Web Basics

URL - Uniform Resource Locator

http://www.google.com/
protocol + host + path

Query Parameters (GET parameters) http://example.com/foo?p=100&q=meat

Fragment Used to reference a part of the page http://example.com/foo#fragment

Port

By default, it equals 80 http://example.com:80/toys?p=foo#blah

HTTP Request

http://example.com/foo GET /foo HTTP/1.1 //This is the request line Host: www.example.com // Followed by headers User-Agent: chrome

HTTP Response

HTTP/1.1 200 OK // Status line Date: xxx xxx xxx Server: Apache xxx Content-Type: text/html Content-Length: 1539

404 Not Found 500 Server Error

Servers

The purpose of the server is to response to HTTP requests

There are two types of content

• Static - images, files etc
• Dynamic - made on the fly by web applications

HTTPS

API

JSON Escaping

Caching

if request is in cache:
    return cache[request] // cache hit
else 
    r = db_read()         // cache miss
    cache[request] = r
    return r

Stateless

• stateless is the key to scaling
• there's no state between requests
• apps are now interchangable
• apps can be scaled independent of cache and db
• we can store state in: cookies, DB, memcached

Why do we separate our services?

• So they can be scaled independently
• To increase fault tolerance
• So they can be updated independently