The Need For Speed

A Developer’s Guide to

Distributed Caching with

Velocity AppFabric

Phil Pursglove

phil@philippursglove.com

http://philpursglove.blogspot.com

http://www.philippursglove.com/Velocity

http://twitter.com/philpursglove

http://slideshare.net/philpursglove

Agenda• What is AppFabric?

• Why a Distributed Cache?

• Configuring a client

• Configuring a server

• Managing a cache

• Concurrency

• High availability / load balancing

Caching Review• .NET 1.1

– ASP.NET Cache

• .NET 2.0

– SqlCacheDependency

– Enterprise Library Caching Application Block

• .NET 4.0

– System.Runtime.Caching assembly

– AppFabric

Cache-Aside• The cache-aside pattern

– See if the item you want is in the cache

– If it isn’t (a cache miss),

• Go and get it i.e. from the DB

• Put it in the cache

– If it is,

• Cast it to the desired type and return it

What is AppFabric?

• A combination of two projects:– A distributed cache

• One logical cache shared across a number of physical servers

• Already being used by:– MSDN Forums

– Xbox Live

– MSN

• A session state provider

• In .NET 4.0, a cache provider– A workflow host

• Beta 2 released 1st March 2010– Servers must be .NET 4.0, clients can be .NET 3.5/4.0

Why a Distributed Cache?

• Bigger cache

– Many physical servers contribute to one

logical cache

• High availability

– Multiple servers = fault tolerance

• Increased throughput

– Many servers available to fulfil requests

Terminology

• Cluster

– A number of servers running Velocity

– Not related to Windows clustering

• Cache

– A named cache on a cluster

• Region

– A named part of a cache associated to a

single server

What Data Can I Cache In

AppFabric?

• Any serializable .NET object

– Reference Data (Shared Read)

• e.g. Product categories

– Activity Data (Exclusive Write)

• e.g. Shopping Basket

– Resource Data (Read and Write)

• e.g. product stock data

Configuring the AppFabric

Client• Two assembly references to add:

– Microsoft.ApplicationServer.Caching.Client.dll

– Microsoft.ApplicationServer.Caching.Core.dll

• Cache hosts can be hard-coded or in

web.config/app.config

• Clients

– Routing vs Simple

– Local caches

Using AppFabric

• Add/Remove

• Concurrency– Optimistic

– Pessimistic

• Regions– Live inside a cache

– Tie a group of cached objects to a specific node

– But adds extra options (Tags) for retrieving the object

Configuring an AppFabric

Server• Cluster configuration can be held:

– On a network share (XML Provider)

– In a SQL Server DB (SQL Provider)

• Integrated Security only

– AppFabric servers must be inside a

domain

Managing An AppFabric

Cluster• Powershell integration

– Can start/stop a whole cluster or

individual servers

– Create new named caches

• But not regions

– Get cache statistics

• MDCAdmin tool

– WPF app sitting on top of Powershell

Summary

• Velocity is going to be great

… in v2

• v1 is worth looking at as a session

state provider

– The end of sticky load-balancing

Questions?

phil@philippursglove.com

http://philpursglove.blogspot.com

http://www.philippursglove.com/Velocity

http://twitter.com/philpursglove

http://slideshare.net/philpursglove

References• Documentation on MSDN

– http://tinyurl.com/msdnappfabric

• Velocity team blog – http://blogs.msdn.com/velocity

• AppFabric blog for IT Pros– http://blogs.technet.com/appfabric/

• TechEd videos– http://tinyurl.com/velocityteched

• Mix 09 video– http://tinyurl.com/velocitymixvideo

• Mix 10 video– http://tinyurl.com/velocitymix10video

• ARCCast Video– http://tinyurl.com/velocityscotthavideo

• ScottHa on Velocity– http://tinyurl.com/velocityhanselminutes

References• AppFabric coverage on StackOverflow

– http://tinyurl.com/stackoverflowvelocity– http://tinyurl.com/stackoverflowappfabric

• DotNetRocks– http://tinyurl.com/dotnetrocksappfabric

• Other .NET distributed caches– NCache - http://tinyurl.com/ncache– Memcached - http://tinyurl.com/smoe– Oracle Coherence – http://tinyurl.com/oraclecoherence– SharedCache – http://codeplex.com/sharedcache

• Extensions Project– http://tinyurl.com/mscacheext

• Admin Tool– http://mdcadmintool.codeplex.com/