kapkaev

#!/usr/bin/ruby

require 'net/ssh'
require 'pp'

def fetch(host)
  data = []
  Net::SSH.start(host, 'virool') do |ssh|
    index_folders = ssh.exec!("ls -d /var/lib/kafka/*").split("\n")
    data = index_folders.flat_map do |ifolder|

kapkaev

Introduction to Kafka

Kafka acts as a kind of write-ahead log (WAL) that records messages to a persistent store (disk) and allows subscribers to read and apply these changes to their own stores in a system appropriate time-frame.

Terminology:

• Producers send messages to brokers
• Consumers read messages from brokers
• Messages are sent to a topic

kapkaev

Getting Started with NPM (as a developer)

If you haven't already set your NPM author info, now you should:

npm set init.author.name "Your Name"
npm set init.author.email "you@example.com"
npm set init.author.url "http://yourblog.com"

npm adduser

kapkaev

# Sample implementation of quicksort and mergesort in ruby
# Both algorithm sort in O(n * lg(n)) time
# Quicksort works inplace, where mergesort works in a new array

def quicksort(array, from=0, to=nil)
    if to == nil
        # Sort the whole array, by default
        to = array.count - 1
    end

kapkaev

t = 236 # seconds
Time.at(t).utc.strftime("%H:%M:%S")
=> "00:03:56"

# Reference
# http://stackoverflow.com/questions/3963930/ruby-rails-how-to-convert-seconds-to-time

kapkaev

RAILS_ENV=production rake db:setup
# produces the error below.....hmmm.....it's a no-worky
psql:/yourprojectpath/yourproject/db/structure.sql:29: ERROR:  could not open extension control file "/usr/share/postgresql/9.1/extension/hstore.control": No such file or directory

# hstore postgresql extension needs to be installed, so....
sudo apt-get install postgresql-contrib

# now your extension should be available to enable so log in with psql
psql -d yourproject_production -U yourdbuser -W

kapkaev

files = Dir["./**/*"]

files.each do |file|
  next if File.directory?(file)
  
  words = []
  begin
    File.read(file).scan /[\u0400-\u04FF\-]+/ do |match|
      words << match
    end

kapkaev

Share Counts

I have always struggled with getting all the various share buttons from Facebook, Twitter, Google Plus, Pinterest, etc to align correctly and to not look like a tacky explosion of buttons. Seeing a number of sites rolling their own share buttons with counts, for example The Next Web I decided to look into the various APIs on how to simply return the share count.

If you want to roll up all of these into a single jQuery plugin check out Sharrre

Many of these API calls and methods are undocumented, so anticipate that they will change in the future. Also, if you are planning on rolling these out across a site I would recommend creating a simple endpoint that periodically caches results from all of the APIs so that you are not overloading the services will requests.

Twitter

kapkaev

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

kapkaev

Getting zsh to work in ubuntu is weird, since sh does not understand the source command. So, you do this to install zsh

wget https://github.com/robbyrussell/oh-my-zsh/raw/master/tools/install.sh -O - | zsh

and then you change your shell to zsh

chsh -s `which zsh`

and then restart