The ServiceStack Routed Cache Client is an ICacheClient implementation (ICacheClientExtended to be more exact) that acts as a facade to a collection of multiple other cache clients. It has minimum overhead and does not store cache values itself, but only routes various cache operations (read, write, flush, remove etc.) to a specific registered client, based on an associated rule (for instance, whether the key starts with a given string).

The main issue for me was (and possibly many others) that I could not register a different cache client for session storage (say, OrmLiteCacheClient), whilst continuing to make use of the standard MemoryCacheClient .

Available as a NuGet package, here.

Install-Package LVD.ServiceStack.RoutedCacheClient -Version 1.1.0

dotnet add package LVD.ServiceStack.RoutedCacheClient --version 1.1.0

using LVD.ServiceStackRoutedCacheClient.

In this example, the default MemoryCacheClient provided by ServiceStack is used as a fallback client, which means it will used to handle keys that are not matched by any of the registered rules.

IRoutedCacheClient routedCacheClient = new DefaultRoutedCacheClient(new MemoryCacheClient());

For example, registering a ServiceStack OrmLite cache client for ServiceStack sessions:

OrmLiteCacheClient<CacheEntry> ormLiteCacheClient =
    new OrmLiteCacheClient<CacheEntry>();

routedCacheClient.PushClientWithRule(new KeyStartsWithStringCacheClientRule(ormLiteCacheClient,
    StringComparison.InvariantCultureIgnoreCase,
    "urn:iauthsession:",
    "sess:"));

Or simpler, using PushServiceStackSessionCacheClient(), which automatically registers your provided cache client with a KeyStartsWithStringCacheClientRule and the above prefixes: urn:iauthsession: and sess:.

OrmLiteCacheClient<CacheEntry> ormLiteCacheClient =
    new OrmLiteCacheClient<CacheEntry>();

routedCacheClient.PushServiceStackSessionCacheClient(ormLiteCacheClient);

The library provides the following built-in conditions:

• KeyStartsWithStringCacheClientRuleCondition - matches keys that start with a given sub-string;
• KeyEndsWithStringCacheClientRuleCondition - matches keys that end with a given sub-string;
• KeyMatchesRegexpCacheClientRuleCondition - matches keys based on a regular expression;
• ServiceStackSessionKeyCacheClientRuleCondition - matches keys used to store ServiceStack session data;
• AlwaysTrueCacheClientRuleCondition - matches any key;
• AlwaysFalseCacheClientRuleCondition - doesn't match anything;
• MatchAnyRuleCondition - allows composing conditions using OR boolean operator (i.e. returns true if at least one condition evaluates to true);
• MatchAllRuleCondition - allows composing conditions using AND boolean operator (i.e. returns true if all conditions evaluate to true).

The library provides the following built-in rules:

• GenericConditionBasedCacheClientRule - matches keys that satisfy a given condition;
• KeyStartsWithStringCacheClientRule - matches keys that start with a given sub-string (uses KeyStartsWithStringCacheClientRuleCondition);
• KeyEndsWithStringCacheClientRule - matches keys that end with a given sub-string (uses KeyEndsWithStringCacheClientRuleCondition);
• KeyMatchesRegexpCacheClientRule - matches keys based on a regular expression (uses KeyMatchesRegexpCacheClientRuleCondition);
• ServiceStackSessionKeyCacheClientRule - matches keys used to store ServiceStack session data (uses ServiceStackSessionKeyCacheClientRuleCondition);
• AlwaysTrueCacheClientRule - matches any key (uses AlwaysTrueCacheClientRuleCondition);
• AlwaysFalseCacheClientRule - doesn't match anything (uses AlwaysFalseCacheClientRuleCondition).

Creating your own conditions is as easy as implementing IRoutedCacheClientRuleCondition with the single method bool Matches ( string key ). This is also the recommended way of exteding the library's routing behaviour.

As an example, here is the implementation of the built-in KeyStartsWithStringCacheClientRuleCondition condition:

public class KeyStartsWithStringCacheClientRuleCondition : IRoutedCacheClientRuleCondition
{
	private List<string> mTokens = new List<string>();

	private StringComparison mStringComparisonMode;

	public KeyStartsWithStringCacheClientRuleCondition ( StringComparison stringComparisonMode,
		params string[] tokens )
	{
		if ( tokens == null || tokens.Length == 0 )
			throw new ArgumentNullException( nameof( tokens ) );

		mTokens.AddRange( tokens );
		mStringComparisonMode = stringComparisonMode;
	}

	public bool Matches ( string key )
	{
		if ( string.IsNullOrWhiteSpace( key ) )
			throw new ArgumentNullException( nameof( key ) );

		foreach ( string token in mTokens )
			if ( key.StartsWith( token, mStringComparisonMode ) )
				return true;

		return false;
	}

	public StringComparison StringComparisonMode 
		=> mStringComparisonMode;
}

Creating your own rules is as easy as - extending the GenericConditionBasedCacheClientRule class and providing a condition to this base class (this is a useful shortcut to always instantiating GenericConditionBasedCacheClientRule with the same condition). - or extending the BaseCacheClientRule class and providing an implementation for the bool Matches ( string key ) method (should you wish to bypass using a condition altogether).

