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caching-configuration
The document provides instructions on configuring the Metalama caching service, detailing three methods: using custom attributes, using a fabric, and at runtime with caching profiles.

Configuring the caching service

The behavior of the xref:Metalama.Patterns.Caching.Aspects.CacheAttribute aspect can be configured in several ways, including:

  • Expiration (absolute and sliding)
  • Priority
  • Auto-reload
  • Enabled/disabled

These options can be set in three ways:

  • At compile time using the properties of the xref:Metalama.Patterns.Caching.Aspects.CacheAttribute?text=[Cache] or xref:Metalama.Patterns.Caching.Aspects.CachingConfigurationAttribute?text=[CachingConfiguration] attributes
  • At compile time using the xref:Metalama.Patterns.Caching.Aspects.Configuration.CachingConfigurationExtensions.ConfigureCaching* fabric method
  • At run time using the xref:Metalama.Patterns.Caching.CachingProfile class

This article describes these three approaches.

Configuring caching with custom attributes

The xref:Metalama.Patterns.Caching.Aspects.CacheAttribute aspect can be configured by setting the properties of the xref:Metalama.Patterns.Caching.Aspects.CacheAttribute custom attribute. The downside of this approach is that you have to repeat the configuration for each cached method.

To configure several methods with a single line of code, add the xref:Metalama.Patterns.Caching.Aspects.CachingConfigurationAttribute custom attribute to the declaring type, the base type of the declaring type, the enclosing type of the declaring type (if it is nested), or the declaring assembly.

The configuration of Metalama Caching is based on the configuration framework of Metalama Framework. For more details, see xref:fabrics-configuration.

Example: Configuring expiration with custom attributes

In the following example, the absolute expiration of cache items is set to 60 minutes for methods of the PricingService class, but to 20 minutes for the GetProducts method.

[!metalama-file ~/code/Metalama.Documentation.SampleCode.Caching/AbsoluteExpiration_Attribute.cs]

Configuring caching with fabrics

Instead of using custom attributes, you can use a fabric to configure the caching aspect at any level of granularity, thanks to the xref:Metalama.Patterns.Caching.Aspects.Configuration.CachingConfigurationExtensions.ConfigureCaching* fabric extension method.

Example: Configuring expiration with a fabric

The following example sets the absolute expiration to 20 minutes for the namespace MyProduct.MyNamespace.

[!metalama-file ~/code/Metalama.Documentation.SampleCode.Caching/AbsoluteExpiration_Fabric.cs]

Configuring caching at run time with profiles

All compile-time approaches described above have the same drawback: by definition, they cannot be modified at run time. This can be a problem if you want the caching options to be loaded from a configuration file that you can deploy with your application.

Metalama Caching allows you to change caching options at run time with a concept called caching profile. These are sets of options that can be modified at run time and are represented by the xref:Metalama.Patterns.Caching.CachingProfile class.

To modify run-time caching options with a caching profile:

  1. Set the xref:Metalama.Patterns.Caching.Aspects.CachingBaseAttribute.ProfileName property of the xref:Metalama.Patterns.Caching.Aspects.CacheAttribute?text=[Cache] aspect, the xref:Metalama.Patterns.Caching.Aspects.CachingConfigurationAttribute?text=[CachingConfiguration] attribute, or the xref:Metalama.Patterns.Caching.Aspects.Configuration.CachingOptionsBuilder parameter of the xref:Metalama.Patterns.Caching.Aspects.Configuration.CachingConfigurationExtensions.ConfigureCaching* fabric extension method.

    [!NOTE] A default profile is assigned to any cached method even if the xref:Metalama.Patterns.Caching.Aspects.CachingBaseAttribute.ProfileName property is not assigned. This profile can be customized at run time like any other profile.

  2. Go back to the code that initialized the Metalama Caching by calling xref:Metalama.Patterns.Caching.Building.CachingServiceFactory.AddMetalamaCaching*?text=serviceCollection.AddMetalamaCaching or xref:Metalama.Patterns.Caching.CachingService.Create*?text=CachingService.Create, and supply a delegate that calls xref:Metalama.Patterns.Caching.Building.ICachingServiceBuilder.AddProfile*.

Warning

Any configuration property specified through a compile-time mechanism takes precedence over the configuration of the xref:Metalama.Patterns.Caching.CachingProfile.

Example: Configuring expiration with a fabric

In this example, the ProductCatalogue class uses two caching profiles: the default one, and the hot one, which should refresh content more frequently. However, we don't want to hard-code these expiration values in the source code. The following code in Program.cs configures the logging profiles. While the values are hard-coded here, they could easily be read from a configuration file.

[!metalama-test ~/code/Metalama.Documentation.SampleCode.Caching/Profiles/Profiles.cs]