As caching is an essential technology in the development of high-performance web services, Service Stack has a number of different caching options available that each share the same common client interface (ICacheClient) for the following cache providers:

• Redis - A very fast key-value store that has non-volatile persistent storage and support for rich data structures such as lists and sets.
• OrmLiteCacheClient - Supports all OrmLite's RDBMS providers for using an existing RDBMS as a distributed cache.
• Memcached - The tried and tested most widely used cache provider.
• In Memory Cache - Useful for single host web services and enabling unit tests to run without needing access to a cache server.
• Aws DynamoDB Cache Client - For using with Amazon's Dynamo DB backend hosted on Amazon Web Services
• Azure Cache Client - For using the Azure DataCache client when your application is hosted on Azure.

To configure which cache should be used, the particular client has to be registered in the IoC container:

container.Register<ICacheClient>(new MemoryCacheClient());

container.Register<IRedisClientsManager>(c => 
    new PooledRedisClientManager("localhost:6379"));

container.Register(c => c.Resolve<IRedisClientsManager>().GetCacheClient());

//Register OrmLite Db Factory if not already
container.Register<IDbConnectionFactory>(c => 
    new OrmLiteConnectionFactory(connString, SqlServerDialect.Provider)); 

container.RegisterAs<OrmLiteCacheClient, ICacheClient>();

//Create 'CacheEntry' RDBMS table if it doesn't exist already
container.Resolve<ICacheClient>().InitSchema(); 

container.Register<ICacheClient>(
    new MemcachedClientCache(new[] { "127.0.0.0" }); //Add Memcached hosts

var awsDb = new AmazonDynamoDBClient(
    AWS_ACCESS_KEY, AWS_SECRET_KEY, RegionEndpoint.USEast1);
var cache = new DynamoDbCacheClient(new PocoDynamo(awsDb));
cache.InitSchema();

container.Register<ICacheClient>(
    new AzureCacheClient("MyAppCache")); //Add your Azure CacheName if any

To cache a response you simply have to call ToOptimizedResultUsingCache which is an extension method existing in ServiceStack.ServiceHost.

In your service:

public class OrdersService : Service
{
    public object Get(CachedOrders request)
    {
        var cacheKey = "unique_key_for_this_request";
        return base.Request.ToOptimizedResultUsingCache(base.Cache,cacheKey,()=> 
            {
                //Delegate is executed if item doesn't exist in cache 
                //Any response DTO returned here will be cached automatically
            });
    }
}

Tip: There exists a class named UrnId which provides helper methods to create unique keys for an object.

ToOptimizedResultUsingCache also has an overload which provides a parameter to set the timespan when the cache should be deleted (marked as expired). If now a client calls the same service method a second time and the cache expired, the provided delegate, which returns the response DTO, will be executed a second time.

var cacheKey = "some_unique_key";
//Cache should be deleted in 1h
var expireInTimespan = new TimeSpan(1, 0, 0);
return base.Request.ToOptimizedResultUsingCache(
    base.Cache, cacheKey, expireInTimespan, ...)

If now for example an order gets updated and the order was cached before the update, the webservice will still return the same result, because the cache doesn't know that the order has been updated.

So there are two options:

• Use time based caching (and expire cache earlier)
• Cache on validility

When the cache is based on validility the caches are invalidated manually (e.g. when a user modified his profile, > clear his cache) which means you always get the latest version and you never need to hit the database again to rehydrate the cache if it hasn't changed, which will save resources.

So if the order gets updated, you should delete the cache manually:

public class CachedOrdersService : Service
{
    public object Put(CachedOrders request)
    {
        //The order gets updated...
        var cacheKey = "some_unique_key_for_order";
        return base.Request.RemoveFromCache(base.Cache, cacheKey);
    }
}

If now the client calls the webservice to request the order, he'll get the latest version.

As it sometimes beneficial to have access to a local in-memory Cache in addition to your registered ICacheClient Caching Provider we also pre-register a MemoryCacheClient that all your Services now have access to from the LocalCache property, i.e:

    MemoryCacheClient LocalCache { get; }

This doesn't affect any existing functionality that utilizes a cache like Sessions which continue to use your registered ICacheClient, but it does let you change which cache you want different responses to use, e.g:

var cacheKey = "unique_key_for_this_request";
return base.Request.ToOptimizedResultUsingCache(LocalCache, cacheKey, () => {
    //Delegate is executed if item doesn't exist in cache 
});

If you don't register a ICacheClient ServiceStack automatically registers a MemoryCacheClient for you which will also refer to the same instance registered for LocalCache.

The ICacheClientExtended API is used to to provide additional non-core functionality to our most popular Caching providers:

• Redis
• OrmLite RDBMS
• In Memory
• AWS

The new API's are added as Extension methods on ICacheClient so they're easily accessible without casting, the new API's available include:

• GetKeysByPattern(pattern) - return keys matching a wildcard pattern
• GetAllKeys() - return all keys in the caching provider
• GetKeysStartingWith() - Streaming API to return all keys Starting with a prefix

With these new API's you can now easily get all active User Sessions using any of the supported Caching providers above with:

var sessionPattern = IdUtils.CreateUrn<IAuthSession>(""); //= urn:iauthsession:
var sessionKeys = Cache.GetKeysStartingWith(sessionPattern).ToList();

var allSessions = Cache.GetAll<IAuthSession>(sessionKeys);

A live demo of the ICacheClient is available in The ServiceStack.Northwind's example project. Here are some requests to cached services:

• /customers
• /customers/ALFKI
• /customers/ALFKI/orders

Which are simply existing web services wrapped using ICacheClient that are contained in CachedServices.cs