific version, you will need to compile it yourself. Then asdf is your best friend.

To enable the precompilation of all non.js/.css assets within vendor/assets just add this to config/initializers/assets.rb:

Rails.application.config.assets.precompile << Proc.new { |path, fn| fn =~ /vendor\/assets/ && !%w(.js .css).include?(File.extname(path)) }

Be aware that this will precompile ALL non .js/.css assets that you have there, some plugins or libraries might have .txt or other files around, and those would end up into your precompiled list also.

If you need to precompile images only, you could use this:

Rails.application.config.assets.precompile += %w(*.png *.jpg *.jpeg *.gif)

	# lib/tasks/db.rake
	namespace :db do

	desc "Dumps the database to db/APP_NAME.dump"
	task :dump => :environment do
	cmd = nil
	with_config do \|app, host, db, user\|
	cmd = "pg_dump --host #{host} --username #{user} --verbose --clean --no-owner --no-acl --format=c #{db} > #{Rails.root}/db/#{app}.dump"
	end
	puts cmd

	# Access number
	cat production.log \| grep "^Processing" \| wc \| awk '{print $1}'

	# Each IP access number
	cat production.log \| grep “^Processing” \| awk ‘{print $4}’ \| uniq -c

	# Independent IP number
	cat production.log \| grep "^Processing" \| awk '{print $4}' \| uniq \| wc \| awk '{print $1}'
	cat production.log \| grep “^Processing” \| awk ‘{print $4}’ \| uniq \| wc -l

	So i was using Rails 4.1 with Unicorn v4.8.2 and when i tried to deploy my app it doesn't start properly and into the unicorn.log file i found this error message:

	"app error: Missing `secret_key_base` for 'production' environment, set this value in `config/secrets.yml` (RuntimeError)"

	After a little research i found that Rails 4.1 change the way to manage the secret_key, so if we read the secrets.yml file located at exampleRailsProject/config/secrets.yml (you need to replace "exampleRailsProject" for your project name) you will find something like this:

	# Do not keep production secrets in the repository,
	# instead read values from the environment.
	production:
	secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>

	#!/usr/bin/env sh

	# checks to see if running
	launchctl list \| grep elasticsearch

	launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.elasticsearch.plist
	launchctl remove homebrew.mxcl.elasticsearch

	pkill -f elasticsearch

	See question on stack overflow: http://stackoverflow.com/questions/28595636/rails-4-how-to-give-alias-names-to-includes-and-joins-in-active-record-que

	- Model Student and model Teacher are both STI models with super class model User
	- Model Story is a STI model with super class model Task
	- includes() and joins(), both fails

	Rails alias naming convention (includes() and joins())

	- One model as parameter
	- is base model (includes(:users))