INDIA September 2011 virtual techdays

(1)

virtual techdays

INDIA

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28-30 September 2011

Building highly Available Services on Windows Azure Platform

Pooja Singh

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Technical Architect, Accenture

Aakash Sharma

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Technical Lead, Accenture

Laxmikant Bhole

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Senior Architect, Accenture

(2)



You know the basics of

 Web/Worker roles

 SQL Azure

 Windows Azure Storage

 Windows Azure Diagnostics

virtual techdays

INDIA

_│

28-30 September 2011

Assumptions

(3)



Topics

 Understand Availability

 Causes for unavailability

 What you get with Azure

 What you do on your own

 Guiding Principles



Audience

 Developers & Architects community

 People with high available services needs



Takeaway

 Windows Azure inherent attributes for building highly available services

 Architectural expectations for building highly available services

virtual techdays

INDIA

_│

28-30 September 2011

S E S S I O N A G E N D A

(4)

virtual techdays

INDIA

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28-30 September 2011

How do “you” define “Availability”

• What is acceptable Downtime

• What happens in case of failure

– All functionality required to be available? – Degraded functionality to be available – Failsafe

(5)

virtual techdays

INDIA

_│

28-30 September 2011

Cost of building highly available services

• Unavailability Vs High Availability

Availability Cost &

(6)

virtual techdays

INDIA

_│

28-30 September 2011

Implementation costs for a new project

Implementation cost for a startup company that offers its software as a service with a hosting company.

6

Traditional

(7)

virtual techdays

INDIA

_│

28-30 September 2011

Causes for unavailability

• Increase in workload

– Non-scalable architecture – Poor performance

• Platform Failures

• Upgrades

• Failure

– Hardware – Network – Transient conditions

(8)

virtual techdays

INDIA

_│

28-30 September 2011

(9)

virtual techdays

INDIA

_│

28-30 September 2011

Azure to “rescue”

(10)

virtual techdays

INDIA

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28-30 September 2011

(11)

virtual techdays

INDIA

_│

28-30 September 2011

Azure out-of-box features

• Elasticity

– Scale up/down compute resources on-demand

• Self Service Management

– Self recovery for nodes

• Fault Domains

• Storage Resilience

– 3 copies of storage – Geo Replication

(12)

virtual techdays

INDIA

_│

28-30 September 2011

(13)

virtual techdays

INDIA

_│

28-30 September 2011

Design for Increased Load

(14)

virtual techdays

INDIA

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28-30 September 2011

Is this Scalable?

Web Role Instance 1 Web Role Instance 2 Web Role Instance 3 Web Role Instance 4 SQL Azure Load B alan cer

(15)

virtual techdays

INDIA

_│

28-30 September 2011

Is this Scalable?

Web Role Instance 1 Web Role Instance 2 Worker Role

Instance 1 _{Worker Role} Instance 2 SQL Azure Load B alan cer Table storage Blob storage Queue

(16)

virtual techdays

INDIA

_│

28-30 September 2011

Design for Scalability

• Use loosely coupled nodes

• Design for redundancy

• Scale “OUT” everything

– Better to have 50 one GB databases than one 50 GB database

(17)

virtual techdays

INDIA

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28-30 September 2011

Design for Performance

• Service and data closer to user

– Same data center to avoid network latency – CDN

– Caching

• Be mindful of the throughput and transaction thresholds

• Auto-scaling

(18)

virtual techdays

INDIA

_│

28-30 September 2011

How “CDN” works

• Contents closer to end-users

• 24 physical nodes globally

• CDN works for web apps & public blobs

Azure Storage CDN – Region A CDN – Region B Copy of Blob A Copy of Blob A Blob A Users in Europe Users in Asia

(19)

virtual techdays

INDIA

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28-30 September 2011

Decide Upgrade Strategies

(20)

virtual techdays

INDIA

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28-30 September 2011

Upgrade Strategies

• VIP Swap

• New Service and DNS swap

• Upgrade Domains

(21)

virtual techdays

INDIA

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28-30 September 2011

How does upgrade domain work?

Load Balancer DNS Myservice.Cloudapp.net Myservice v1 Myservice v1 Myservice v1 Myservice v2 Myservice v2 Myservice v2

(22)

virtual techdays

INDIA

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28-30 September 2011

Handle Failure

(23)

virtual techdays

INDIA

_│

28-30 September 2011

Fault Tolerance

• Self recovery

– Can your Service fix itself?

• Transaction & Recovery

– Loosely coupled

– Transaction rollback and recovery

• Network Failures

(24)

virtual techdays

INDIA

_│

28-30 September 2011

What is “Retry” logic?

• When - Network failure or transient conditions

– Service is temporarily unavailable E.g. SQL Azure Error 40501

The service is currently busy. Retry request after 10 seconds.

• What - Retry for any external connections

– SQL Azure

– Windows Azure Storage – Service Bus

– Any external service

• How - Use RetryPolicy class or Transient Fault Handling Framework

– NoRetry – Retry

(25)

virtual techdays

INDIA

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28-30 September 2011

“Retry” Code Example

(26)

virtual techdays

INDIA

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28-30 September 2011

Disaster Recovery

(27)

virtual techdays

INDIA

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28-30 September 2011

Disaster Recovery

• Backups

– Fault Domain – Geo-replication

• Traffic Manager

– Performance – Round Robin – Failover

(28)

virtual techdays

INDIA

_│

28-30 September 2011

How “Traffic Manager” works

• Policies

– Performance

• Use when geo-distributed services

– Round Robin

• Large user base

– Failover

• Small user base

(29)

virtual techdays

INDIA

_│

28-30 September 2011

Traffic Manager – Performance Policy

East Asia DC Myservice-ea.cloudapp.net

Myservice

North Europe DC Myservice-ne.cloudapp.net

Myservice

North Central U.S. DC Myservice-ncus.cloudapp.net

Myservice DNS

myservice.com

Decide which data center to connect Traffic Manager

(30)

virtual techdays

INDIA

_│

28-30 September 2011

Load Test, Diagnostics & Monitoring

• Load test your service

– Visual Studio 2010 Ultimate Load Tests

• Diagnostics

– Windows Azure Diagnostics – Service Management APIs – Storage Management APIs – CSS SQL Azure Diagnostics