Update discord example

examples/301-discord-test-application/301-discord-test-application.csproj

@@ -12,8 +12,8 @@
 
     <ItemGroup>
         <PackageReference Include="Aspire.Npgsql.EntityFrameworkCore.PostgreSQL" Version="9.0.0" />
-        <PackageReference Include="Discord.Net" Version="3.17.0" />
-        <PackageReference Include="Microsoft.KernelMemory.Service.AspNetCore" Version="0.96.250116.1" />
+        <PackageReference Include="Discord.Net" Version="3.17.1" />
+        <PackageReference Include="Microsoft.KernelMemory.Service.AspNetCore" Version="0.96.250120.1" />
     </ItemGroup>
 
 </Project>

examples/301-discord-test-application/DiscordDbContext.cs

@@ -8,6 +8,7 @@ public class DiscordDbContext : DbContext
 {
     public DbContextOptions<DiscordDbContext> Options { get; }
 
+    // Table to store Discord messages, table name is "Messages"
     public DbSet<DiscordDbMessage> Messages { get; set; }
 
     public DiscordDbContext(DbContextOptions<DiscordDbContext> options) : base(options)

examples/301-discord-test-application/DiscordMessageHandler.cs

@@ -12,7 +12,7 @@ namespace Microsoft.Discord.TestApplication;
 /// KM pipeline handler fetching discord data files from document storage
 /// and storing messages in Postgres.
 /// </summary>
-public sealed class DiscordMessageHandler : IPipelineStepHandler, IDisposable, IAsyncDisposable
+public sealed class DiscordMessageHandler : IPipelineStepHandler, IDisposable
 {
     // Name of the file where to store Discord data
     private readonly string _filename;
@@ -23,8 +23,11 @@ public sealed class DiscordMessageHandler : IPipelineStepHandler, IDisposable, I
     // .NET service provider, used to get thread safe instances of EF DbContext
     private readonly IServiceProvider _serviceProvider;
 
-    // EF DbContext used to create the database
-    private DiscordDbContext? _firstInvokeDb;
+    // DB creation
+    private readonly object _dbCreation = new();
+    private bool _dbCreated = false;
+    private bool _useScope = false;
+    private readonly IServiceScope _dbScope;
 
     // .NET logger
     private readonly ILogger<DiscordMessageHandler> _log;
@@ -44,9 +47,16 @@ public DiscordMessageHandler(
         this._orchestrator = orchestrator;
         this._serviceProvider = serviceProvider;
         this._filename = config.FileName;
+        this._dbScope = this._serviceProvider.CreateScope();
 
-        // This DbContext instance is used only to create the database
-        this._firstInvokeDb = serviceProvider.GetService<DiscordDbContext>() ?? throw new ConfigurationException("Discord DB Content is not defined");
+        try
+        {
+            this.OnFirstInvoke();
+        }
+        catch (Exception)
+        {
+            // ignore, will retry later
+        }
     }
 
     public async Task<(ReturnType returnType, DataPipeline updatedPipeline)> InvokeAsync(DataPipeline pipeline, CancellationToken cancellationToken = default)
@@ -57,8 +67,7 @@ public DiscordMessageHandler(
         // exception: System.InvalidOperationException: a second operation was started on this context instance before a previous
         // operation completed. This is usually caused by different threads concurrently using the same instance of DbContext.
         // For more information on how to avoid threading issues with DbContext, see https://go.microsoft.com/fwlink/?linkid=2097913.
-        DiscordDbContext? db = this._serviceProvider.GetService<DiscordDbContext>();
-        ArgumentNullExceptionEx.ThrowIfNull(db, nameof(db), "Discord DB context is NULL");
+        var db = this.GetDb();
         await using (db.ConfigureAwait(false))
         {
             foreach (DataPipeline.FileDetails uploadedFile in pipeline.Files)
@@ -95,27 +104,67 @@ public DiscordMessageHandler(
 
     public void Dispose()
     {
-        this._firstInvokeDb?.Dispose();
-        this._firstInvokeDb = null;
+        this._dbScope.Dispose();
     }
 
-    public async ValueTask DisposeAsync()
+    private void OnFirstInvoke()
     {
-        if (this._firstInvokeDb != null) { await this._firstInvokeDb.DisposeAsync(); }
+        if (this._dbCreated) { return; }
 
-        this._firstInvokeDb = null;
+        lock (this._dbCreation)
+        {
+            if (this._dbCreated) { return; }
+
+            var db = this.GetDb();
+            db.Database.EnsureCreated();
+            db.Dispose();
+            db = null;
+
+            this._dbCreated = true;
+
+            this._log.LogInformation("DB created");
+        }
     }
 