Example #1 - the implementation of the built-in KeyStartsWithStringCacheClientRule rule:

public class KeyStartsWithStringCacheClientRule : GenericConditionBasedCacheClientRule
{
	public KeyStartsWithStringCacheClientRule ( ICacheClient cacheClient,
		KeyStartsWithStringCacheClientRuleCondition condition )
		: base( cacheClient, condition )
	{
		return;
	}

	public KeyStartsWithStringCacheClientRule ( ICacheClient cacheClient,
		StringComparison stringComparisonMode,
		params string[] tokens )
		: this( cacheClient, new KeyStartsWithStringCacheClientRuleCondition( stringComparisonMode, tokens ) )
	{
		return;
	}
}

Example #2 - the implementation of the built-in GenericConditionBasedCacheClientRule rule:

public class GenericConditionBasedCacheClientRule : BaseCacheClientRule
{
	private IRoutedCacheClientRuleCondition mCondition;

	public GenericConditionBasedCacheClientRule ( ICacheClient cacheClient, IRoutedCacheClientRuleCondition condition )
		: base( cacheClient )
	{
		mCondition = condition
			?? throw new ArgumentNullException( nameof( condition ) );
	}

	public override bool Matches ( string key )
	{
		if ( string.IsNullOrWhiteSpace( key ) )
			throw new ArgumentNullException( nameof( key ) );

		return mCondition.Matches( key );
	}

	private IRoutedCacheClientRuleCondition Condition 
		=> mCondition;
}

The dispose behaviour of the DefaultRoutedCacheClient, before version 1.1.0 was:

• to automatically dispose all the registered cache clients by default (this could not be altered);
• to no throw ObjectDisposedException when invoking methods on diposed instances.

After 1.1.0, the behaviour is as follows:

• to automatically dispose all the registered cache clients by default (this can now be configured);
• to throw throw ObjectDisposedException when invoking methods on diposed instances.

To change how DefaultRoutedCacheClient handles various registered cache clients you may:

• use DefaultRoutedCacheClient ( ICacheClient fallbackClient, bool autoDispose ) constructor to set whether or not the fallback cache client should be disposed along with the DefaultRoutedCacheClient it is registered with;
• use IRoutedCacheClientRule.AutoDispose property to set whether the cache client associated with a rule should be disposed along with the DefaultRoutedCacheClient it is registered with.

A sample project has been provided, to see just how this would behave in the real world.
Head over to LVD.ServiceStack.RoutedCacheClient.Example for the full details, but, in short, it exposes three service endpoints:

• /set-cache-randomly - set some cache values using the Service.Cache instance;
• /set-session-randomly - set some session values using the Service.SessionBag instance;
• /list-cache-providers-data - list all values for each of the cache providers.

The output of /list-cache-providers-data looks something like:

{
    "cacheProvidersData": {
        "fallbackCacheClient": {
            "SampleCacheClientService.randomText": "ef42894b-fbb6-4971-b983-0aea9e88f10a",
            "SampleCacheClientService2020-04-06 10:51.hitCountsPerMinute": "12",
            "SampleCacheClientService2020-04-06 10:52.hitCountsPerMinute": "4"
        },
        "sessionCacheClient": {
            "sess:vKQ8aph3Xdp1ro9YqBzK:SampleCacheClientService.sessionRandomText": "e2f581da-ad0c-4896-8b4f-b3646f79bc7e",
            "sess:vKQ8aph3Xdp1ro9YqBzK:SampleCacheClientService.hitCountsPerSession": "12"
        }
    }
}

• KeyStartsWithStringCacheClientRule no longer extends BaseCacheClientRule, but GenericConditionBasedCacheClientRule;
• ServiceStackSessionKeyCacheClientRule no longer extends BaseCacheClientRule, but GenericConditionBasedCacheClientRule;
• AlwaysTrueCacheClientRule no longer extends BaseCacheClientRule, but GenericConditionBasedCacheClientRule;
• AlwaysTrueCacheClientRule now throws an exception when checking for an empty key (calling .Matches(null|string.Empty));
• Calling any method on a disposed DefaultRoutedCacheClient instance throws ObjectDisposedException.

• Added utility methods to inspect cache client configuration - Issue #4;
• Refactoring - extracted the explicit concept of condition from that of a cache client rule - Issue #2;
• Additional conditions provided:
  • cache key ends with substring - Issue #5;
  • cache key matches a given regexp - Issue #6;
  • compose conditions using OR operator;
  • compose conditions using AND operator.
• Improved test coverage and code comments.

Initial release.

As a rough timeline, I would like to see the following happening:

• Refactor things a bit and add some comments, at least for critical areas;
• Add some more routing rules. Here are some of the rules I'm thinking about:
  • match a regex pattern;
  • match rules that ends with a given string;
  • composed rules using basic AND/OR logical operators.
• Enhance the API:
  • would be useful to have a way of listing all the registered cache clients;
  • allow method chaining when registering cache client rules.
• Additional automated tests (in-progress).

I put some of my free time into developing and maintaining this plugin. If helped you in your projects and you are happy with it, you can...