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CLOUDS, GUIDs and HOUNDS

Josh TwistPrincipal ADM

Premier Support for Developers (PSfD)Microsoft UK

www.thejoyofcode.com@joshtwist

jtwist@microsoft.com

The Scenario

Predictable Bursting

High level stuff you already know

Web Roles Worker Roles

Table Storage Blob Storage SQL Azure

The Architecture

Push

LOTS of

users

Problem 1: Seriously? A guid?

Internet Explorer 9

Possible Solutions

Use SQL Azure

Create a global counter

Configure Partitions0-

1,000,000

1,000,001 -

2,000,000

2,000,001 -

3,000,000

The problem(s) with configuration

X

XX

Our Solution

R = 1,000

R = 1,000

Write back new max identifier where eTag is

the same.

Request current max identifier

3,000

eTag = XCV243987243KD

Nice!

• Rate of requests to storage = Rate of requests / R(not related to the number of nodes)

• Entirely self managing• Produces relatively sequential

identifiers• Incredibly fast• Configuration can be modified at

runtime if necessary

Problem 2: Release the Hounds!

Solution 1: Polling

Poll

Poll

Poll

Unleash!

Go!

Polling Approach

Pros Cons

Easy Peasy Polling always feels a bit… ‘naff’?

Cheap Inherent latency (up to T)

Solution 2: Listening

Connect

Connect

Connect

Unleash!

Unleash!

Unleash!

Unleash!

Listening Approach

Pros Cons

Direct! Feels good.

Costs money to open connections from your ‘n’ nodes

No Latency? Actual Latency

No state. A freshly provisioned node could miss the ‘unleash’ signal.

Thanks!

This story will feature in November’s MSDN magazine

www.thejoyofcode.com@joshtwist

jtwist@microsoft.com

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