-    private void OnFirstInvoke()
+    /// <summary>
+    /// Depending on the hosting type, the DB Context is retrieved in different ways.
+    /// Single host app:
+    ///     db = _serviceProvider.GetService[DiscordDbContext](); // this throws an exception in multi-host mode
+    /// Multi host app:
+    ///     db = serviceProvider.CreateScope().ServiceProvider.GetRequiredService[DiscordDbContext]();
+    /// </summary>
+    private DiscordDbContext GetDb()
     {
-        if (this._firstInvokeDb == null) { return; }
+        DiscordDbContext? db;
 
-        lock (this._firstInvokeDb)
+        if (this._useScope)
         {
-            // Create DB / Tables if needed
-            this._firstInvokeDb.Database.EnsureCreated();
-            this._firstInvokeDb.Dispose();
-            this._firstInvokeDb = null;
+            db = this._dbScope.ServiceProvider.GetRequiredService<DiscordDbContext>();
         }
+        else
+        {
+            try
+            {
+                // Try the single app host first
+                this._log.LogTrace("Retrieving Discord DB context using service provider");
+                db = this._serviceProvider.GetService<DiscordDbContext>();
+            }
+            catch (InvalidOperationException)
+            {
+                // If the single app host fails, try the multi app host
+                this._log.LogInformation("Retrieving Discord DB context using scope");
+                db = this._dbScope.ServiceProvider.GetRequiredService<DiscordDbContext>();
+
+                // If the multi app host succeeds, set a flag to remember to use the scope
+                if (db != null)
+                {
+                    this._useScope = true;
+                }
+            }
+        }
+
+        ArgumentNullExceptionEx.ThrowIfNull(db, nameof(db), "Discord DB context is NULL");
+
+        return db;
     }
 }

examples/301-discord-test-application/Program.cs

@@ -2,11 +2,15 @@
 
 using Microsoft.KernelMemory;
 using Microsoft.KernelMemory.DocumentStorage.DevTools;
+using Microsoft.KernelMemory.MemoryStorage.DevTools;
 using Microsoft.KernelMemory.Sources.DiscordBot;
 
 namespace Microsoft.Discord.TestApplication;
 
 /* Example: Listen for new messages in Discord, and save them in a table in Postgres.
+ *
+ * Why this example: You can build on this example to populate a memory database with
+ *                   user messages, and then use the memory database to autogenerate answers.
  *
  * Use ASP.NET hosted services to host a Discord Bot. The discord bot logic is based
  * on DiscordConnector class.
@@ -18,8 +22,15 @@ namespace Microsoft.Discord.TestApplication;
  * The call to KM.ImportDocument API asks to process the JSON file uploaded using
  * DiscordMessageHandler, included in this project. No other handlers are used.
  *
- * DiscordMessageHandler, loads the uploaded file, deserializes its content, and
- * save each Discord message into a table in Postgres, using Entity Framework.
+ * DiscordMessageHandler, loads the JSON file uploaded, deserializes its content, and
+ * saves each Discord message into a table in Postgres, using Entity Framework.
+ *
+ * Discord Server
+ *   => Discord Bot
+ *      => OnMessage Event
+ *         => KM.ImportDocumentAsync(data, steps: ["store_discord_message"])
+ *            => DiscordMessageHandler
+ *               => Postgres table
  */
 
 internal static class Program
@@ -51,8 +62,8 @@ public static void Main(string[] args)
         appBuilder.AddNpgsqlDbContext<DiscordDbContext>("postgresDb");
 
         // Run Kernel Memory and DiscordMessageHandler
-        // var kmApp = BuildAsynchronousKernelMemoryApp(appBuilder, discordConfig);
-        var kmApp = BuildSynchronousKernelMemoryApp(appBuilder, discordCfg);
+        // var kmApp = BuildAsynchronousKernelMemoryApp(appBuilder, discordCfg); // run using queues and threads
+        var kmApp = BuildSynchronousKernelMemoryApp(appBuilder, discordCfg); // run everything in one thread
 
         Console.WriteLine("Starting KM application...\n");
         kmApp.Run();
@@ -65,8 +76,9 @@ private static WebApplication BuildSynchronousKernelMemoryApp(WebApplicationBuil
         {
             // Note: there's no queue system, so the memory instance will be synchronous (ie MemoryServerless)
 
-            // Store files on disk
+            // Store files and vectors on disk
             kmb.WithSimpleFileStorage(SimpleFileStorageConfig.Persistent);
+            kmb.WithSimpleVectorDb(SimpleVectorDbConfig.Persistent);
 
             // Disable AI, not needed for this example
             kmb.WithoutEmbeddingGenerator();
@@ -76,29 +88,33 @@ private static WebApplication BuildSynchronousKernelMemoryApp(WebApplicationBuil
         WebApplication app = appBuilder.Build();
 
