Fix Azure ServiceBus persistent container support

src/Aspire.Hosting.Azure.ServiceBus/AzureServiceBusExtensions.cs

@@ -228,6 +228,11 @@ public static IResourceBuilder<AzureServiceBusResource> AddSubscription(this IRe
     /// </example>
     public static IResourceBuilder<AzureServiceBusResource> RunAsEmulator(this IResourceBuilder<AzureServiceBusResource> builder, Action<IResourceBuilder<AzureServiceBusEmulatorResource>>? configureContainer = null)
     {
+        if (builder.Resource.IsEmulator)
+        {
+            throw new InvalidOperationException("The Azure Service Bus resource is already configured to run as an emulator.");
+        }
+
         if (builder.ApplicationBuilder.ExecutionContext.IsPublishMode)
         {
             return builder;
@@ -275,9 +280,6 @@ public static IResourceBuilder<AzureServiceBusResource> RunAsEmulator(this IReso
 
         var aspireStore = AspireStore.Create(builder.ApplicationBuilder);
 
-        // Deterministic file path for the configuration file
-        var configHostFile = aspireStore.GetOrCreateFile($"{builder.Resource.Name}-Config.json");
-
         if (configureContainer != null)
         {
             var surrogate = new AzureServiceBusEmulatorResource(builder.Resource);
@@ -292,131 +294,35 @@ public static IResourceBuilder<AzureServiceBusResource> RunAsEmulator(this IReso
 
         sqlEdgeResource = sqlEdgeResource.WithLifetime(lifetime);
 
-        var defaultConfigFileMount = new ContainerMountAnnotation(
-                configHostFile,
-                AzureServiceBusEmulatorResource.EmulatorConfigJsonPath,
-                ContainerMountType.BindMount,
-                isReadOnly: true);
-
-        var hasCustomConfigJson = builder.Resource.Annotations.OfType<ContainerMountAnnotation>().Any(v => v.Target == AzureServiceBusEmulatorResource.EmulatorConfigJsonPath);
-
-        if (!hasCustomConfigJson)
-        {
-            builder.WithAnnotation(defaultConfigFileMount);
-        }
+        // RunAsEmulator() can be followed by custom model configuration so we need to delay the creation of the Config.json file
+        // until all resources are about to be prepared and annotations can't be updated anymore.
 
-        builder.ApplicationBuilder.Eventing.Subscribe<BeforeResourceStartedEvent>(builder.Resource, async (@event, ct) =>
+        builder.ApplicationBuilder.Eventing.Subscribe<BeforeResourcesPreparedEvent>((@event, ct) =>
         {
-            var serviceBusEmulatorResources = builder.ApplicationBuilder.Resources.OfType<AzureServiceBusResource>().Where(x => x is { } serviceBusResource && serviceBusResource.IsEmulator);
-
-            if (!serviceBusEmulatorResources.Any())
-            {
-                // No-op if there is no Azure Service Bus emulator resource.
-                return;
-            }
+            // Create JSON configuration file
 
-            var connectionString = await builder.Resource.ConnectionStringExpression.GetValueAsync(ct).ConfigureAwait(false);
+            var hasCustomConfigJson = builder.Resource.Annotations.OfType<ContainerMountAnnotation>().Any(v => v.Target == AzureServiceBusEmulatorResource.EmulatorConfigJsonPath);
 
-            if (connectionString == null)
+            if (hasCustomConfigJson)
             {
-                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{builder.Resource.Name}' resource but the connection string was null.");
+                return Task.CompletedTask;
             }
 
-            // Retrieve a queue/topic name to configure the health check
-
-            var noRetryOptions = new ServiceBusClientOptions { RetryOptions = new ServiceBusRetryOptions { MaxRetries = 0 } };
-            serviceBusClient = new ServiceBusClient(connectionString, noRetryOptions);
-
-            queueOrTopicName =
-                serviceBusEmulatorResources.SelectMany(x => x.Queues).Select(x => x.Name).FirstOrDefault()
-                ?? serviceBusEmulatorResources.SelectMany(x => x.Topics).Select(x => x.Name).FirstOrDefault();
-
-            // Create JSON configuration file
+            // Create Config.json file content and its alterations in a temporary file
+            var tempConfigFile = WriteEmulatorConfigJson(builder.Resource);
 
