Windows Azure Caching: Difference between revisions

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'''Windows Azure Caching''' is an in-memory, [[Distributed cache|distributed caching]] feature designed for [[WindowsMicrosoft Azure]] applications.<ref name=CachingMain>{{cite web|title=Caching inwas available as a part of the Windows Azure|url=http://msdn SDK.microsoft.com/en-us/library/gg278356.aspx|work=MSDN Library|publisher=Microsoft|accessdate=12The FebruaryAzure 2013}}</ref>Managed CachingCache isand availableIn-Role asCache aservices partwere ofretired, theand WindowsMicrosoft recommended migration to Azure SDKRedis Cache.

==Architecture==

Windows Azure Caching allows a cloud service to host Caching on a Windows Azure role.<ref name="CachingMain">{{cite web |title=Caching in Windows Azure |url=http://msdn.microsoft.com/en-us/library/gg278356.aspx |accessdate=12 February 2013 |work=MSDN Library |publisher=Microsoft}}</ref> The cache is distributed across all running instances of that role. Therefore, the amount of available memory in the cache is determined by the number of running instances of the role that hosts Caching and the amount of physical memory reserved for Caching on each instance.<ref name=CachingCapacityPlanning>{{cite web|title=Capacity Planning Considerations for Windows Azure Caching|url=http://msdn.microsoft.com/en-us/library/hh914129.aspx|work=MSDN Library|publisher=Microsoft|accessdate=13 February 2013}}</ref>

There are two deployment topologies for Caching:

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The following diagram shows Caching in a dedicated topology. The cloud service shown has three roles: Web1, Worker1, and Cache1. There are two running instances of each role. In this example, the cache is distributed across all instances of the dedicated Cache1 role.

[[File:Windows Azure Caching (Dedicated).jpg|Type=frame|Location=none|300px|Represents a running Windows Azure cloud service that uses Caching with a dedicated topology.]]

A dedicated topology has the advantage of scaling the caching tier independently of any other role in the cloud service.<ref name=CachingCacheCluster>{{cite web|title=About Windows Azure Caching, Cache Cluster|url=http://msdn.microsoft.com/en-us/library/hh914161.aspx#Concept_CacheClusters|work=MSDN Library|publisher=Microsoft|accessdate=13 February 2013}}</ref> For the best Caching performance, a dedicated topology is recommended because the role instances do not share their resources with other application code and services.<ref name=CachingDedicated/>

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The following diagram shows Caching in a co-located topology. The cloud service has two roles: Web1 and Worker1. There are two running instances of each role. In this example, the cache is distributed across all instances of the Web1 role. Because this role also hosts the web front-end for the cloud service, the cache is configured to use only a percentage of the physical memory on each instance of the Web1 role.

[[File:Windows Azure Caching (Co-located).jpg|Type=frame|Location=none|250px|Represents a running Windows Azure cloud service that uses Caching with a co-located topology.]]

A co-located cache is a cost-effective way to make use of existing memory on a role within a cloud service.<ref name=CachingColocated/>

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When hosting Caching on roles, the '''DataCache''' class constructor can be used to specify both the named cache and the '''dataCacheClient''' section for the cache client settings. The following code shows how to create a named cache, ''NamedCache2'', using the settings from a '''dataCacheClient''' section named ''customClient''.

<syntaxhighlight lang=CSharp"csharp">

DataCachevar Cachecache = new DataCache("NamedCache2", "customClient");

</syntaxhighlight>

The following method shows how to use the ''Cache'' object to retrieve data from the cache. In this example, a user identifier (''userid'') is the key for the associated user information object. The code first attempts to get this user information from the cache using the ''userid'' key. If that does not succeed, the code retrieves the information with a database query and then stores the returned user data in the cache. The next time the same code is run, the user information will be returned from the cache rather than the database. This assumes that the cached data has not been expired or evicted.

<syntaxhighlight lang=CSharp"csharp">

dataType GetUserData(string useriduserId)

{

dataType data = null;

// Attempt to retrieve the user data from the cache:

object dataObject = Cache.Get(useriduserId);

if (dataObject != null)

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{

// If it doesn't exist in the cache, retrieve it from the database:

data = GetUserDataFromDatabase("SELECT * FROM users WHERE useriduserId = @useriduserId", useriduserId);

// Put the returned data in the cache for future requests:

Cache.Add(useriduserId, data);

}

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The following method shows how to update data that is already in the cache.

<syntaxhighlight lang=CSharp"csharp">

void UpdateUserData(string useriduserId, dataType data)

{

// Update the user information in the database:

result = UpdateUserDataInDatabase(useriduserId, data);

if (result)

{

// If successfully updated, update the cache:

Cache.Put(useriduserId, data);

}

}

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The following call removes the item from the cache.

<syntaxhighlight lang=CSharp"csharp">

Cache.Remove(useriduserId);

</syntaxhighlight>

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==History==

Windows Azure Caching has its roots in an on-premises technology, [[AppFabric]]. It was originally released as one of several Windows Azure AppFabric services, but the AppFabric designation in Windows Azure has since been abandoned. Many of the assembly names, namespaces, and APIs are identical between Windows Azure Caching and AppFabric Caching.<ref name=CachingOnPremisesAndCloud>{{cite web|title=Differences Between Caching On-Premises and in the Cloud|url=http://msdn.microsoft.com/en-us/library/gg185678.aspx|work=MSDN Library|publisher=Microsoft|accessdate=13 February 2013}}</ref> The first release of Caching for Windows Azure in April 2011 provided caching as a managed service in Windows Azure.<ref name=Caching2011Release>{{cite web|title=Introducing the Windows Azure Caching Service|url=http://msdn.microsoft.com/en-us/magazine/gg983488.aspx|work=MSDN Magazine|publisher=Microsoft|accessdate=13 February 2013}}</ref> This offering is now called Shared Caching.

In October 2012, support was added for hosting Caching on roles within a cloud service deployment.<ref name=CachingRelNotes>{{cite web|title=Windows Azure Caching Release Notes (October 2012)|url=http://msdn.microsoft.com/library/jj651667.aspx|work=MSDN Library|publisher=Microsoft|accessdate=13 February 2013}}</ref> This is now called WindowWindows Azure Caching.

==Related caching technologies==

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! Caching Technology !! Target !! Installed By !! Description

|-

| [[AppFabric Caching Service|AppFabric Caching]] || [[On-premises software|On-Premises]] || [[AppFabric]] || Distributed on-premises cache that uses servers that the user provisions and manages.

|-

| [[Windows Azure Caching#Architecture|Windows Azure Caching]] || [[Cloud computing|Cloud]] || [http://www.windowsazure.com/en-us/develop/net/#/ Windows Azure SDK] || Caching is distributed across the instances of a single role in a Windows Azure cloud service deployment.

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* [http://msdn.microsoft.com/en-us/library/jj189876.aspx Windows Azure Caching Samples]

* [http://msdn.microsoft.com/en-us/library/windowsazure/microsoft.applicationserver.caching Windows Azure Caching Class Library Reference]

{{Microsoft Azure Services Platform}}

[[Category:Microsoft cloud services]]