Azure vs. Google App Engine

Platform-as-a-Service

Microsoft Windows Azure:

Transaction Processing and Availability

13.04.23 1TUM Informatik III: Datenbanksysteme Iwan Gulenko



Availability

Conclusion

degree of detail


Cloud Hierarchy

InfrastructureServer · Storage

IaaSPlatform

OS & Development Platform


PaaSApps

PlatformOS & Development Platform


SaaS


IaaS PaaS SaaS

Provided service • Virtual machines and tools • Templates for virtual machines

• Software platform • Standard app(s)

Characteristics • Any OS / app installable

• Applications developed, deployed & managed on SW platform

• Usage of app• Customization of app

Benefits of PaaS over…

+ Less maintenance costs+ Security

+ flexibility + full control over app

Drawbacks of PaaS over…

- underlying hardware not accessable- Pricing

- costs for development and maintenance of app

Cloud Hierarchy

· FIREWALL · FIREWALL · FIREWALL · FIREWALL · FIREWALL · FIREWALL · FIREWALL · FIREWALL ·

Intr

anet

Inte

rnet

CustomerApplication

Customer

Vendor

IT of your company

Cloud


Architecture

Beware of Buzzword

Bingo:=

Storage


Storage

Queues -Background work processing-Publish/subscribe principle

RDBMS - Subset of SQL Server functionalities

Blobs – Large Data StoreDrives – NTFS Formatted Page Blobs (new)

Tables - Very Fast / Scalable Storage

<key, value>


Storage

Name Birthday

Alice 10.10.1980

Bob 12.04.1987

Carl 02.03.1979

Favorite Food

Pizza

Flexible schema:

Massive scalability through partitions

UML visualization:


Use Case: Event management web site Frequent user query: “List all events in my city.”

Storage

SeattleNY San

Fr.

Server 1

Server 1

Server 2

Load Balancing

Storage


Storage

Queues -Background work processing-Publish/subscribe




<key, value>


21

21

11

11

C1C1

C2C2

11

11

21

21

3340

40

Producers Consumers

P2P2

P1P1

30

30

11

11

21

21

10

10

20

20

Storage

11

11

20

20

Message M on Queue: Amount += 10 1. Worker Role A takes message M from Queue ( M

becomes invisible for other Worker Role instances) 2. Amount+= 10 3. VM Fails

After 30 sek : Message M visible to all Worker Role instances

1. Worker Role B takes message M from Queue ( M becomes invisible for other Worker Role instances)

2. Amount += 10 (we will be rich ) 3. Worker Role B removes message M from queue


Storage


21

21

11

11

C1C1

C2C2

11

11

21

21

3340

40

Producers Consumers

P2P2

P1P1

30

30

11

11

21

21

10

10

20

20

Storage

11

11

20

20

Make messages idempotent e.g. Implement optimistic concurrency (with timestamps)

At-least-Once

UPDATE Table1 Set Col1 = @NewCol1Value, Set Col2 = @NewCol2Value, Set Col3 = @TimestampWHERE Col1 = @OldCol1Value AND Col2 = @OldCol2Value AND Col3 = @Timestamphttp://msdn.microsoft.com/en-us/library/aa0416cz(VS.80).aspx


Storage

Storage


Storage

Queues -Background work processing-Publish/subscribe




<key, value>


Application

InternetAzure Cloud

InternetAzure Cloud

LBLB

TDS (tcp)

TDS (tcp)

TDS (tcp)

Applications use standard SQL client libraries: ODBC, ADO.Net, PHP, …

Load balancer forwards ‘sticky’ sessions to TDS protocol tier

Security Boundary

SQL SQL SQL SQL SQLSQL

GatewayGateway GatewayGateway GatewayGateway GatewayGateway GatewayGateway GatewayGateway

Gateway: TDS protocol gateway, enforces AUTHN/AUTHZ policy; proxy to CloudDB

Scalability and Availability: Fabric, Failover, Replication, and Load balancingScalability and Availability: Fabric, Failover, Replication, and Load balancing

http://ecn.channel9.msdn.com/o9/pdc09/ppt/SVC12.pptx

Topology


and ACID paradigm

Atomicity Transaction as an atomic operation Either all changes are persistently written or none

Consistency Consistent state of database after transaction In case of failure: Full Rollback (atomicity of transaction)

Isolation concurrent transactions not visible to each other Effects of concurrent transactions are the same as running in sequence

Durability transaction results won‘t be lost in case of failure

Table Storage SQL Azure

+ - + -

One query serves max 1000 entities

no limitations

Partition logic included

No app portability App portability Partition logic not included

No relational data store

Relational data store & stored procedures etc.

