/Raven.Database/Impl/DocumentCacher.cs

using System;

using System.Collections.Specialized;

using System.Runtime.Caching;

using Raven.Abstractions.Data;

using Raven.Abstractions.Extensions;

using Raven.Abstractions.Logging;

using Raven.Database.Config;

using Raven.Json.Linq;



namespace Raven.Database.Impl

{

	public class DocumentCacher : IDocumentCacher

	{

		private readonly InMemoryRavenConfiguration configuration;

		private readonly MemoryCache cachedSerializedDocuments;

		private static readonly ILog log = LogManager.GetCurrentClassLogger();

		

		[ThreadStatic]

		private static bool skipSettingDocumentInCache;



		public DocumentCacher(InMemoryRavenConfiguration configuration)

		{

			this.configuration = configuration;

			cachedSerializedDocuments = new MemoryCache(typeof(DocumentCacher).FullName + ".Cache", new NameValueCollection

			{

				{"physicalMemoryLimitPercentage", configuration.MemoryCacheLimitPercentage.ToString()},

				{"pollingInterval",  configuration.MemoryCacheLimitCheckInterval.ToString(@"hh\:mm\:ss")},

				{"cacheMemoryLimitMegabytes", configuration.MemoryCacheLimitMegabytes.ToString()}

			});

			log.Info(@"MemoryCache Settings:

  PhysicalMemoryLimit = {0}

  CacheMemoryLimit    = {1}

  PollingInterval     = {2}", cachedSerializedDocuments.PhysicalMemoryLimit, cachedSerializedDocuments.CacheMemoryLimit,

			  cachedSerializedDocuments.PollingInterval);

		}



		public static IDisposable SkipSettingDocumentsInDocumentCache()

		{

			var old = skipSettingDocumentInCache;

			skipSettingDocumentInCache = true;



			return new DisposableAction(() => skipSettingDocumentInCache = old);

		}



		public CachedDocument GetCachedDocument(string key, Etag etag)

		{

			CachedDocument cachedDocument;

			try

			{

				cachedDocument = (CachedDocument)cachedSerializedDocuments.Get("Doc/" + key + "/" + etag);

			}

			catch (OverflowException)

			{

				// this is a bug in the framework

				// http://connect.microsoft.com/VisualStudio/feedback/details/735033/memorycache-set-fails-with-overflowexception-exception-when-key-is-u7337-u7f01-u2117-exception-message-negating-the-minimum-value-of-a-twos-complement-number-is-invalid 

				// in this case, we just threat it as uncachable

				return null;

			}

			if (cachedDocument == null)

				return null;

			return new CachedDocument

			{

				Document = (RavenJObject)cachedDocument.Document.CreateSnapshot(),

				Metadata = (RavenJObject)cachedDocument.Metadata.CreateSnapshot(),

				Size = cachedDocument.Size

			};

		}



		public void SetCachedDocument(string key, Etag etag, RavenJObject doc, RavenJObject metadata, int size)

		{

			if (skipSettingDocumentInCache)

				return;



			var documentClone = ((RavenJObject)doc.CloneToken());

			documentClone.EnsureCannotBeChangeAndEnableSnapshotting();

			var metadataClone = ((RavenJObject)metadata.CloneToken());

			metadataClone.EnsureCannotBeChangeAndEnableSnapshotting();

			try

			{

				cachedSerializedDocuments.Set("Doc/" + key + "/" + etag, new CachedDocument

				{

					Document = documentClone,

					Metadata = metadataClone,

					Size = size

				}, new CacheItemPolicy

				{

					SlidingExpiration = configuration.MemoryCacheExpiration,

				});

			}

			catch (OverflowException)

			{

				// this is a bug in the framework

				// http://connect.microsoft.com/VisualStudio/feedback/details/735033/memorycache-set-fails-with-overflowexception-exception-when-key-is-u7337-u7f01-u2117-exception-message-negating-the-minimum-value-of-a-twos-complement-number-is-invalid 

				// in this case, we just threat it as uncachable

			}



		}



		public void RemoveCachedDocument(string key, Etag etag)

		{

			try

			{

				cachedSerializedDocuments.Remove("Doc/" + key + "/" + etag);

			}

			catch (OverflowException)

			{

				// this is a bug in the framework

				// http://connect.microsoft.com/VisualStudio/feedback/details/735033/memorycache-set-fails-with-overflowexception-exception-when-key-is-u7337-u7f01-u2117-exception-message-negating-the-minimum-value-of-a-twos-complement-number-is-invalid 

				// in this case, we just threat it as uncachable

			}

		}



		public void Dispose()

		{

			cachedSerializedDocuments.Dispose();

		}

	}

}