[WebPubSub] Make hub methods virtual. (Azure#25161)

# All SDK Contribution checklist:

This checklist is used to make sure that common guidelines for a pull request are followed.
- [ ] **Please open PR in `Draft` mode if it is:**
	- Work in progress or not intended to be merged.
	- Encountering multiple pipeline failures and working on fixes.
- [ ] If an SDK is being regenerated based on a new swagger spec, a link to the pull request containing these swagger spec changes has been included above.
- [ ] **I have read the [contribution guidelines](https://github.com/Azure/azure-sdk-for-net/blob/main/CONTRIBUTING.md).**
- [ ] **The pull request does not introduce [breaking changes](https://github.com/dotnet/corefx/blob/master/Documentation/coding-guidelines/breaking-change-rules.md).**

### [General Guidelines and Best Practices](https://github.com/Azure/azure-sdk-for-net/blob/main/CONTRIBUTING.md#general-guidelines)
- [ ] Title of the pull request is clear and informative.
- [ ] There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, [see this page](https://github.com/Azure/azure-powershell/blob/master/documentation/development-docs/cleaning-up-commits.md).

### [Testing Guidelines](https://github.com/Azure/azure-sdk-for-net/blob/main/CONTRIBUTING.md#testing-guidelines)
- [ ] Pull request includes test coverage for the included changes.

### [SDK Generation Guidelines](https://github.com/Azure/azure-sdk-for-net/blob/main/CONTRIBUTING.md#sdk-generation-guidelines)
- [ ] The generate.cmd file for the SDK has been updated with the version of AutoRest, as well as the commitid of your swagger spec or link to the swagger spec, used to generate the code. (Track 2 only)
- [ ] The `*.csproj` and `AssemblyInfo.cs` files have been updated with the new version of the SDK. Please double check nuget.org current release version.

## Additional management plane SDK specific contribution checklist: 
Note: Only applies to `Microsoft.Azure.Management.[RP]` or `Azure.ResourceManager.[RP]`
 
- [ ] Include updated [management metadata](https://github.com/Azure/azure-sdk-for-net/tree/main/eng/mgmt/mgmtmetadata).
- [ ] Update AzureRP.props to add/remove version info to maintain up to date API versions.

### Management plane SDK Troubleshooting
- If this is very first SDK for a services and you are adding new service folders directly under /SDK, please add `new service` label and/or contact assigned reviewer.
- If the check fails at the `Verify Code Generation` step, please ensure:
	- Do not modify any code in generated folders.
	- Do not selectively include/remove generated files in the PR.
	- Do use `generate.ps1/cmd` to generate this PR instead of calling `autorest` directly.
	Please pay attention to the @microsoft.csharp version output after running `generate.ps1`. If it is lower than current released version (2.3.82), please run it again as it should pull down the latest version.
	
	**Note: We have recently updated the PSH module called by `generate.ps1` to emit additional data. This would help reduce/eliminate the Code Verification check error. Please run following command**:

	    `dotnet msbuild eng/mgmt.proj /t:Util /p:UtilityName=InstallPsModules`

### Old outstanding PR cleanup
 Please note:
	If PRs (including draft) has been out for more than 60 days and there are no responses from our query or followups, they will be closed to maintain a concise list for our reviewers.

Author: JialinXin

sdk/webpubsub/Microsoft.Azure.WebPubSub.AspNetCore/README.md

@@ -45,6 +45,14 @@ var serviceClient = new WebPubSubServiceClient(new Uri(endpoint), "some_hub", ne
 
 For information about general Web PubSub concepts [Concepts in Azure Web PubSub](https://docs.microsoft.com/azure/azure-web-pubsub/key-concepts)
 
+### `WebPubSubHub`
+
+`WebPubSubHub` is an abstract class to let users implement the subscribed Web PubSub service events. After user register the [event handler](https://docs.microsoft.com/azure/azure-web-pubsub/howto-develop-eventhandler) in service side, these events will be forwarded from service to server. And `WebPubSubHub` provides 4 methods mapping to the service events to enable users deal with these events, for example, client management, validations or working with `Azure.Messaging.WebPubSub` to broadcast the messages. See samples below for details.
+
+> NOTE
+> 
+> Among the 4 methods, `OnConnectAsync()` and `OnMessageReceivedAsync()` are blocking events that service will respect server returns. Besides the mapped correct response, server can throw exceptions whenever the request is against the server side logic. And `UnauthorizedAccessException` will be converted to `401Unauthorized` and rest will be converted to `500InternalServerError` along with exception message to return service. Then service will drop current client connection.
+
 ## Examples
 
