decomposing applications for deployability and scalability (cf india july/august 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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dsply ‘About Chris’;

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RPG

(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

developtestdeployscale

Simple to

Apache

But there are problems

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Users expect a rich, dynamic and interactive experience on mobile devices and desktop

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Java Web Application

Browser

HTTP Request

HTML/Javascript

Old style UI architecture isn’t good enough

Real-time web ≅ NodeJS

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 15

Overloads your IDE and container

16Slows down development

Obstacle to scaling development

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!=Scalable development

WAR

Shipping

Accounting

InventoryService

StoreFrontUI

Forces teams to synchronize development efforts Teams need to coordinate updates

Requires long-term commitment to a technology stack

Switching technology stack ⇒ touches entire application Painful and rarely done Makes it difficult to incrementally adopt newer technologies You end up being stuck with the technology you started with

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3 dimensions to scaling

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X axis - horizontal duplicationZ ax

is - d

ata pa

rtitio

ning

Y axis - functionaldecomposition

Scale by cloning

Scale

by sp

litting

simila

r thin

gsScale by splitting different things

Y axis scaling - functional partitioning Splits monolithic application into a set of services Each service implements a set of related functionality Partitioning schemes:•Partition functionality by noun or by verb•Single Responsibility Principle•Unix utilities - do one focussed thing well

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Something of an art

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

billing web application

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 Complexity: development, deployment, etc. Multiple databases ⇒ transaction management challenges Deciding when to use it• In the beginning: you don’t need it and it will slow you down•When you do need it: refactoring existing code is painful

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

But there are many benefits Scales development: develop, deploy and scale each service

independently Improves fault isolation Enforces well defined interfaces between components Eliminates long-term commitment to a single technology

stack

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Modular, polyglot, multi-framework applications

Two levels of architecture System level•Defines the inter-service glue: interfaces and

communication mechanisms•Slow changing

Service level•Defines the internal architecture of each service•Far fewer constraints on technology•Each service could use a different technology stack•Pick the best tool for the job•Rapid evolving

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Versus

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 Multiple collaborating services ⇒ need a communication

mechanism Many choices:•Synchronous ⇔ asynchronous•Transports: HTTP, AMQP, ...•Formats: JSON, XML, Protocol Buffers, Thrift, ...•Even via the database

Distributed application ⇒ error handling strategies

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

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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Composable futures Problem:•Service A needs to call services B and C and then D•Makes sense to call B and C parallel•Yet most concurrency APIs are low-level, error-prone etc

Solution:•Use Akka composable futures = really nice abstraction

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val futureB = callB()val futureC = callC()

val futureD = for { b <- futureB.mapTo[SomeType] c <- futureC.mapTo[SomeType] d <- callD(b, c) } yield d

val result = Await.result(futureD, 1 second). asInstanceOf[SomeOtherType]

http://doc.akka.io/docs/akka/2.0.1/scala/futures.htmlhttp://en.wikipedia.org/wiki/Futures_and_promises

Two calls execute in parallel

And then invokes D

Get the result of D

Spring Integration

Builds on Spring framework

Implements EAI patterns = high-level of abstraction for building message based applications

Provides the building blocks for a pipes and filters architecture

• Pipes = message channels

• Filters = endpoints that filter, transform, route messages and integrate with external messaging infrastructure

Enables development of components that are

• loosely coupled

• insulated from underlying messaging infrastructure

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Handling failure

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Service A Service B

Errors happen in distributed systems

Use timeouts and retries

Never wait foreverErrors can be transient ⇒ retry

41http://techblog.netflix.com/2012/02/fault-tolerance-in-high-volume.html

Service A

Service B

Use per-dependency bounded thread pool


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

Avoids calling service that has issues

Down ⇒ wait for it to come back up

Slow ⇒ gives it a chance to recover


On failure - don’t fail tooReturn cached dataReturn default data

Invoke custom error handler


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Modular application

Choice of presentation layer technology+

Redeploy UI frequently/independently

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NodeJS is the fashionable technology

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Many JavaScript client frameworks have a NodeJS counterparte.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

Eventssocket.io

Updating the UI is easy

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Update the UI independently of rest of system Easily run A/B tests Enables fast iteration of the UI

http://theleanstartup.com/principles

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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 Uploading (5K): OK Push Status: OKStaging Application 'store': OK Starting Application 'store': ... 60

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

ServiceHTTP native

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 Monolithic applications are simple to develop and deploy

BUT have significant drawbacks

Applying the scale cube

Decomposes your application into services Enables scaling for transactions and data volumes Tackles application complexity Enables scaling for development Enables frequent, independent deployments Make it easy to leverage other technologies

AND

Cloud Foundry simplifies the development and deployment of modular, service-based applications 67

Questions?

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

www.cloudfoundry.com

decomposing applications for deployability and scalability (cf india july/august 2012)

Technology

set of services

chris http

comamazonarchitecture

e commerce application

interservice glue

different technology

better technology stack

presentation layer design