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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?

casoetan

"""
Marshmallow wrappers to produce GeoJSON instead of a flat dictionary.
"""
from flask_marshmallow import Marshmallow
import geoalchemy2
from geoalchemy2.shape import from_shape, to_shape
from marshmallow import fields, pre_load, post_dump, ValidationError
import marshmallow_sqlalchemy as msqla
from shapely import geometry

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Requirements

Minikube requires that VT-x/AMD-v virtualization is enabled in BIOS. To check that this is enabled on OSX / macOS run:

sysctl -a | grep machdep.cpu.features | grep VMX

If there's output, you're good!

Prerequisites

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// The Babylonian Method 
// http://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method
// @param n - the number to compute the square root of
// @param g - the best guess so far (can omit from initial call)
function squirt(n, g) {
    if (!g) {
        // Take an initial guess at the square root
        g = n / 2.0;
    }
    var d = n / g;              // Divide our guess into the number

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var sqrt = function(x) {
  var isGoodEnough = function(guess) {
    return Math.abs(guess * guess - x) / x < 0.001;
  };
  
  var improve = function(guess) {
    return (guess + x / guess) / 2;
  };
  
  var sqrIter = function(guess) {

casoetan

Converting mkv to mp4 with ffmpeg

Essentially just copy the existing video and audio stream as is into a new container, no funny business!

The easiest way to "convert" MKV to MP4, is to copy the existing video and audio streams and place them into a new container. This avoids any encoding task and hence no quality will be lost, it is also a fairly quick process and requires very little CPU power. The main factor is disk read/write speed.

With ffmpeg this can be achieved with -c copy. Older examples may use -vcodec copy -acodec copy which does the same thing.

These examples assume ffmpeg is in your PATH. If not just substitute with the full path to your ffmpeg binary.

Single file conversion example

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package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
)

func main() {

casoetan

package main
import (
        "fmt"
        "gopkg.in/mgo.v2"
        "gopkg.in/mgo.v2/bson"
)

func main() {
        session, err := mgo.Dial("localhost")
        if err != nil {

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What is this?

Following this guide will set up a local Elasticsearch with Kibana and Marvel using Homebrew and Homebrew Cask

Prerequisites

If you already have Java installed on your system, skip steps Install Cask and Install Java

If you already have Java and Homebrew installed on your system, skip steps Prerequisites, start at Install Elasticsearch and Kibana after running $ brew update

Install Homebrew

• $ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

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Fixing npm On Mac OS X for Homebrew Users

Installing node through Homebrew can cause problems with npm for globally installed packages. To fix it quickly, use the solution below. An explanation is also included at the end of this document.

Solution

This solution fixes the error caused by trying to run npm update npm -g. Once you're finished, you also won't need to use sudo to install npm modules globally.

Before you start, make a note of any globally installed npm packages. These instructions will have you remove all of those packages. After you're finished you'll need to re-install them.