Persistant cache abstraction and runtime loading

1 files changed, 242 insertions, 0 deletions

diff --git a/plugins/ObjectCacheServer/src/Endpoints/CacheSystemUtil.cs b/plugins/ObjectCacheServer/src/Endpoints/CacheSystemUtil.cs
new file mode 100644
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+++ b/plugins/ObjectCacheServer/src/Endpoints/CacheSystemUtil.cs
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+/*
+* Copyright (c) 2023 Vaughn Nugent
+* 
+* Library: VNLib
+* Package: ObjectCacheServer
+* File: CacheSystemUtil.cs 
+*
+* CacheSystemUtil.cs is part of ObjectCacheServer which is part of the larger 
+* VNLib collection of libraries and utilities.
+*
+* ObjectCacheServer is free software: you can redistribute it and/or modify 
+* it under the terms of the GNU Affero General Public License as 
+* published by the Free Software Foundation, either version 3 of the
+* License, or (at your option) any later version.
+*
+* ObjectCacheServer is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU Affero General Public License for more details.
+*
+* You should have received a copy of the GNU Affero General Public License
+* along with this program.  If not, see https://www.gnu.org/licenses/.
+*/
+
+using System;
+using System.IO;
+using System.Text.Json;
+using System.Collections;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+using VNLib.Plugins;
+using VNLib.Utils.Memory;
+using VNLib.Plugins.Extensions.Loading;
+
+namespace VNLib.Data.Caching.ObjectCache.Server
+{
+    internal static class CacheSystemUtil
+    {
+        const string PERSISTANT_ASM_CONFIF_KEY = "persistant_cache_asm";
+        const string USER_CACHE_ASM_CONFIG_KEY = "custom_cache_impl_asm";
+        const string LOAD_METHOD_NAME = "OnRuntimeLoad";
+        const string TEARDOWN_METHOD_NAME = "OnSystemDetach";
+
+        /// <summary>
+        /// Loads the <see cref="IBlobCacheTable"/> implementation (dynamic or default) into the process
+        /// and initializes it and it's backing store.
+        /// </summary>
+        /// <param name="plugin"></param>
+        /// <param name="config">The configuration object that contains loading variables</param>
+        /// <param name="heap">The heap for memory cache table to allocate buffers from</param>
+        /// <param name="cacheConf">The cache configuration object</param>
+        /// <returns>The loaded <see cref="IBlobCacheTable"/> implementation</returns>
+        /// <exception cref="FileNotFoundException"></exception>
+        public static IBlobCacheTable LoadMemoryCacheSystem(this PluginBase plugin, IConfigScope config, IUnmangedHeap heap, CacheConfiguration cacheConf)
+        {
+            //First, try to load persitant cache store
+            PersistantCacheManager? pCManager = GetPersistantStore(plugin, config);
+
+            IBlobCacheTable table;
+
+            //See if the user defined a custom cache table implementation
+            if (config.TryGetValue(USER_CACHE_ASM_CONFIG_KEY, out JsonElement customEl))
+            {
+                string asmName = customEl.GetString() ?? throw new FileNotFoundException("User defined a custom blob cache assembly but the file name was null");
+
+                //Return the runtime loaded table
+                table = LoadCustomMemCacheTable(plugin, asmName, pCManager);
+            }
+            else
+            {
+                //Default type
+                table =  GetInternalBlobCache(heap, cacheConf, pCManager);
+            }
+
+            //Initialize the subsystem from the cache table
+            pCManager?.InitializeSubsystem(table);
+
+            return table;
+        }
+
+        private static IBlobCacheTable GetInternalBlobCache(IUnmangedHeap heap, CacheConfiguration config, IPersistantCacheStore? store)
+        {
+            return new BlobCacheTable(config.BucketCount, config.MaxCacheEntries, heap, store);
+        }
+
+        private static IBlobCacheTable LoadCustomMemCacheTable(PluginBase plugin, string asmName, IPersistantCacheStore? store)
+        {
+            //Load the custom assembly
+            AssemblyLoader<IBlobCacheTable> customTable = plugin.LoadAssembly<IBlobCacheTable>(asmName);
+
+            try
+            {
+                //Try get onload method and pass the persistant cache instance
+                Action<PluginBase, IPersistantCacheStore?>? onLoad = customTable.TryGetMethod<Action<PluginBase, IPersistantCacheStore?>>(LOAD_METHOD_NAME);
+                onLoad?.Invoke(plugin, store);
+            }
+            catch
+            {
+                customTable.Dispose();
+                throw;
+            }
+
+            return new RuntimeBlobCacheTable(customTable);
+        }
+
+        private static PersistantCacheManager? GetPersistantStore(PluginBase plugin, IConfigScope config)
+        {
+            //Get the persistant assembly 
+            if (!config.TryGetValue(PERSISTANT_ASM_CONFIF_KEY, out JsonElement asmEl))
+            {
