Dat Nguyen nguyendat

The introduction to Reactive Programming you've been missing

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

Change your database RDS instance security group to allow your machine to access it.
- Add your ip to the security group to acces the instance via Postgres.
Make a copy of the database using pg_dump
- $ pg_dump -h <public dns> -U <my username> -f <name of dump file .sql> <name of my database>
- you will be asked for postgressql password.
- a dump file(.sql) will be created
Restore that dump file to your local database.
- but you might need to drop the database and create it first
- $ psql -U <postgresql username> -d <database name> -f <dump file that you want to restore>

the database is restored

Instructions

CloudFlare is an awesome reverse cache proxy and CDN that provides DNS, free HTTPS (TLS) support, best-in-class performance settings (gzip, SDCH, HTTP/2, sane Cache-Control and E-Tag headers, etc.), minification, etc.

Make sure you have registered a domain name.
Sign up for CloudFlare and create an account for your domain.
In your domain registrar's admin panel, point the nameservers to CloudFlare's (refer to this awesome list of links for instructions for various registrars).
From the CloudFlare settings for that domain, enable HTTPS/SSL and set up a Page Rule to force HTTPS redirects. (If you want to get fancy, you can also enable automatic minification for text-based assets [HTML/CSS/JS/SVG/etc.], which is a pretty cool feature if you don't want already have a build step for minification.)
If you

A curated list of AWS resources to prepare for the AWS Certifications

A curated list of awesome AWS resources you need to prepare for the all 5 AWS Certifications. This gist will include: open source repos, blogs & blogposts, ebooks, PDF, whitepapers, video courses, free lecture, slides, sample test and many other resources.

Snippets collected/distilled from gists/blog posts/etc. Combined here for fellow web-searchers -- goal is to have an easy/minimal sink for in-app use, and then forward that stream in another process.

Read camera, push to UDP sink (usually from appsrc, here v4l2 camera):

$ gst-launch-1.0 -vvvv v4l2src ! 'video/x-raw, width=640, height=480, framerate=30/1' ! videoconvert ! x264enc pass=qual quantizer=20 tune=zerolatency ! rtph264pay ! udpsink port=1234

Visualize above:

$ gst-launch-1.0 -vvv udpsrc port=1234 ! "application/x-rtp,media=(string)video,clock-rate=(int)90000,encoding-name=(string)H264" ! rtph264depay ! h264parse ! decodebin ! videoconvert ! xvimagesink sync=false

Lambdas, Functions, Functors and Monads

Intro

If you've been exposed to lambdas (whether in Java or Kotlin), you already know at least the basics of what lambdas are, the syntax for using them, that they're more succinct than instantiating anonymous classes etc etc.

Rather than talking about that, I figured we would talk about functions and lambdas on a higher level.

I think most of us are familiar with map and, having used it quite a bit, have an intuitive understanding of what any given call to map will do.

Does anyone know a bit more about map, what it is and where it came from?

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

	<NotepadPlus>
	<UserLang name="Gradle" ext="gradle">
	<Settings>
	<Global caseIgnored="yes" />
	<TreatAsSymbol comment="yes" commentLine="yes" />
	<Prefix words1="no" words2="no" words3="no" words4="no" />
	</Settings>
	<KeywordLists>
	<Keywords name="Delimiters">"'0"'0</Keywords>
	<Keywords name="Folder+"></Keywords>

	package com.vaughandroid.test.espresso.idlingresources;

	import android.app.Activity;
	import android.os.Handler;
	import android.support.annotation.IdRes;
	import android.support.annotation.NonNull;
	import android.support.test.espresso.*;
	import android.view.View;

	import java.lang.ref.WeakReference;

	private val HEX_CHARS = "0123456789ABCDEF".toCharArray()

	fun ByteArray.toHex() : String{
	val result = StringBuffer()

	forEach {
	val octet = it.toInt()
	val firstIndex = (octet and 0xF0).ushr(4)
	val secondIndex = octet and 0x0F
	result.append(HEX_CHARS[firstIndex])