Decomposing applications for scalability and deployability - svcc sv_code_camp 2012

Decomposing applications for deployability and scalability

Chris Richardson

Author of POJOs in ActionFounder of the original CloudFoundry.com

@[email protected]://plainoldobjects.com/

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Presentation goal

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How decomposing applications improves

deployability and scalability and

How Cloud Foundry helps

About Chris

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(About Chris)

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About Chris()

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About Chris

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About Chris

http://www.theregister.co.uk/2009/08/19/springsource_cloud_foundry/

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vmc push About-Chris

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Developer Advocate for CloudFoundry.com

Signup at http://cloudfoundry.com

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Agenda§The (sometimes evil) monolith§Decomposing applications into services§How do services communicate?§Presentation layer design§How Cloud Foundry helps

Let’s imagine you are building an e-commerce application

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Tomcat

Traditional web application architecture

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Browser

WAR

MySQL Database

ShippingService

AccountingService

InventoryService

StoreFrontUI

developtestdeploy

Simple to

Apache

scale

But there are problems with a monolithic architecture

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Users expect a rich, dynamic and interactive experience

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Java Web Application

Browser

HTTP Request

HTML/Javascript

Old style UI architecture isn’t good enough

Real-time web ≅ NodeJS

Intimidates developers

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Obstacle to frequent deployments§Need to redeploy everything to change one component§Interrupts long running background (e.g. Quartz) jobs§Increases risk of failure

Fear of change

§Updates will happen less often§e.g. Makes A/B testing UI really difficult

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Overloads your IDE and container

16Slows down development

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Shipping team

Accounting team

Engineering

Obstacle to scaling development

E-commerce application

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WAR

Shipping

Accounting

InventoryService

StoreFrontUI

Shipping team

Accounting team

Inventory team

UI team


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Lots of coordination and communication required


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Requires long-term commitment to a technology

stack

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The scale cube

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X axis - horizontal duplication

Z axis

- data

parti

tionin

g

Y axis - functionaldecomposition

Scale

by sp

litting

simila

r

thing

s

Scale by splitting different things

Y-axis scaling - application level

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WAR

ShippingService

AccountingService

InventoryService

StoreFrontUI

Y-axis scaling - application level

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Store front web application

shipping web application

inventory web application

Apply X axis cloning and/or Z axis partitioning to each service

ShippingService

AccountingService

InventoryServiceStoreFrontUI

accounting web application

Partitioning strategies§Partition by verb, e.g. shipping service§Partition by noun, e.g. inventory service§Single Responsibility Principle§Unix utilities - do one focussed thing well

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Something of an art

Real world examples

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http://highscalability.com/amazon-architecture

Between 100-150 services are accessed to build a page.

http://techblog.netflix.com/

http://www.addsimplicity.com/downloads/eBaySDForum2006-11-29.pdf

http://queue.acm.org/detail.cfm?id=1394128

There are drawbacks

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Complexity

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See Steve Yegge’s Google Platforms Rant re Amazon.com

Multiple databases =

Transaction management challenges

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When to use it?

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In the beginning: •You don’t need it •It will slow you down

Later on:•You need it•Refactoring is painful

But there are many benefits§Scales development: develop, deploy and scale each service independently§Update UI independently§Improves fault isolation§Eliminates long-term commitment to a single technology stack

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Modular, polyglot, multi-framework applications

Two levels of architecture

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System-level

ServicesInter-service glue: interfaces and communication mechanismsSlow changing

Service-level

Internal architecture of each serviceEach service could use a different technology stackPick the best tool for the jobRapidly evolving

If services are small...§Regularly rewrite using a better technology stack§Adapt system to changing requirements and better technology without a total rewrite§Pick the best developers rather than best <pick a language> developers ⇒ polyglot culture

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Fred George “Developer Anarchy”

The human body as a system

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50 to 70 billion of your cells die each day

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Yet you (the system) remain you

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Can we build software systems with these characteristics?

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http://dreamsongs.com/Files/WhitherSoftware.pdf

http://dreamsongs.com/Files/DesignBeyondHumanAbilitiesSimp.pdf

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Inter-service communication options§Synchronous HTTP ⇔ asynchronous AMQP

§Formats: JSON, XML, Protocol Buffers, Thrift, ...

