Run Events handlers in the background

Author: SitholeWB

FilesAPI/Controllers/StorageController.cs

@@ -2,8 +2,8 @@
 using FilesAPI.ViewModels;
 using FilesAPI.ViewModels.Mapper;
 using Microsoft.AspNetCore.Mvc;
-using Microsoft.Extensions.DependencyInjection;
 using Models;
+using Services;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -17,10 +17,12 @@ namespace FilesAPI.Controllers;
 public class StorageController : ControllerBase
 {
     private readonly IStorageService _storageService;
+    private readonly EventHandlerContainer _eventContainer;
 
-    public StorageController(IStorageService storageService)
+    public StorageController(IStorageService storageService, EventHandlerContainer eventContainer)
     {
         _storageService = storageService;
+        _eventContainer = eventContainer;
     }
 
     //Example from https://dottutorials.net/dotnet-core-web-api-multipart-form-data-upload-file/
@@ -56,27 +58,8 @@ public async Task<IActionResult> DownLoadFile(string id, CancellationToken token
     {
         var (content, details) = await _storageService.DownloadFileAsync(id, token);
 
-        // Record analytics
-        var userAgent = Request.Headers["User-Agent"].ToString();
-        var ipAddress = HttpContext.Connection.RemoteIpAddress?.ToString();
-        var referrer = Request.Headers["Referer"].ToString();
-
-        // Fire and forget analytics recording
-        _ = Task.Run(async () =>
-        {
-            try
-            {
-                var analyticsService = HttpContext.RequestServices.GetService<IAnalyticsService>();
-                if (analyticsService != null)
-                {
-                    await analyticsService.RecordDownloadAsync(id, userAgent, ipAddress, referrer, "download", token);
-                }
-            }
-            catch
-            {
-                // Ignore analytics errors to not affect file download
-            }
-        }, token);
+        // Record analytics for view
+        await RecordAnalyticsAsync(details, token);
 
         this.Response.ContentLength = details.Size;
         this.Response.Headers["Accept-Ranges"] = "bytes";
@@ -90,26 +73,7 @@ public async Task<FileStreamResult> DownloadView(string id, CancellationToken to
         var (stream, details) = await _storageService.DownloadFileAsync(id, token);
 
         // Record analytics for view
-        var userAgent = Request.Headers["User-Agent"].ToString();
-        var ipAddress = HttpContext.Connection.RemoteIpAddress?.ToString();
-        var referrer = Request.Headers["Referer"].ToString();
-
-        // Fire and forget analytics recording
-        _ = Task.Run(async () =>
-        {
-            try
-            {
-                var analyticsService = HttpContext.RequestServices.GetService<IAnalyticsService>();
-                if (analyticsService != null)
-                {
-                    await analyticsService.RecordDownloadAsync(id, userAgent, ipAddress, referrer, "view", token);
-                }
-            }
-            catch
-            {
-                // Ignore analytics errors to not affect file download
-            }
-        }, token);
+        await RecordAnalyticsAsync(details, token);
 
         this.Response.ContentLength = details.Size;
         this.Response.Headers["Accept-Ranges"] = "bytes";
@@ -152,4 +116,22 @@ public async Task<ActionResult<string>> DeleteFileAsync(string id, CancellationT
         string deletedId = await _storageService.DeleteFileAsync(id, token);
         return Ok($"Deleted '{deletedId}' successfully.");
     }
+
+    private async Task RecordAnalyticsAsync(FileDetails details, CancellationToken token)
+    {
+        var userAgent = Request.Headers["User-Agent"].ToString();
+        var ipAddress = HttpContext.Connection.RemoteIpAddress?.ToString();
+        var referrer = Request.Headers["Referer"].ToString();
+        var enhancedFileDownloadedEvent = new EnhancedFileDownloadedEvent
+        {
+            DownloadMethod = "view",
+            DownloadStartTime = DateTime.UtcNow,
+            FileDetails = details,
+            UserAgent = userAgent,
+            IpAddress = ipAddress,
+            Referrer = referrer,
+            RequestId = HttpContext.TraceIdentifier
+        };
+        await _eventContainer.PublishAsync(enhancedFileDownloadedEvent, token);
+    }
 }

