Microsoft ASP.NET: An Microsoft ASP.NET: An Overview of CachingOverview of Caching

Holly MazerolleHolly MazerolleDeveloper Support Engineer Developer Support Engineer Microsoft Developer Support Microsoft Developer Support Microsoft CorporationMicrosoft Corporation

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OverviewOverview

Introduction to ASP.NET cachingIntroduction to ASP.NET caching Output cachingOutput caching Fragment cachingFragment caching Data cachingData caching

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Introduction to Caching in Introduction to Caching in ASP.NETASP.NET

Caching is the most critical factor in creating Caching is the most critical factor in creating scalable, high performance Web applicationsscalable, high performance Web applications

Caching locationsCaching locations Web server, proxy server, and client browsersWeb server, proxy server, and client browsers

Types of cachingTypes of caching Output cachingOutput caching Fragment cachingFragment caching Data cachingData caching

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Output CachingOutput Caching

What is output caching?What is output caching? @ OutputCache directive and the cache @ OutputCache directive and the cache

objectobject Output caching attributes: Output caching attributes:

DurationDuration LocationLocation VaryByParamVaryByParam VaryByHeaderVaryByHeader VaryByCustomVaryByCustom

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What Is Output Caching?What Is Output Caching?

Pages that use the output cache are executed Pages that use the output cache are executed one time, and the page results are cachedone time, and the page results are cached

The pre-executed page is then served to later The pre-executed page is then served to later requestsrequests

Performance and scalability both benefitPerformance and scalability both benefit Server response times reducedServer response times reduced CPU load reducedCPU load reduced

Appropriate caching of pages affects site Appropriate caching of pages affects site performance dramatically performance dramatically

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@ OutputCache Directive and the @ OutputCache Directive and the Cache ObjectCache Object

@ OutputCache declaratively controls @ OutputCache declaratively controls caching behaviorcaching behavior For .aspx, .asmx, or .ascx For .aspx, .asmx, or .ascx

The cache object programmatically controls The cache object programmatically controls caching behaviorcaching behavior

<%@ OutputCache Duration="600“ Location="Any“VaryByParm=“none” %>

Is equivalent to:[C#]Response.Cache.SetExpires(DateTime.Now.AddSeconds(600));Response.Cache.SetCacheability(HttpCacheability.Public);

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OutputCache Members: OutputCache Members: Duration and LocationDuration and Location

Duration sets the time to cache the outputDuration sets the time to cache the output In secondsIn seconds RequiredRequired

Location sets the location to cache the outputLocation sets the location to cache the output ServerServer: The output is held in memory on the Web server : The output is held in memory on the Web server

and is used to satisfy requestsand is used to satisfy requests DownstreamDownstream: A header is added to the response to : A header is added to the response to

indicate to proxy servers to cache the pageindicate to proxy servers to cache the page ClientClient: A header is added to the response indicating to : A header is added to the response indicating to

browsers to cache the pagebrowsers to cache the page AnyAny: Output cache can be located on any of these : Output cache can be located on any of these

locationslocations NoneNone: No output caching is turned on for the item: No output caching is turned on for the item

<%@ OutputCache Duration="600" Location="Any“VaryByParam=“none” %>

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OutputCache Members: OutputCache Members: VaryByParam and VaryByHeaderVaryByParam and VaryByHeader

VaryByParamVaryByParam The cache stores multiple copies of a page based on The cache stores multiple copies of a page based on

specific Querystring or Form parameters and any specific Querystring or Form parameters and any combinations thereofcombinations thereof

VaryByHeaderVaryByHeader The cache stores multiple copies of a page based on The cache stores multiple copies of a page based on

HTTP headersHTTP headers

<%@ OutputCache Duration="10“ VaryByParam="location;count" %>

<%@ OutputCache Duration="60“ VaryByHeader="Accept-Language" %>

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OutputCache Members: OutputCache Members: VaryByCustomVaryByCustom

VaryByCustomVaryByCustom If the value is “Browser,” cache varies by browser type and If the value is “Browser,” cache varies by browser type and

major versionmajor version If the value is a custom string, you must override If the value is a custom string, you must override

HttpApplication.GetVaryByCustomString in the Global.asax HttpApplication.GetVaryByCustomString in the Global.asax and implement your own caching logicand implement your own caching logic

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Fragment CachingFragment Caching

What is fragment caching?What is fragment caching? VaryByControlVaryByControl Nested cached user controlsNested cached user controls Cached controls are not programmableCached controls are not programmable

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What Is Fragment Caching?What Is Fragment Caching?