Table Storage SQL Azure

+ - + -

Scalability out of the box

Every transaction (CRUD) is charged

Transactions within the platform are not charged

No scalability out of the box:hard limit of 50 GB

suited for developing highly scalable, high volume apps

No ACID characteristics

ACID characteristics

More suited for smaller apps (which do not scale)


5 SQL Azure: Table Storage vs. SQL Azure


vs. Table Storage

Azure Tables SQL Azure

DDL REST, LINQ SQL Azure

DML <Key,Value> SQL

Consistency App has to handle this (Timestamp)

ACID

Availability Replication on fault domains

Replication

Partiton-Tolerance Out of the box App has to handle this

Scalability High scale out! App has to handle this


Architecture

Beware of Buzzword

Bingo:=



Availability

Conclusion

degree of detail


Datacenters are located in…


Datacenters are located in…

San AntonioSan AntonioChicagoChicago

ChicagoChicago

DublinDublin

AmsterdamAmsterdam

Hong KongHong Kong

SingaporeSingapore

North American Data CentersNorth American Data Centers European Data CentersEuropean Data Centers Asian Data CentersAsian Data Centers


http://msdn.microsoft.com/en-us/magazine/dd727504.aspx

Roles: Discrete component built with managed code. One instance per VM your app runs in Web- and/or Worker Roles.

Web Role: user interaction (.aspx web pages) in ASP.NET or PHP

Worker Role: Computation (infinity loop, easy to implement) May be written in .NET, Ruby, Java Improve scalability by increasing parallelism and asynchronicity Used for background work

Web Role and Worker Role communicate over messages through Queues


3 Transaction Processing: Web,- and Worker Role


Demo: Developing an app for Azure



Availability

Conclusion

degree of detail


Availability


“Principles of Transaction Processing”, Second Edition p. 23

*min. 2 instances of roles if you want the 99.9% SLA to apply…

Availability: Downtime


Picture: Introducing Windows Azure, v1.2--Chappell.pdf p.22

Availability: Fault Domains

Use 3rd party monitoring provider:http://www.websitepulse.com/

Use our service dashboard:http://www.microsoft.com/windowsazure/

support/status/servicedashboard.aspx


Availability: Monitoring



Availability

Conclusion

degree of detail

Conclusion…



Intr

anet

Inte

rnet

CustomerApplication

Customer

Vendor

IT of your company


InternalWeb Application

Intr

anet

Inte

rnet

CustomerApplication

Customer

Vendor

Internal ProxyHigh level function

AzureCloud app. SQL

Azure

Azure Storage

Cloud app.

Service Bus

NAV

NAVWS

http://www.mygreatwindowsazureidea.com• “I was recently shocked to get my first Azure bill of over $250

for playing around with 3 one-page test sites. […] The dissapointment I encountered when I finally worked out Azure costs a minimum of $1000/year was OVERWHELMING. I'm just SAD, really. Why oh why do MS never think about the small time hobbyist up front?”

• “Among the factors used to calculate the bill is “compute time”. This latter factor, however, has a misleading name: it should be named “instance hosting time” not compute time.”

• “At $0.12/hour per instance, an app using N instances will be billed an average of 24*30*0.12*N/month = ~ $86/month per instance […]”


• http://www.geekzone.co.nz/vs2008/6255 „Getting started with Windows Azure”• http://www.infosysblogs.com/microsoft/2010/03/

azure_table_storage_vs_sql_azu.html „Azure Table Storage Vs. SQL Azure“• http://sqlbits.com/Agenda/event4/

Comparing_Azure_storage_and_SQL_Data_Services/default.aspx „Comparing Azure storage and SQL Data Services”

• http://www.minddriven.de/?p=775 „Will Windows Azure succeed?“• http://msdn.microsoft.com/en-us/library/aa0416cz(VS.80).aspx „Using Optimistic

Concurrency“• http://msdn.microsoft.com/en-us/magazine/dd727504.aspx • „Patterns For High Availability, Scalability, And Computing Power With Windows

Azure”

• Introducing Windows Azure, v1.2--Chappell.pdf• “Principles of Transaction Processing”, Second Edition - Philip A. Bernstein, Eric

Newcomer


8 Sources

Engineering

Azure vs. Google App Engine