-            foreach (var emulatorResource in serviceBusEmulatorResources)
+            try
             {
-                var configFileMount = emulatorResource.Annotations.OfType<ContainerMountAnnotation>().Single(v => v.Target == AzureServiceBusEmulatorResource.EmulatorConfigJsonPath);
-
-                // If there is a custom mount for EmulatorConfigJsonPath we don't need to create the Config.json file.
-                if (configFileMount != defaultConfigFileMount)
-                {
-                    continue;
-                }
-
-                // Truncate the file since we are going to write to it.
-                var fileStreamOptions = new FileStreamOptions() { Mode = FileMode.Truncate, Access = FileAccess.Write };
-
-                using (var stream = new FileStream(configFileMount.Source!, fileStreamOptions))
-                {
-                    using var writer = new Utf8JsonWriter(stream, new JsonWriterOptions { Indented = true });
-
-                    writer.WriteStartObject();                      // {
-                    writer.WriteStartObject("UserConfig");          //   "UserConfig": {
-                    writer.WriteStartArray("Namespaces");           //     "Namespaces": [
-                    writer.WriteStartObject();                      //       {
-                    writer.WriteString("Name", emulatorResource.Name);
-                    writer.WriteStartArray("Queues");               //         "Queues": [
-
-                    foreach (var queue in emulatorResource.Queues)
-                    {
-                        writer.WriteStartObject();
-                        queue.WriteJsonObjectProperties(writer);
-                        writer.WriteEndObject();
-                    }
-
-                    writer.WriteEndArray();                         //         ] (/Queues)
-
-                    writer.WriteStartArray("Topics");               //         "Topics": [
-                    foreach (var topic in emulatorResource.Topics)
-                    {
-                        writer.WriteStartObject();                  //           "{ (Topic)"
-                        topic.WriteJsonObjectProperties(writer);
-
-                        writer.WriteStartArray("Subscriptions");    //             "Subscriptions": [
-                        foreach (var subscription in topic.Subscriptions)
-                        {
-                            writer.WriteStartObject();              //               "{ (Subscription)"
-                            subscription.WriteJsonObjectProperties(writer);
-
-                            writer.WriteStartArray("Rules");        //                 "Rules": [
-                            foreach (var rule in subscription.Rules)
-                            {
-                                writer.WriteStartObject();
-                                rule.WriteJsonObjectProperties(writer);
-                                writer.WriteEndObject();
-                            }
-
-                            writer.WriteEndArray();                 //                  ] (/Rules)
-
-                            writer.WriteEndObject();                //               } (/Subscription)
-                        }
-
-                        writer.WriteEndArray();                     //             ] (/Subscriptions)
-
-                        writer.WriteEndObject();                    //           } (/Topic)
-                    }
-                    writer.WriteEndArray();                         //         ] (/Topics)
-
-                    writer.WriteEndObject();                        //       } (/Namespace)
-                    writer.WriteEndArray();                         //     ], (/Namespaces)
-                    writer.WriteStartObject("Logging");             //     "Logging": {
-                    writer.WriteString("Type", "File");             //       "Type": "File"
-                    writer.WriteEndObject();                        //     } (/LoggingConfig)
-
-                    writer.WriteEndObject();                        //   } (/UserConfig)
-                    writer.WriteEndObject();                        // } (/Root)
-                }
-
                 // Apply ConfigJsonAnnotation modifications
-                var configJsonAnnotations = emulatorResource.Annotations.OfType<ConfigJsonAnnotation>();
+                var configJsonAnnotations = builder.Resource.Annotations.OfType<ConfigJsonAnnotation>();
 
                 foreach (var annotation in configJsonAnnotations)
                 {
-                    using var readStream = new FileStream(configFileMount.Source!, FileMode.Open, FileAccess.Read);
+                    using var readStream = new FileStream(tempConfigFile, FileMode.Open, FileAccess.Read);
                     var jsonObject = JsonNode.Parse(readStream);
                     readStream.Close();
 
