giang12

#System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

##Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

giang12

// Require our core node modules.
var util = require("util");

// Export the constructor function.
exports.AppError = AppError;

// Export the factory function for the custom error object. The factory function lets
// the calling context create new AppError instances without calling the [new] keyword.
exports.createAppError = createAppError;

giang12

ּ_בּ
בּ_בּ
טּ_טּ
כּ‗כּ
לּ_לּ
מּ_מּ
סּ_סּ
תּ_תּ
٩(×̯×)۶
٩(̾●̮̮̃̾•̃̾)۶

giang12

#!/usr/bin/env ruby
#/ Usage: <progname> [options]...
#/ How does this script make my life easier?
# ** Tip: use #/ lines to define the --help usage message.
$stderr.sync = true
require 'optparse'

# default options
flag    = false
option  = "default value"

giang12

Below are the Big O performance of common functions of different Java Collections.


List                 | Add  | Remove | Get  | Contains | Next | Data Structure
---------------------|------|--------|------|----------|------|---------------
ArrayList            | O(1) |  O(n)  | O(1) |   O(n)   | O(1) | Array
LinkedList           | O(1) |  O(1)  | O(n) |   O(n)   | O(1) | Linked List
CopyOnWriteArrayList | O(n) |  O(n)  | O(1) |   O(n)   | O(1) | Array

giang12

Studying for a Tech Interview Sucks, so Here's a Cheat Sheet to Help

This list is meant to be a both a quick guide and reference for further research into these topics. It's basically a summary of that comp sci course you never took or forgot about, so there's no way it can cover everything in depth. It also will be available as a gist on Github for everyone to edit and add to.

Data Structure Basics

###Array ####Definition:

• Stores data elements based on an sequential, most commonly 0 based, index.
• Based on tuples from set theory.

giang12

---
- name: Setup SBC
  hosts: all
  #become: true
  #become_user: root
  gather_facts: false

  vars:
    #New user to be created
    new_user: newuser

giang12

Multiplatform (amd64 and arm) Kubernetes cluster setup

The official guide for setting up Kubernetes using kubeadm works well for clusters of one architecture. But, the main problem that crops up is the kube-proxy image defaults to the architecture of the master node (where kubeadm was run in the first place).

This causes issues when arm nodes join the cluster, as they will try to execute the amd64 version of kube-proxy, and will fail.

It turns out that the pod running kube-proxy is configured using a DaemonSet. With a small edit to the configuration, it's possible to create multiple DaemonSets—one for each architecture.

Steps

Follow the instructions at https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/ for setting up the master node. I've been using Weave Net as the network plugin; it see

giang12

# Ask for the user password
# Script only works if sudo caches the password for a few minutes
sudo true

# Install kernel extra's to enable docker aufs support
# sudo apt-get -y install linux-image-extra-$(uname -r)

# Install docker-compose
COMPOSE_VERSION=v`git ls-remote https://github.com/docker/compose | grep refs/tags | grep -oE "[0-9]+\.[0-9][0-9]+\.[0-9]+$" | sort --version-sort | tail -n 1`
BIN_URL=https://github.com/docker/compose/releases/download/${COMPOSE_VERSION}/docker-compose-`uname -s`-`uname -m`