This document discusses Microsoft's AppFabric distributed caching technology. It provides an overview of AppFabric, why distributed caching is useful, how to configure AppFabric clients and servers, and how to manage data in an AppFabric cache, including concurrency and high availability. While version 1 has some limitations, it is suitable as a session state provider, and the author expects version 2 to improve the product.

1. 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

2. Agenda
• What is AppFabric?
• Why a Distributed Cache?
• Configuring a client
• Configuring a server
• Managing a cache
• Concurrency
• High availability / load balancing

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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 

11. 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

12. 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

13. 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 

14. Questions?
phil@philippursglove.com
http://philpursglove.blogspot.com
http://www.philippursglove.com/Velocity
http://twitter.com/philpursglove
http://slideshare.net/philpursglove

15. 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

16. 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/