Akshay Pratap Singh kodekracker

OpenSSL Playground

Certificates

Print Certificate ( crt file )

openssl x509 -in stackexchangecom.crt -text -noout

Print Certificate ( pem file )

openssl x509 -in cert.pem -text -noout

Print Certificate ( cer file )

openssl x509 -inform der -in foobar.cer -noout -text

Read part of Certificate

Ubuntu 16 – how to increase maximum file open limit ( ulimit -n )

If you are setting up nginx,chances are you will discover your worker_connections is at some low number, such as 1024. You can’t increase this number unless you increase kernel limit as well. First of all run cat /proc/sys/fs/file-max to discover your maximum limit.

abc@ubuntu:~$ cat /proc/sys/fs/file-max
1048576
abc@ubuntu:~$ ulimit -n
1024

Scaling your API with rate limiters

The following are examples of the four types rate limiters discussed in the accompanying blog post. In the examples below I've used pseudocode-like Ruby, so if you're unfamiliar with Ruby you should be able to easily translate this approach to other languages. Complete examples in Ruby are also provided later in this gist.

In most cases you'll want all these examples to be classes, but I've used simple functions here to keep the code samples brief.

Request rate limiter

This uses a basic token bucket algorithm and relies on the fact that Redis scripts execute atomically. No other operations can run between fetching the count and writing the new count.

A non-exhaustive list of WebGL frameworks and libraries. It is mostly for learning purposes as some of the libraries listed are outdated/not maintained anymore.

Engines and libraries

three.js: JavaScript 3D library
stack.gl: an open software ecosystem for WebGL, built on top of browserify and npm.
PixiJS: Super fast HTML 5 2D rendering engine that uses webGL with canvas fallback
Pex: Pex is a javascript 3d library / engine allowing for seamless development between Plask and WebGL in the browser.
Babylon.js: a complete JavaScript framework for building 3D games with HTML 5 and WebGL
Filament: Filament is a real-time physically based rendering engine for Android, iOS, Windows, Linux, macOS and WASM/WebGL
ClayGL: A WebGL graphic library helping you to

Install dlib and face_recognition on a Raspberry Pi

Instructions tested with a Raspberry Pi 2 with an 8GB memory card. Probably also works fine on a Raspberry Pi 3.

Steps

Download the latest Raspbian Jessie Light image. Earlier versions of Raspbian won't work.

Write it to a memory card using Etcher, put the memory card in the RPi and boot it up.

	CREATE OR REPLACE FUNCTION pseudo_encrypt(VALUE bigint) returns bigint AS $$
	DECLARE
	l1 bigint;
	l2 bigint;
	r1 bigint;
	r2 bigint;
	i int:=0;
	BEGIN
	l1:= (VALUE >> 32) & 4294967295::bigint;
	r1:= VALUE & 4294967295;

	#define _GNU_SOURCE
	#include <errno.h>
	#include <sched.h>
	#include <signal.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <sys/mount.h>
	#include <sys/stat.h>
	#include <sys/syscall.h>
	#include <sys/types.h>

	/* global createImageBitmap */

	function loadImageWithImageTag(src) {
	return new Promise((resolve, reject) => {
	const img = new Image;
	img.crossOrigin = '';
	img.src = src;
	img.onload = () => { resolve(img); };
	img.onerror = () => { reject(img); };
	});

	-- Create a group
	CREATE ROLE readaccess;

	-- Grant access to existing tables
	GRANT USAGE ON SCHEMA public TO readaccess;
	GRANT SELECT ON ALL TABLES IN SCHEMA public TO readaccess;

	-- Grant access to future tables
	ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readaccess;

	user web;

	# One worker process per CPU core.
	worker_processes 8;

	# Also set
	# /etc/security/limits.conf
	# web soft nofile 65535
	# web hard nofile 65535
	# /etc/default/nginx