         // In synchronous apps, handlers are added to the serverless memory orchestrator
-        (app.Services.GetService<IKernelMemory>() as MemoryServerless)!
-            .Orchestrator
-            .AddHandler<DiscordMessageHandler>(discordConfig.Steps[0]);
+        var orchestrator = (app.Services.GetService<IKernelMemory>() as MemoryServerless)!.Orchestrator;
+        orchestrator.AddHandler<DiscordMessageHandler>(discordConfig.Steps[0]);
 
         return app;
     }
 
     private static WebApplication BuildAsynchronousKernelMemoryApp(WebApplicationBuilder appBuilder, DiscordConnectorConfig discordConfig)
     {
-        appBuilder.Services.AddHandlerAsHostedService<DiscordMessageHandler>(discordConfig.Steps[0]);
         appBuilder.AddKernelMemory(kmb =>
         {
             // Note: because of this the memory instance will be asynchronous (ie MemoryService)
             kmb.WithSimpleQueuesPipeline();
 
-            // Store files on disk
+            // Store files and vectors on disk
             kmb.WithSimpleFileStorage(SimpleFileStorageConfig.Persistent);
+            kmb.WithSimpleVectorDb(SimpleVectorDbConfig.Persistent);
 
             // Disable AI, not needed for this example
             kmb.WithoutEmbeddingGenerator();
             kmb.WithoutTextGenerator();
         });
 
-        return appBuilder.Build();
+        // In asynchronous apps, handlers are added as hosted services to run on dedicated threads
+        appBuilder.Services.AddHandlerAsHostedService<DiscordMessageHandler>(discordConfig.Steps[0]);
+
+        WebApplication app = appBuilder.Build();
+
+        return app;
     }
 }

service/Abstractions/KernelMemoryBuilderBuildOptions.cs

@@ -4,5 +4,12 @@ namespace Microsoft.KernelMemory;
 
 public sealed class KernelMemoryBuilderBuildOptions
 {
+    public readonly static KernelMemoryBuilderBuildOptions Default = new();
+
+    public readonly static KernelMemoryBuilderBuildOptions WithVolatileAndPersistentData = new()
+    {
+        AllowMixingVolatileAndPersistentData = true
+    };
+
     public bool AllowMixingVolatileAndPersistentData { get; set; } = false;
 }

service/Service.AspNetCore/WebApplicationBuilderExtensions.cs

@@ -20,11 +20,13 @@ public static partial class WebApplicationBuilderExtensions
     /// <param name="configureMemoryBuilder">Optional configuration steps for the memory builder</param>
     /// <param name="configureMemory">Optional configuration steps for the memory instance</param>
     /// <param name="configureServices">Optional configuration for the internal dependencies</param>
+    /// <param name="buildOptions">Optional options passed to Build() call</param>
     public static WebApplicationBuilder AddKernelMemory(
         this WebApplicationBuilder appBuilder,
         Action<IKernelMemoryBuilder>? configureMemoryBuilder = null,
         Action<IKernelMemory>? configureMemory = null,
-        Action<IServiceCollection>? configureServices = null)
+        Action<IServiceCollection>? configureServices = null,
+        KernelMemoryBuilderBuildOptions? buildOptions = null)
     {
         // Prepare memory builder, sharing the service collection used by the hosting service
         var memoryBuilder = new KernelMemoryBuilder(appBuilder.Services);
@@ -35,7 +37,7 @@ public static WebApplicationBuilder AddKernelMemory(
         // Optional configuration provided by the user
         configureMemoryBuilder?.Invoke(memoryBuilder);
 
-        var memory = memoryBuilder.Build();
+        var memory = memoryBuilder.Build(buildOptions);
 
         // Optional memory configuration provided by the user
         configureMemory?.Invoke(memory);

service/tests/Core.UnitTests/KernelMemoryBuilderTest.cs

@@ -118,10 +118,7 @@ public void ItDetectsMissingEmbeddingGenerator()
     public void ItCanMixPersistentAndVolatileStorageIfNeeded()
     {
         // Arrange
-        KernelMemoryBuilderBuildOptions kmbOptions = new()
-        {
-            AllowMixingVolatileAndPersistentData = true
-        };
+        var kmbOptions = KernelMemoryBuilderBuildOptions.WithVolatileAndPersistentData;
 
         // Act - Assert no exception occurs
         new KernelMemoryBuilder()
@@ -136,11 +133,7 @@ public void ItCanMixPersistentAndVolatileStorageIfNeeded()
     public void ItCanMixPersistentAndVolatileStorageIfNeeded2()
     {
         // Arrange
-        KernelMemoryBuilderBuildOptions kmbOptions = new()
-        {
-            AllowMixingVolatileAndPersistentData = true
-        };
-
+        var kmbOptions = KernelMemoryBuilderBuildOptions.WithVolatileAndPersistentData;
         var serviceCollection1 = new ServiceCollection();
         var serviceCollection2 = new ServiceCollection();