EWD: Simplifying Web Application Architecture

EWD:

Simplifying WebApplication Architecture

Rob TweedM/Gateway Developments Ltd

http://www.mgateway.comTwitter: @rtweed

A bit about me• 1980s:

– Lead Mumps developer at Royal MarsdenHospital, London: Hospital Information System

• Early 1990s: Management consultant at

Touche Ross, London• Major NHS Networking project for Dept of Health

• Mid-1990s – present:

– Caché/Mumps web app framework developer

– Javascript expert

– Internet technology industry watcher

A bit about me

• Pioneer of web development for Mumps

& Caché

– WebLink & WebLink Developer

• Sold to InterSystems: 1996

– Consultant for early CSP design

– Assisted most of InterSystems' major

customers worldwide on Web Application

design & development

A bit about me

• Author of EWD

– 2004 – present

– Advanced web/ajax development framework

• EWD:

– Supports the largest Internet-facing Caché-based

web applications

• World's largest Caché-based web app:

– Quest Diagnostics Care360 "EziOrder"

» 30,000+ concurrent users

» 500,000 test requests/day

Why Do I Despair?

• This is the industry-standard way it's done, right?

• So what's the problem?

Why Do I Despair?

• This is the industry-standard way it's done,

right?

• Yes, but nobody seems to ask the basic

question:

– How on earth did something so simple (the web) end

up being such a complex mess of stacks and layers?

– Web apps were supposed to make things simpler!

What the "Experts" miss

• The technology on which VistA was built (Mumps) turns out to also be a technology that could have been designed specifically as a web application platform– Almost no layers or moving parts needed– The entire web application development framework,

runtime AND application(s) can run on a single technical platform

• Mumps/Caché: the world's most misunderstood database technology

So why is this kind of nonsense the

accepted norm for web apps?

When it could be as simple as this:

Browser

Web

Server

(Apache/

IIS)

Gate

way

Caché

http/

https

WebLin

kin

terfa

ce

Caché

CS

P in

terfa

ce

Caché

Gate

way

EWDRuntime

VistA

Page Scripts

ie: the "experts" propose this:

When we could have this:

Why does this matter anyway?

Why does this matter anyway?

• 1 day of coding will cost

13 days of maintenance

• Fewer moving parts and

layers means that one person can understand

the entire application

• Remember: the people

who will maintain the application are rarely the

original developers

So why is this kind of nonsense the

accepted norm for web apps?

To understand:

• We need to go back through the history of the web

Why was the web successful?

• "Good enough" at the right price

– Free!

– Simple architecture

– Simple to build web pages

• No special tools required

• Anyone could create a web site

– Simple to access web pages

– Basic graphical UI

• Designers loved it and pushed its limits

"Static" web architecture

Browser Web Server File Store

Apache

IIS

HTTP

Request

"Static" web architecture

Browser Web Server File Store

Apache

IIS

HTTP

Response

Step2: Dynamic Pages

• Instead of fixed data in my pages, I want to display the latest figures in a table

– Dynamically generate the data in the

document

How to do this?

Browser Web Server File StoreHTTP

Response

Database

Dynamically

build a page of

HTML

Enter CGI


Response

Database

CGI Interface

But databases don't have a

scripting environment, so:


Response

Database

CGI Interface

Scripting

Language

eg Perl

Step 3

• This is ~1995, the era of Client/Server

• Lots of problems emerging:

– Deployment and maintenance of thick clients

– Complexity of development:

• Logic split between client & server

• Multiple languages & layers (sounds familiar??)

Step 3

• Why not use the browser as a universally-available standard smart UI?

• Move our application logic all back to the back-end

• Simulate an interactive UI session via a succession of generated HTML pages

• Web Apps were born!

Problem 1:

• HTTP is stateless

• An interactive user application requires maintenance of state

– Persistent information available throughout

the user's session

Problem 2:

• Browser still just communicates with the web server using just HTTP requests

• So, how to deal with security?

– How can we uniquely and reliably recognise

the incoming request as being from the

person they claim to be?

– How can we protect an individual's session

from malicious access?

Combine Problems 1 & 2:

• How can we reliably determine who the user is from the incoming request?

• How can we determine what they want to do on the basis of their request?

• How can we recreate their session state before handling their request?

The layers start to appear


Response

Corporate

RDBMS

CGI Interface

Security

Management

State

Management

HTML Page

Generation

Security Management


Response

Corporate

RDBMS

CGI Interface

Security

Management

State

Management

HTML Page

Generation

User

Credentials?