Just as you can vary the versions of a page Just as you can vary the versions of a page that are output cached, you can output cache that are output cached, you can output cache regions of a pageregions of a page

Regions are defined based on user controlsRegions are defined based on user controls User controls contain their own User controls contain their own

@OutputCache directive@OutputCache directive Fragment caching supportsFragment caching supports

VaryByParamVaryByParam VaryByControlVaryByControl

Location not supported because fragments Location not supported because fragments must reside on server to be assembledmust reside on server to be assembled

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Fragment Caching a User ControlFragment Caching a User Control[*.ascx][*.ascx]

<%@ Language="C#" %> <%@ Language="C#" %>

<%@ OutputCache Duration="10“ <%@ OutputCache Duration="10“ VaryByControl="State;Country" VaryByControl="State;Country"

VaryByParam="*"%> VaryByParam="*"%>

<script runat=server> <script runat=server>

public String State { public String State {

get { return state.Value; } get { return state.Value; }

set { state.Value = State; } } set { state.Value = State; } }

public String Country { public String Country {

get { return country.Value; } get { return country.Value; }

set { country.Value = Country; } } set { country.Value = Country; } }

</script></script>

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VaryByControlVaryByControl

VaryByControlVaryByControl The sixth attribute supported by OutputCacheThe sixth attribute supported by OutputCache Only supported in user control cachingOnly supported in user control caching Caching is based on user control propertiesCaching is based on user control properties

<%@ OutputCache Duration="10“ VaryByControl="State;Country“ VaryByParam="*"%>

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Nested Cached User Controls Nested Cached User Controls

User controls can be nestedUser controls can be nested Cached user controls can also be nestedCached user controls can also be nested Since multiple versions of a user control are Since multiple versions of a user control are

cached, this creates a hierarchy of cached cached, this creates a hierarchy of cached outputoutput

This caching treeThis caching tree Is very efficient and powerfulIs very efficient and powerful Requires almost nothing from a developerRequires almost nothing from a developer

Varying by many properties could create a Varying by many properties could create a large tree, and therefore, a large memory large tree, and therefore, a large memory footprintfootprint

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Cached Controls Are Not Cached Controls Are Not Programmable Programmable Do not try to programmatically access a user Do not try to programmatically access a user

control that is in the cachecontrol that is in the cache Cached controls are not added to the control Cached controls are not added to the control

treetree Trying to access a cached control will throw Trying to access a cached control will throw

an exceptionan exception

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Data CachingData Caching

What is data caching?What is data caching? Working with the cache objectWorking with the cache object Cache dependenciesCache dependencies Scavenging memoryScavenging memory Using callbacks with cachingUsing callbacks with caching

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What Is Data Caching?What Is Data Caching?

The data cache holds application data such The data cache holds application data such as strings, datasets, and other objectsas strings, datasets, and other objects

Adding items to the data cache is easyAdding items to the data cache is easy

Although similar to the familiar application Although similar to the familiar application variables model, it is much more powerfulvariables model, it is much more powerful

Cache (“counter”) = mycount.text

Application(“counter”) = mycount.text

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Working with the Cache ObjectWorking with the Cache Object Cache object featuresCache object features

Dependencies allow logic to invalidate cached Dependencies allow logic to invalidate cached itemsitems

Scavenging (automatic expiration)Scavenging (automatic expiration) Callbacks when an item is removed from cacheCallbacks when an item is removed from cache

To use dependencies or callbacks, use To use dependencies or callbacks, use Cache.Insert or Cache.AddCache.Insert or Cache.Add

Code using cached items must be able to Code using cached items must be able to both create or insert, and retrieve cached both create or insert, and retrieve cached itemsitemsPublic Function GetProductData() As DataSet If (IsNothing(Cache("ProductData")) Then Cache("ProductData") = LoadDataSet()  Return Cache("ProductData")End Function

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Cache DependenciesCache Dependencies

File-based dependenciesFile-based dependencies Cached item invalidated when files changeCached item invalidated when files change

Key-based dependenciesKey-based dependencies Cached item invalided when another cached item Cached item invalided when another cached item

changeschanges

Time-based dependenciesTime-based dependencies Absolute time-based invalidationsAbsolute time-based invalidations Sliding time-based invalidationsSliding time-based invalidations

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Scavenging MemoryScavenging Memory

Automatic system that initiates when memory Automatic system that initiates when memory becomes scarcebecomes scarce

Tag cached items with relative importanceTag cached items with relative importance CacheItemPriority CacheItemPriority CacheItemPriorityDecayCacheItemPriorityDecay

Items must be added to cache using .Add Items must be added to cache using .Add or .Insert to make use of these enumerationsor .Insert to make use of these enumerations

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Using Callbacks with CachingUsing Callbacks with Caching

Create Callbacks with this delegate:Create Callbacks with this delegate:

CacheItemRemovedCallbackCacheItemRemovedCallback Callbacks are used to receive notification Callbacks are used to receive notification

when an item is evicted from the cachewhen an item is evicted from the cache CleanupCleanup UpdateUpdate RecreateRecreate LoggingLogging

Items must be added to caching using .Add Items must be added to caching using .Add or .Insert to use callback functionalityor .Insert to use callback functionality

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ReviewReview

Code that uses items from the data cache Code that uses items from the data cache must be able to create the object, load the must be able to create the object, load the cache, or retrieve the object before using it.cache, or retrieve the object before using it.

Caching can hide problems. Test without Caching can hide problems. Test without caching.caching.

Use tracing, performance counters, and Use tracing, performance counters, and stress software to identify caching wins.stress software to identify caching wins.

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Additional Information about Additional Information about CachingCaching INFO: ASP.NET Caching OverviewINFO: ASP.NET Caching Overview HOW TO: Control Page Output Caching in ASHOW TO: Control Page Output Caching in AS

P.NET by Using Visual Basic .NET P.NET by Using Visual Basic .NET HOW TO: Perform Fragment Caching in ASP.HOW TO: Perform Fragment Caching in ASP.

NET by Using Visual Basic .NET NET by Using Visual Basic .NET

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