-                    using var writeStream = new FileStream(configFileMount.Source!, FileMode.Open, FileAccess.Write);
+                    using var writeStream = new FileStream(tempConfigFile, FileMode.Open, FileAccess.Write);
                     using var writer = new Utf8JsonWriter(writeStream, new JsonWriterOptions { Indented = true });
 
                     if (jsonObject == null)
@@ -426,7 +332,41 @@ public static IResourceBuilder<AzureServiceBusResource> RunAsEmulator(this IReso
                     annotation.Configure(jsonObject);
                     jsonObject.WriteTo(writer);
                 }
+
+                // Deterministic file path for the configuration file based on its content
+                var configJsonPath = aspireStore.GetFileNameWithContent($"{builder.Resource.Name}-Config.json", tempConfigFile);
+
+                builder.WithAnnotation(new ContainerMountAnnotation(
+                    configJsonPath,
+                    AzureServiceBusEmulatorResource.EmulatorConfigJsonPath,
+                    ContainerMountType.BindMount,
+                    isReadOnly: true));
+            }
+            finally
+            {
+                File.Delete(tempConfigFile);
+            }
+
+            return Task.CompletedTask;
+        });
+
+        builder.ApplicationBuilder.Eventing.Subscribe<BeforeResourceStartedEvent>(builder.Resource, async (@event, ct) =>
+        {
+            var connectionString = await builder.Resource.ConnectionStringExpression.GetValueAsync(ct).ConfigureAwait(false);
+
+            if (connectionString == null)
+            {
+                throw new DistributedApplicationException($"ConnectionStringAvailableEvent was published for the '{builder.Resource.Name}' resource but the connection string was null.");
             }
+
+            // Retrieve a queue/topic name to configure the health check
+
+            var noRetryOptions = new ServiceBusClientOptions { RetryOptions = new ServiceBusRetryOptions { MaxRetries = 0 } };
+            serviceBusClient = new ServiceBusClient(connectionString, noRetryOptions);
+
+            queueOrTopicName =
+                builder.Resource.Queues.Select(x => x.Name).FirstOrDefault()
+                ?? builder.Resource.Topics.Select(x => x.Name).FirstOrDefault();
         });
 
         var healthCheckKey = $"{builder.Resource.Name}_check";
@@ -497,4 +437,70 @@ public static IResourceBuilder<AzureServiceBusEmulatorResource> WithHostPort(thi
             endpoint.Port = port;
         });
     }
+
+    private static string WriteEmulatorConfigJson(AzureServiceBusResource emulatorResource)
+    {
+        var filePath = Path.GetTempFileName();
+
+        using var stream = new FileStream(filePath, FileMode.Open, FileAccess.Write);
+        using var writer = new Utf8JsonWriter(stream, new JsonWriterOptions { Indented = true });
+
+        writer.WriteStartObject();                      // {
+        writer.WriteStartObject("UserConfig");          //   "UserConfig": {
+        writer.WriteStartArray("Namespaces");           //     "Namespaces": [
+        writer.WriteStartObject();                      //       {
+        writer.WriteString("Name", emulatorResource.Name);
+        writer.WriteStartArray("Queues");               //         "Queues": [
+
+        foreach (var queue in emulatorResource.Queues)
+        {
+            writer.WriteStartObject();
+            queue.WriteJsonObjectProperties(writer);
+            writer.WriteEndObject();
+        }
+
+        writer.WriteEndArray();                         //         ] (/Queues)
+
+        writer.WriteStartArray("Topics");               //         "Topics": [
+        foreach (var topic in emulatorResource.Topics)
+        {
+            writer.WriteStartObject();                  //           "{ (Topic)"
+            topic.WriteJsonObjectProperties(writer);
+
+            writer.WriteStartArray("Subscriptions");    //             "Subscriptions": [
+            foreach (var subscription in topic.Subscriptions)
+            {
+                writer.WriteStartObject();              //               "{ (Subscription)"
+                subscription.WriteJsonObjectProperties(writer);
+
+                writer.WriteStartArray("Rules");        //                 "Rules": [
+                foreach (var rule in subscription.Rules)
+                {
+                    writer.WriteStartObject();
+                    rule.WriteJsonObjectProperties(writer);
+                    writer.WriteEndObject();
+                }
+
+                writer.WriteEndArray();                 //                  ] (/Rules)
+
+                writer.WriteEndObject();                //               } (/Subscription)
+            }
+
+            writer.WriteEndArray();                     //             ] (/Subscriptions)
+
+            writer.WriteEndObject();                    //           } (/Topic)
+        }
+        writer.WriteEndArray();                         //         ] (/Topics)
+
+        writer.WriteEndObject();                        //       } (/Namespace)
+        writer.WriteEndArray();                         //     ], (/Namespaces)
+        writer.WriteStartObject("Logging");             //     "Logging": {
+        writer.WriteString("Type", "File");             //       "Type": "File"
+        writer.WriteEndObject();                        //     } (/LoggingConfig)
+
+        writer.WriteEndObject();                        //   } (/UserConfig)
+        writer.WriteEndObject();                        // } (/Root)
+
+        return filePath;
+    }
 }