State Management

• Requirement:

– High-performance, highly scalable key/value

store

– Ideally not just simple key/value store

– RDBMS too heavy, slow

– State management database requires

something more dynamic and free-form

Enter In-memory Key/Value Stores

• memcache

• Redis

For more complex session data:

• NoSQL "Document" databases:

– MongoDB

• NoSQL Columnar databases

– Hadoop

– Cassandra

More layers appear


Response

Corporate

RDBMS

CGI Interface

Security

Management

State

Management

HTML Page

Generation

User

Credentials?NoSQL

Database(s)

CGI too slow, so fast APIs

Browser Apache File StoreHTTP

Response

Corporate

RDBMS

ISAPI / FastCGI

Security

Management

State

Management

HTML Page

Generation

User

Credentials?NoSQL

Database(s)

"Proper" scripting languages

• Perl too weird and clunky

• "Professional" languages needed

– Enter .Net and Java

• While we're at it, lets encapsulate all those other layers in our own special flavours

• "Hide" all that complexity by creating our own new complexity

Let's rationalise app design

• Model/View/Controller (MVC)

• Mapping URLs to resources (dynamic pages)

• Model for the data

• Views define the returned content

• Controllers access the database and business logic

And so we end up with, eg: J2EE

A complete nightmare

• Everyone pretends to understand it

– Nobody actually does

• It's supposedly designed to be manageable

– Nobody really knows how to manage it because nobody really understands it

• If programmers can barely understand it, what

chance do designers have?

– Design, not programming, is what makes an application a success

Result

• Timescales slip

• Budgets soar

• Staff turnover:– the people who originally designed it have

gone and new people can't understand what they've inherited

• Version 1 maybe eventually gets delivered

• Don't hold your breath for versions 2 and later!

Web Applications

• They were supposed to be simpler than Client/Server, right?

• The industry has managed to turn them into as big a mess!

A better way?

Wind back to 1994

• I realised that web pages could be generated dynamically

• The browser could provide all the UI capabilities that we'd required for clinical applications at the Royal Marsden Hospital

Mumps: the World's Least

Understood database

• Databases normally need to be accessed and manipulated via a separate scripting language

• Mumps & Caché are almost unique in that they have an integrated, tightly-coupled scripting language

– Mumps database

– Mumps language

Mumps: Tailor-made for the web

• Very high peformance, highly scalable language & database

• Interpreted, "fast and loose" language

• Dynamic, schema-free hierarchical database– "Universal" NoSQL capabilities:

• Key/value store

• Document store

• Columnar store

• Graph store

• Native XML Database / DOM

• Relational & Object (aka Caché)

Mumps: the layers disappear


Response

ISAPI / FastCGI

Caché / Mumps

Web Application

Management

EnvironmentCorporate Applications

Session Storage

EWD: back to simplicity

• High-level abstraction for app design– To the developer, it's as if you're designing using

static pages

– Native XML DOM-based compilation stage

• State & Session management happens automatically

• No baffling MVC complexity

• Simple, intuitive concepts

• High-speed development

• Simple maintenance

EWD makes it as simple as this:

Browser

Web

Server

(Apache/

IIS)

Gate

way

Caché

http/

httpsW

ebLin

kin

terfa

ce

Caché

CS

P in

terfa

ce

Gate

way

EWD

Runtime

VistA

* Page Scripts

* EWD

Pages

EWD Session

Store

Caché or GT.M

What about non-Mumps

integration?

• Several alternatives:– Ensemble

• Integration engine built on top of Cache

• Adaptors for most other databases and languages

• EWD is 100% compatible with Ensemble

– Web Service access• EWD can consume external web services

– Behave as an HTTP client

– Node.js (server-side Javascript) opens up new alternatives

• ewdGateway.js: Node.js gateway module for EWD

• Use other Node.js modules for integrating other DBMS

Ensemble Example:

Browser

Web

Server

(Apache/

IIS)

Gate

way

Caché

WebLin

kin

terfa

ce

Caché

CS

P in

terfa

ce

Gate

way

EWDRuntime

VistA

Page Scripts

Ensemble

Adaptor DoD

EWDPages

EWD SessionStore

iEHR

• You don't need to go down the industry-standard route

• EWD is tried-and-tested technology

• Direct integration with ExtJS v4 and Sencha Touch (for mobile)

• It is demonstrably orders of magnitude faster to develop with and cheaper and simpler to maintain

Which would you feel safest in?

EWD: Simplifying Web Application Architecture

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