Josef Strzibny strzibny

Optimistic Locking assumes that a database transaction conflict is very rare to happen. It uses a version number of the record to track the changes. It raise an error when other user tries to update the record while it is lock.

usage

Just add a lock_version column to the table you want to place the lock and Rails will automatically check this column before updating the record.

Pessimistic locking assumes that database transaction conflict is very likely to happen. It locks the record until the transaction is done. If the record is currently lock and the other user make a transaction, that second transaction will wait until the lock in first transaction is release.

usage

Realtime Notifications with ActionCable

In this episode we're going to be adding realtime notifications into your app using ActionCable. We've talked about notifications a few times in the past and we used AJAX polling for that. 95% of the time, polling is the solution that would be recommended for it.

But if you're looking for a good introduction into ActionCable then this is a decent one because we're only really using it for one way from the server side to the client side.

Getting started

So to get started we're starting with an app that has Bootstrap installed and then we created a Main controller with an index view which is where we will list our Notifications as for this example.

Before we generate our channels let's install a few things

Crystal vs Node.js Websocket Benchmark

Crystal 0.9.1 with Kemal

require "kemal"

ws "/" do |socket|
  socket.on_message do |message|
 end

	Source: https://www.cyberciti.biz/tips/linux-unix-bsd-nginx-webserver-security.html

	This page collects hints how to improve the security of nginx web servers running on Linux or UNIX-like operating systems.

	Default Config Files and Nginx Port

	/usr/local/nginx/conf/ or /etc/nginx/– The nginx server configuration directory and /usr/local/nginx/conf/nginx.conf is main configuration file.
	/usr/local/nginx/html/ or /var/www/html– The default document location.
	/usr/local/nginx/logs/ or /var/log/nginx – The default log file location.
	Nginx HTTP default port : TCP 80

	##
	# Parallel test Runner for Rails
	#
	# This is a spike implementation for multi-process parallel testing with Rails.
	# Only works with SQLite3 right now, and doesn't clean up.
	#
	# Here is an example of how to use it:
	#
	# ```ruby
	# require 'forking_executor'

	defmodule ScoutApm.Absinthe.Plug do
	alias ScoutApm.Internal.Layer

	def init(default), do: default

	def call(conn, _default) do
	ScoutApm.TrackedRequest.start_layer("Controller", action_name(conn))

	conn
	\|> Plug.Conn.register_before_send(&before_send/1)

	#!/bin/bash
	# james shubin, agplv3+
	# pause until key press and then continue
	# https://ttboj.wordpress.com/2017/01/06/ten-minute-hacks-process-pause-resume

	if [ ! "$#" -eq 1 ]; then
	echo "Usage: `basename $0` <process>"
	echo "Pauses process until key press and then continues!"
	exit 1
	fi

-# Stop all containers
-docker stop `docker ps -qa`
-# Remove all containers
-docker rm `docker ps -qa`
-# Remove all images
-docker rmi -f `docker images -qa `
-# Remove all volumes

	defmodule KeyValueStore do
	use GenServer

	@me __MODULE__

	@moduledoc """

	Implement a simple key-value store as a server. This
	version creates a named server, so there is no need
	to pass the server pid to the API calls.

	Priority Queues
	═══════════════

	━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
	INSERT DEL-MIN MIN DEC-KEY DELETE MERGE
	binary log n log n 1 log n log n n
	binomial 1 log n 1 log n log n log n
	Fibonacci 1 log n† 1 1† log n† log n
	Pairing 1† log n† 1† 1† log n† 1†
	Brodal-Okasaki 1 log n 1 1 log n 1