 ### Add Web PubSub service with options
@@ -76,13 +84,13 @@ public void Configure(IApplicationBuilder app)
 ### Handle Upstream event
 
 ```C#
-public override ValueTask<WebPubSubEventResponse> OnConnectAsync(ConnectEventRequest request, CancellationToken cancellationToken)
+public override ValueTask<ConnectEventResponse> OnConnectAsync(ConnectEventRequest request, CancellationToken cancellationToken)
 {
     var response = new ConnectEventResponse
     {
         UserId = request.ConnectionContext.UserId
     };
-    return new ValueTask<WebPubSubEventResponse>(response);
+    return new ValueTask<ConnectEventResponse>(response);
 }
 ```
 

sdk/webpubsub/Microsoft.Azure.WebPubSub.AspNetCore/api/Microsoft.Azure.WebPubSub.AspNetCore.netcoreapp3.1.cs

@@ -10,20 +10,16 @@ namespace Microsoft.Azure.WebPubSub.AspNetCore
     public abstract partial class WebPubSubHub
     {
         protected WebPubSubHub() { }
-        public abstract System.Threading.Tasks.ValueTask<Microsoft.Azure.WebPubSub.Common.WebPubSubEventResponse> OnConnectAsync(Microsoft.Azure.WebPubSub.Common.ConnectEventRequest request, System.Threading.CancellationToken cancellationToken);
+        public virtual System.Threading.Tasks.ValueTask<Microsoft.Azure.WebPubSub.Common.ConnectEventResponse> OnConnectAsync(Microsoft.Azure.WebPubSub.Common.ConnectEventRequest request, System.Threading.CancellationToken cancellationToken) { throw null; }
         public virtual System.Threading.Tasks.Task OnConnectedAsync(Microsoft.Azure.WebPubSub.Common.ConnectedEventRequest request) { throw null; }
         public virtual System.Threading.Tasks.Task OnDisconnectedAsync(Microsoft.Azure.WebPubSub.Common.DisconnectedEventRequest request) { throw null; }
-        public abstract System.Threading.Tasks.ValueTask<Microsoft.Azure.WebPubSub.Common.WebPubSubEventResponse> OnMessageReceivedAsync(Microsoft.Azure.WebPubSub.Common.UserEventRequest request, System.Threading.CancellationToken cancellationToken);
+        public virtual System.Threading.Tasks.ValueTask<Microsoft.Azure.WebPubSub.Common.UserEventResponse> OnMessageReceivedAsync(Microsoft.Azure.WebPubSub.Common.UserEventRequest request, System.Threading.CancellationToken cancellationToken) { throw null; }
     }
     public partial class WebPubSubOptions
     {
         public WebPubSubOptions() { }
         public Microsoft.Azure.WebPubSub.AspNetCore.WebPubSubValidationOptions ValidationOptions { get { throw null; } set { } }
     }
-    public static partial class WebPubSubRequestExtensions
-    {
-        public static System.Threading.Tasks.Task<Microsoft.Azure.WebPubSub.Common.WebPubSubEventRequest> ReadWebPubSubEventAsync(this Microsoft.AspNetCore.Http.HttpRequest request, Microsoft.Azure.WebPubSub.AspNetCore.WebPubSubValidationOptions options = null, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
-    }
     public partial class WebPubSubValidationOptions
     {
         public WebPubSubValidationOptions(System.Collections.Generic.IEnumerable<string> connectionStrings) { }

sdk/webpubsub/Microsoft.Azure.WebPubSub.AspNetCore/api/Microsoft.Azure.WebPubSub.AspNetCore.netstandard2.0.cs

