rgreenjr

-- show running queries (pre 9.2)
SELECT procpid, age(clock_timestamp(), query_start), usename, current_query 
FROM pg_stat_activity 
WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%' 
ORDER BY query_start desc;

-- show running queries (9.2)
SELECT pid, age(clock_timestamp(), query_start), usename, query 
FROM pg_stat_activity 
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%' 

paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

spalladino

# Backup
docker exec CONTAINER /usr/bin/mysqldump -u root --password=root DATABASE > backup.sql

# Restore
cat backup.sql | docker exec -i CONTAINER /usr/bin/mysql -u root --password=root DATABASE

chanks

Turning PostgreSQL into a queue serving 10,000 jobs per second

RDBMS-based job queues have been criticized recently for being unable to handle heavy loads. And they deserve it, to some extent, because the queries used to safely lock a job have been pretty hairy. SELECT FOR UPDATE followed by an UPDATE works fine at first, but then you add more workers, and each is trying to SELECT FOR UPDATE the same row (and maybe throwing NOWAIT in there, then catching the errors and retrying), and things slow down.

On top of that, they have to actually update the row to mark it as locked, so the rest of your workers are sitting there waiting while one of them propagates its lock to disk (and the disks of however many servers you're replicating to). QueueClassic got some mileage out of the novel idea of randomly picking a row near the front of the queue to lock, but I can't still seem to get more than an an extra few hundred jobs per second out of it under heavy load.

So, many developers have started going straight t

phpdude

        location /resize {
                alias /tmp/nginx/resize;
                set $width 150;
                set $height 100;
                set $dimens "";

                if ($uri ~* "^/resize_(\d+)x(\d+)/(.*)" ) {
                        set $width  $1;
                        set $height $2;
                        set $image_path $3;

zman0900

Running Unifi Controller in systemd-nspawn with cloud-init

This uses Ubuntu's server cloud image as a stateless container to run the UBNT Unifi Controller software. Configuration data is stored in a directory outside the container. Cloud-init is used to automatically set up the container image, so a new version can be dropped in with minimal effort. This should work with pretty much any modern Linux distro with systemd.

Setup

Systemd-nspawn prefers to store its machines on btrfs, so if your /var/lib/machines is not currently btrfs, you should create one and mount it there. Otherwise it will automatically create an image file at /var/lib/machines.raw and mount it.

Create a device

alexpchin

Alex's Rails Cheat Sheet

I think the most confusing thing that I have found about Ruby on Rails so far has been the transition from (trying to) write code myself to the use of the fabled "Rails Magic". So, to help my own understanding of a few core Ruby on Rails concepts, I have decided to write something on what I think is a CRITICAL topic... the idea of Convention over Configuration and why (in my mind) it is the most important thing that helps Rails become magic!

(This may be a topic that we cover in more detail in class but as I said, I'm writing this for my own understanding... I hope it helps someone else understand things too... Perhaps you can give me a hand when I'm crying next week!)

##Convention over configuration ###What does this "actually" mean...

Mag81

Hacking the SamKnows Whitebox

The SamKnows Whitebox is a free router (TP-Link TL-WDR3600) provided by SamKnows to gather internet speed statistics. Ok that's great, but any person with a small amount of hacker's spirit will want to hack it to install some custom firmware to take advantage of the two gigantic antennas on the back, the USB ports and everything else.

Step 1 : Debug mode

Root access can be obtained via a "debug mode" on the router giving you a direct root shell via telnet, amazingly simple.

• Disconnect the Whitebox from the internet.
• Connect your computer directly to the Whitebox via Ethernet to one of the four ethernet ports on the Whitebox.
• Configure your computer's IP settings to "Manual" setting the computer's IP address to 192.168.1.2, the Subnet Mask to 255.255.255.0 and the Gateway to 192.168.1.1.
• Turn off the Whitebox.

Warry

How to make faster scroll effects?

• Avoid too many reflows (the browser to recalculate everything)
• Use advanced CSS3 for graphic card rendering
• Precalculate sizes and positions

Beware of reflows

The reflow appens as many times as there are frames per seconds. It recalculate all positions that change in order to diplay them. Basically, when you scroll you execute a function where you move things between two reflows. But there are functions that triggers reflows such as jQuery offset, scroll... So there are two things to take care about when you dynamically change objects in javascript to avoid too many reflows:

spikegrobstein

upstream plex-upstream {
	# change plex-server.example.com:32400 to the hostname:port of your plex server.
	# this can be "localhost:32400", for instance, if Plex is running on the same server as nginx.
	server plex-server.example.com:32400;
}

server {
	listen 80;

	# server names for this server.