+                return null;
+            }
+
+            string? asmName = asmEl.GetString();
+            if (asmName == null)
+            {
+                return null;
+            }
+
+            //Load the dynamic assembly into the alc
+            AssemblyLoader<IPersistantCacheStore> loader = plugin.LoadAssembly<IPersistantCacheStore>(asmName);
+            try
+            {
+                //Call the OnLoad method
+                Action<PluginBase, IConfigScope>? loadMethod = loader.TryGetMethod<Action<PluginBase, IConfigScope>>(LOAD_METHOD_NAME);
+
+                loadMethod?.Invoke(plugin, config);
+            }
+            catch
+            {
+                loader.Dispose();
+                throw;
+            }
+
+            //Return the 
+            return new(loader);
+        }
+      
+
+        private sealed class RuntimeBlobCacheTable : IBlobCacheTable 
+        {
+
+            private readonly IBlobCacheTable _table;
+            private readonly Action? OnDetatch;
+
+            public RuntimeBlobCacheTable(AssemblyLoader<IBlobCacheTable> loader)
+            {
+                OnDetatch = loader.TryGetMethod<Action>(TEARDOWN_METHOD_NAME);
+                _table = loader.Resource;
+            }
+
+            public void Dispose()
+            {
+                //We can let the loader dispose the cache table, but we can notify of detatch
+                OnDetatch?.Invoke();
+            }
+
+
+            ///<inheritdoc/>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            IBlobCacheBucket IBlobCacheTable.GetBucket(ReadOnlySpan<char> objectId) => _table.GetBucket(objectId);
+
+            ///<inheritdoc/>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public IEnumerator<IBlobCacheBucket> GetEnumerator() => _table.GetEnumerator();
+
+            ///<inheritdoc/>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            IEnumerator IEnumerable.GetEnumerator() => ((IEnumerable)_table).GetEnumerator();
+        }
+
+        internal sealed class PersistantCacheManager : IPersistantCacheStore
+        {
+            const string INITIALIZE_METHOD_NAME = "OnInitializeForBucket";
+           
+
+            /*
+             * Our referrence can be technically unloaded, but so will 
+             * this instance, since its loaded into the current ALC, so 
+             * this referrence may exist for the lifetime of this instance.
+             * 
+             * It also implements IDisposable, which the assembly loader class
+             * will call when this plugin is unloaded, we dont need to call
+             * it here, but we can signal a detach.
+             * 
+             * Since the store implements IDisposable, its likely going to 
+             * check for dispose on each call, so we don't need to add
+             * and additional disposed check since the method calls must be fast.
+             */
+
+            private readonly IPersistantCacheStore store;
+
+            private readonly Action<uint>? InitMethod;
+            private readonly Action? OnServiceDetatch;
+
+            public PersistantCacheManager(AssemblyLoader<IPersistantCacheStore> loader)
+            {
+                //Try to get the Initialize method
+                InitMethod = loader.TryGetMethod<Action<uint>>(INITIALIZE_METHOD_NAME);
+
+                //Get the optional detatch method
+                OnServiceDetatch = loader.TryGetMethod<Action>(TEARDOWN_METHOD_NAME);
+
+                store = loader.Resource;
+            }
+
+            /// <summary>
+            /// Optionally initializes the backing store by publishing the table's bucket 
+            /// id's so it's made aware of the memory cache bucket system.
+            /// </summary>
+            /// <param name="table">The table containing buckets to publish</param>
+            public void InitializeSubsystem(IBlobCacheTable table)
+            {
+                //Itterate all buckets
+                foreach (IBlobCacheBucket bucket in table)
+                {
+                    InitMethod?.Invoke(bucket.Id);
+                }
+            }
+
+            void IDisposable.Dispose()
+            {
+                //Assembly loader will dispose the type, we can just signal a detach
+
+                OnServiceDetatch?.Invoke();
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            bool IPersistantCacheStore.OnCacheMiss(uint bucketId, string key, IMemoryCacheEntryFactory factory, out CacheEntry entry)
+            {
+                return store.OnCacheMiss(bucketId, key, factory, out entry);
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            void IPersistantCacheStore.OnEntryDeleted(uint bucketId, string key) => store.OnEntryDeleted(bucketId, key);
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            void IPersistantCacheStore.OnEntryEvicted(uint bucketId, string key, in CacheEntry entry) => store.OnEntryEvicted(bucketId, key, in entry);
+        }
+    }
+}