src/Aspire.Hosting/ApplicationModel/BeforeResourcesPreparedEvent.cs

@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Aspire.Hosting.Eventing;
+
+namespace Aspire.Hosting.ApplicationModel;
+
+/// <summary>
+/// This event is raised by orchestrators before the resources are prepared.
+/// </summary>
+public class BeforeResourcesPreparedEvent() : IDistributedApplicationEvent
+{
+}

src/Aspire.Hosting/Dcp/DcpExecutor.cs

@@ -135,6 +135,8 @@ public async Task RunApplicationAsync(CancellationToken cancellationToken = defa
 
         try
         {
+            await _executorEvents.PublishAsync(new OnResourcesPreparingContext(cancellationToken)).ConfigureAwait(false);
+
             PrepareServices();
             PrepareContainers();
             PrepareExecutables();

src/Aspire.Hosting/Dcp/DcpExecutorEvents.cs

@@ -9,6 +9,7 @@ namespace Aspire.Hosting.Dcp;
 internal record ResourceStatus(string? State, DateTime? StartupTimestamp, DateTime? FinishedTimestamp);
 internal record OnEndpointsAllocatedContext(CancellationToken CancellationToken);
 internal record OnResourceStartingContext(CancellationToken CancellationToken, string ResourceType, IResource Resource, string? DcpResourceName);
+internal record OnResourcesPreparingContext(CancellationToken CancellationToken);
 internal record OnResourcesPreparedContext(CancellationToken CancellationToken);
 internal record OnResourceChangedContext(CancellationToken CancellationToken, string ResourceType, IResource Resource, string DcpResourceName, ResourceStatus Status, Func<CustomResourceSnapshot, CustomResourceSnapshot> UpdateSnapshot);
 internal record OnResourceFailedToStartContext(CancellationToken CancellationToken, string ResourceType, IResource Resource, string? DcpResourceName);

src/Aspire.Hosting/Orchestrator/ApplicationOrchestrator.cs

@@ -41,6 +41,7 @@ public ApplicationOrchestrator(DistributedApplicationModel model,
 
         dcpExecutorEvents.Subscribe<OnEndpointsAllocatedContext>(OnEndpointsAllocated);
         dcpExecutorEvents.Subscribe<OnResourceStartingContext>(OnResourceStarting);
+        dcpExecutorEvents.Subscribe<OnResourcesPreparingContext>(OnResourcesPreparing);
         dcpExecutorEvents.Subscribe<OnResourcesPreparedContext>(OnResourcesPrepared);
         dcpExecutorEvents.Subscribe<OnResourceChangedContext>(OnResourceChanged);
         dcpExecutorEvents.Subscribe<OnResourceFailedToStartContext>(OnResourceFailedToStart);
@@ -94,6 +95,12 @@ await _notificationService.PublishUpdateAsync(context.Resource, s => s with
         await _eventing.PublishAsync(beforeResourceStartedEvent, context.CancellationToken).ConfigureAwait(false);
     }
 
+    private async Task OnResourcesPreparing(OnResourcesPreparingContext context)
+    {
+        var beforeResourcePreparedEvent = new BeforeResourcesPreparedEvent();
+        await _eventing.PublishAsync(beforeResourcePreparedEvent, context.CancellationToken).ConfigureAwait(false);
+    }
+
     private async Task OnResourcesPrepared(OnResourcesPreparedContext _)
     {
         await PublishResourcesWithInitialStateAsync().ConfigureAwait(false);

src/Aspire.Hosting/PublicAPI.Unshipped.txt

@@ -1,4 +1,6 @@
 #nullable enable
+Aspire.Hosting.ApplicationModel.BeforeResourcesPreparedEvent
+Aspire.Hosting.ApplicationModel.BeforeResourcesPreparedEvent.BeforeResourcesPreparedEvent() -> void
 Aspire.Hosting.ApplicationModel.ContainerLifetime.Session = 0 -> Aspire.Hosting.ApplicationModel.ContainerLifetime
 Aspire.Hosting.ApplicationModel.CustomResourceSnapshot.HealthStatus.get -> Microsoft.Extensions.Diagnostics.HealthChecks.HealthStatus?
 Aspire.Hosting.ApplicationModel.CustomResourceSnapshot.Relationships.get -> System.Collections.Immutable.ImmutableArray<Aspire.Hosting.ApplicationModel.RelationshipSnapshot!>