§Even via the database

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Asynchronous is preferred

JSON is fashionable but binary format is more efficient

StoreFrontUI

wgrus-store.war

AccountingService

wgrus-billing.war

InventoryService

wgrus-inventory.war

ShippingService

wgrus-shipping.war

MySQL

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RabbitMQ(Message Broker)

Asynchronous message-based communication

Benefits§Decouples caller from server§Caller unaware of server’s coordinates (URL)§Message broker buffers message when server is down/slow

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Drawbacks§Additional complexity of message broker §RPC using messaging is more complex

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Writing code that calls services

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The need for parallelism

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Service A

Service B

Service C

Service D

b = serviceB()

c = serviceC()

d = serviceD(b, c)

Call in parallel

Java Futures are a great concurrency abstraction

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http://en.wikipedia.org/wiki/Futures_and_promises

Akka’s composable futures are even better

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Using Akka futures

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def callB() : Future[...] = ...def callC() : Future[...] = ...def callD() : Future[...] = ...

val future = for { (b, c) <- callB() zip callC(); d <- callD(b, c) } yield d

val result = Await.result(future, 1 second)

http://doc.akka.io/docs/akka/2.0.1/scala/futures.html

Two calls execute in parallel

And then invokes D

Get the result of D

Spring Integration§Provides the building blocks for a pipes and filters architecture§Enables development of application components that are•loosely coupled•insulated from messaging infrastructure

§Messaging defined declaratively

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Handling failure

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Service A Service B

Errors happen in distributed systems

About Netflix

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> 1B API calls/day1 API call ⇒ average 6 service calls

Fault tolerance is essential

http://techblog.netflix.com/2012/02/fault-tolerance-in-high-volume.html

Use timeouts and retries

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Never wait forever

Errors can be transient ⇒ retry

http://techblog.netflix.com/2012/02/fault-tolerance-in-high-volume.html

Service A

Service B

Use per-dependency bounded thread pool

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Runnable 1

Runnable 2

Runnable ...

bounded queue

Task 1

Task 2

Task ...

bounded thread pool

Limits number of outstanding requests

Fails fast if service is slow or down

Use a circuit breakerHigh error rate ⇒ stop calling temporarily

Down ⇒ wait for it to come back up

Slow ⇒ gives it a chance to recover


On failureReturn cached data

Return default data

Fail fast


AvoidFailing

WorkerActor

Aspects + Actors

CallerDependency

InvokerAspect

DependencyStub

CircuitBreakerActor

WorkerActor

Implements circuit

breaker state machine

Equivalent of thread pool

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@DependencyProxy

@Service@DependencyProxy(circuitBreaker = "factualCircuitBreaker", timeoutInMilliseconds=750)class FactualRestaurantService extends RestaurantService { ...}

trait RestaurantService { def findNearbyRestaurants(location: Location) : Future[FindNearbyRestaurantResponse]}

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Aspect-based Async

@Aspectclass DependencyInvokingAspect {

@Pointcut("execution(* (@DependencyProxy *).*(..))") def dependencyProxyMethods {}

@Around("dependencyProxyMethods()") def invoke(jp: ProceedingJoinPoint) = { val a = AnnotationUtils.findAnnotation(jp.getTarget.getClass, classOf[DependencyProxy]) val actor = findActor(a) val timeout = Timeout(a.timeoutInMilliseconds milliseconds) actor.ask(InvokeDependency( () => jp.proceed())) (timeout) }

}

Ask actor to invoke jp.proceed() and return Future

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See https://github.com/cer/votemeeteat

for the Actor code

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Modular application

Choice of presentation layer technology

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NodeJS is the fashionable technology

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Why NodeJS?

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§Familiar Javascript

§High-performance, scalable event-driven, non-blocking I/O model

§Over 13,000 modules developed by the community

§Many JavaScript client frameworks have a NodeJS counterpart, e.g. socket.io

NodeJS example

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var http = require('http');var fs = require("fs");

http.createServer(function (req, res) { fs.readFile('somefile.txt', function (err, data) { if (err) throw err; res.writeHead(200, {'Content-Type': 'text/plain'}); res.end(data); });}).listen(1337, '127.0.0.1');

console.log('Server running at http://127.0.0.1:1337/');

Handle HTTP

request

Handle file read

NodeJS isn’t the only game in town

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JVM-based http://vertx.io/

A modern web application

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Browser

Service 1

Service 2

...

HTML 5Application

Socket.ioclient

Events

RESTful WS

Server Application

Socket.ioserver

Node JS

NodeJS - using RESTful WS and AMQP

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Node JS

Service

RabbitMQ Service

REST

AMQP AMQP

RESTRequests

Events

socket.io

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Tomcat

Original architecture

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Browser

WAR

MySQL Database

ShippingService

AccountingService

InventoryService

StoreFrontUI

Apache

Inventory Service

Shipping Service

NodeJS

Modern architecture

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RabbitMQ

NodeJS

Inventory Service

Shipping Service

Billing ServiceRedis

Inventory Database

Mongo Order Database

Standalone“headless” Spring/Java applications

Spring/Scala web

application

MySQL Customer Database

Desktop Browser Native Mobile application HTML5 mobile application

StoreUI StoreUI StoreUI

StoreUIJavascriptAsynchronous,

scalable communication

Traditional tools: monolithic applications

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Developing modular apps is more difficult

§Many more moving parts to manage•Platform services: SQL, NoSQL, RabbitMQ•Application services: your code§Who is going to setup the environments:•the developer sandbox?•...•QA environments?