FilesAPI/Startup.cs

@@ -119,8 +119,10 @@ public void ConfigureServices(IServiceCollection services)
             services.AddSingleton<ISettingsService, SettingsService>();
 
             services.AddScoped<RecordDownloadHandler>();
+            services.AddScoped<RecordDownloadAnalyticsHandler>();
             services.AddScoped<EventHandlerContainer>();
             EventHandlerContainer.Subscribe<FileDownloadedEvent, RecordDownloadHandler>();
+            EventHandlerContainer.Subscribe<EnhancedFileDownloadedEvent, RecordDownloadAnalyticsHandler>();
 
             services.AddControllers();
         }

FilesAPI/database.db

@@ -3,7 +3,7 @@ namespace Models;
 /// <summary>
 /// Enhanced file download event with additional analytics data
 /// </summary>
-public class EnhancedFileDownloadedEvent
+public class EnhancedFileDownloadedEvent : EventBase
 {
     public FileDetails FileDetails { get; set; }
     public DateTime DownloadStartTime { get; set; }

Models/Events/EnhancedFileDownloadedEvent.cs

@@ -0,0 +1,32 @@
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Services;
+
+public class RecordDownloadAnalyticsHandler : IEventHandler<EnhancedFileDownloadedEvent>
+{
+    private readonly IServiceScopeFactory _scopeFactory;
+
+    public RecordDownloadAnalyticsHandler(IServiceScopeFactory scopeFactory)
+    {
+        _scopeFactory = scopeFactory;
+    }
+
+    public Task RunAsync(EnhancedFileDownloadedEvent obj, CancellationToken token)
+    {
+        _ = Task.Run(async () =>
+        {
+            //fire‑and‑forget
+            using var scope = _scopeFactory.CreateScope();
+            var analyticsService = scope.ServiceProvider.GetRequiredService<IAnalyticsService>();
+            await analyticsService.RecordDownloadAsync(
+                obj.FileDetails.Id,
+                obj.UserAgent,
+                obj.IpAddress,
+                obj.Referrer,
+                obj.DownloadMethod,
+                CancellationToken.None);
+        }, CancellationToken.None);
+
+        return Task.CompletedTask;
+    }
+}

Services/Events/Handlers/RecordDownloadAnalyticsHandler.cs

@@ -1,16 +1,26 @@
-namespace Services;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Services;
 
 public class RecordDownloadHandler : IEventHandler<FileDownloadedEvent>
 {
-    private readonly IStorageService _storageService;
+    private readonly IServiceScopeFactory _scopeFactory;
 
-    public RecordDownloadHandler(IStorageService storageService)
+    public RecordDownloadHandler(IServiceScopeFactory scopeFactory)
     {
-        _storageService = storageService;
+        _scopeFactory = scopeFactory;
     }
 
-    public async Task RunAsync(FileDownloadedEvent obj, CancellationToken token)
+    public Task RunAsync(FileDownloadedEvent obj, CancellationToken token)
     {
-        await _storageService.IncrementDownloadCountAsync(obj.FileDetails, token);
+        //fire‑and‑forget
+        _ = Task.Run(async () =>
+        {
+            using var scope = _scopeFactory.CreateScope();
+            var storageService = scope.ServiceProvider.GetRequiredService<IStorageService>();
+            await storageService.IncrementDownloadCountAsync(obj.FileDetails, CancellationToken.None);
+        }, CancellationToken.None);
+
+        return Task.CompletedTask;
     }
 }

Services/Events/Handlers/RecordDownloadHandler.cs

@@ -33,6 +33,10 @@ private void CreateIndexes(CancellationToken token = default)
 
     public async Task<DownloadAnalytics> AddDownloadRecordAsync(DownloadAnalytics analytics, CancellationToken token)
     {
+        if (string.IsNullOrEmpty(analytics.Id))
+        {
+            analytics.Id = ObjectId.NewObjectId().ToString();
+        }
         await _collection.InsertOneAsync(analytics, options: default, token);
         return analytics;
     }

Services/Repositories/MongoDbDownloadAnalyticsRepository.cs

@@ -14,8 +14,13 @@ public SqlDbDownloadAnalyticsRepository(FilesDbContext filesDbContext)
 
     public async Task<DownloadAnalytics> AddDownloadRecordAsync(DownloadAnalytics analytics, CancellationToken token)
     {
+        if (string.IsNullOrEmpty(analytics.Id))
+        {
+            analytics.Id = ObjectId.NewObjectId().ToString();
+        }
         await _filesDbContext.AddAsync(analytics, token);
         await _filesDbContext.SaveChangesAsync(token);
+
         return analytics;
     }