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But Cloud Foundry helps...

Applica'on Service Interface

Data Services

Other Services

Msg Services

Easy polyglot application deployment and service provisioning

vFabric Postgres

vFabric RabbitMQTM

Additional partners services …

OSS community

Private Clouds

PublicClouds

MicroClouds

Multi-application manifest - part 1--- applications: inventory/target: name: inventory url: cer-inventory.chrisr.cloudfoundry.me framework: name: spring info: mem: 512M description: Java SpringSource Spring Application exec: mem: 512M instances: 1 services: si-rabbit: type: :rabbitmq si-mongo: type: :mongodb si-redis: type: :redis

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Path to application

Required platform services

Multi-application manifest - part 2 store/target: name: store url: cer-store.chrisr.cloudfoundry.me framework: name: spring info: mem: 512M description: Java SpringSource Spring Application exec: mem: 512M instances: 1 services: si-mongo: type: :mongodb si-rabbit: type: :rabbitmq

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Path to application

Required platform services

One command to create platform services and deploy application

$ vmc push Would you like to deploy from the current directory? [Yn]: Pushing application 'inventory'...Creating Application: OKCreating Service [si-rabbit]: OKBinding Service [si-rabbit]: OKCreating Service [si-mongo]: OKBinding Service [si-mongo]: OKCreating Service [si-redis]: OKBinding Service [si-redis]: OKUploading Application: Checking for available resources: OK Processing resources: OK Packing application: OK Uploading (12K): OK Push Status: OKStaging Application 'inventory': OK Starting Application 'inventory': OK Pushing application 'store'...Creating Application: OKBinding Service [si-mongo]: OKBinding Service [si-rabbit]: OKUploading Application: Checking for available resources: OK Processing resources: OK Packing application: OK 77

vmc push:•Reads the manifest file•Creates the required platform services•Deploys all the applications

Micro Cloud Foundry: new developer sandbox

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Open source Platform as a Service project

App Instances Services

10.04

A PaaS packaged as a VMware Virtual Machine

Use as a developer sandbox• Use the services from Junit integration tests• Deploy your application for functional testing• Remote debugging from STS

Using Caldecott to tunnel into your services

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Caldecott = TCP over HTTP

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Your computer

Caldecott gem

Cloud Foundry

Caldecott application Service

HTTPnative

protocol

Port NNN

Service client

nativeprotocol

Using Caldecott…$ vmc tunnel1: mysql-135e02: mysql1Which service to tunnel to?: 2Password: ********Stopping Application: OKRedeploying tunnel application 'caldecott'.Uploading Application: Checking for available resources: OK Packing application: OK Uploading (1K): OK Push Status: OKBinding Service [mysql1]: OKStaging Application: OK Starting Application: OK Getting tunnel connection info: OK

Service connection info: username : uMe6Apgw00AhS password : pKcD76PcZR7GZ name : d7cb8afb52f084f3d9bdc269e7d99ab50

Starting tunnel to mysql1 on port 10000.1: none2: mysqlWhich client would you like to start?: 2

…Using CaldecottLaunching 'mysql --protocol=TCP --host=localhost --port=10000 --

user=uMe6Apgw00AhS --password=pKcD76PcZR7GZ d7cb8afb52f084f3d9bdc269e7d99ab50'

Welcome to the MySQL monitor. Commands end with ; or \g.Your MySQL connection id is 10944342Server version: 5.1.54-rel12.5 Percona Server with XtraDB (GPL),

Release 12.5, Revision 188

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or itsaffiliates. Other names may be trademarks of their respectiveowners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

Running JUnit test with Caldecott

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Configure your test code to use port + connection info

Summary

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Monolithic applications are simple to develop and deploy

BUT have significant drawbacks

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Apply the scale cube

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X axis - horizontal duplicationZ ax

is - d

ata pa

rtitio

ning

Y axis - functionaldecomposition

§Modular, polyglot, and scalable applications§Services developed, deployed and scaled independently

Cloud Provide

r Interface

Applica'on Service Interface

Private Clouds

PublicClouds

MicroClouds

Data Services

Other Services

Msg Services

.js

Cloud Foundry helps...

Questions?

@crichardson [email protected]://slideshare.net/chris.e.richardson/

www.cloudfoundry.com

Decomposing applications for scalability and deployability - svcc sv_code_camp 2012

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