@@ -1,9 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT License.
-#if NETCOREAPP3_0_OR_GREATER
 using System;
 using Microsoft.Azure.WebPubSub.AspNetCore;
-using Microsoft.Extensions.DependencyInjection.Extensions;
 
 namespace Microsoft.Extensions.DependencyInjection
 {
@@ -54,4 +52,3 @@ public static IServiceCollection AddWebPubSub(this IServiceCollection services)
         }
     }
 }
-#endif

sdk/webpubsub/Microsoft.Azure.WebPubSub.AspNetCore/src/Extensions/WebPubSubDependencyInjectionExtensions.cs

@@ -1,5 +1,4 @@
-#if NETCOREAPP3_0_OR_GREATER
-using System;
+using System;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.Azure.WebPubSub.AspNetCore;
 using Microsoft.Extensions.DependencyInjection;
@@ -45,5 +44,4 @@ public static IEndpointConventionBuilder MapWebPubSubHub<THub>(
             return endpoints.Map(path, app.Build());
         }
     }
-}
-#endif
+}

sdk/webpubsub/Microsoft.Azure.WebPubSub.AspNetCore/src/Extensions/WebPubSubEndpointRouteBuilderExtensions.cs

@@ -21,7 +21,7 @@ namespace Microsoft.Azure.WebPubSub.AspNetCore
     /// <summary>
     /// Helper methods to parse upstream requests.
     /// </summary>
-    public static class WebPubSubRequestExtensions
+    internal static class WebPubSubRequestExtensions
     {
         /// <summary>
         /// Parse request to system/user type ServiceRequest.
@@ -30,7 +30,7 @@ public static class WebPubSubRequestExtensions
         /// <param name="options"></param>
         /// <param name="cancellationToken"></param>
         /// <returns>Deserialize <see cref="WebPubSubEventRequest"/></returns>
-        public static async Task<WebPubSubEventRequest> ReadWebPubSubEventAsync(this HttpRequest request, WebPubSubValidationOptions options = null, CancellationToken cancellationToken = default)
+        internal static async Task<WebPubSubEventRequest> ReadWebPubSubEventAsync(this HttpRequest request, WebPubSubValidationOptions options = null, CancellationToken cancellationToken = default)
         {
             if (request == null)
             {

sdk/webpubsub/Microsoft.Azure.WebPubSub.AspNetCore/src/Extensions/WebPubSubRequestExtensions.cs

@@ -9,6 +9,7 @@
 using Microsoft.AspNetCore.Http;
 using Microsoft.Azure.WebPubSub.Common;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 
 namespace Microsoft.Azure.WebPubSub.AspNetCore
@@ -17,21 +18,16 @@ internal class ServiceRequestHandlerAdapter
     {
         private readonly WebPubSubOptions _options;
         private readonly IServiceProvider _provider;
+        private readonly ILogger _logger;
 
         // <hubName, HubImpl>
         private readonly Dictionary<string, WebPubSubHub> _hubRegistry = new(StringComparer.OrdinalIgnoreCase);
 
-        public ServiceRequestHandlerAdapter(IServiceProvider provider, IOptions<WebPubSubOptions> options)
+        public ServiceRequestHandlerAdapter(IServiceProvider provider, IOptions<WebPubSubOptions> options, ILogger<ServiceRequestHandlerAdapter> logger)
         {
-            _provider = provider;
+            _provider = provider ?? throw new ArgumentNullException(nameof(provider));
             _options = options.Value;
-        }
-
-        // for tests.
-        internal ServiceRequestHandlerAdapter(WebPubSubOptions options, WebPubSubHub hub)
-        {
-            _options = options;
-            _hubRegistry.Add(hub.GetType().Name, hub);
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
         }
 
         public void RegisterHub<THub>() where THub : WebPubSubHub
@@ -81,6 +77,7 @@ public async Task HandleRequest(HttpContext context)
             try
             {
                 var serviceRequest = await request.ReadWebPubSubEventAsync(_options.ValidationOptions, context.RequestAborted);
+                Log.StartToHandleRequest(_logger, serviceRequest.ConnectionContext);
 
                 switch (serviceRequest)
                 {
@@ -90,71 +87,66 @@ public async Task HandleRequest(HttpContext context)
                             if (preflightRequest.IsValid)
                             {
                                 context.Response.Headers.Add(Constants.Headers.WebHookAllowedOrigin, Constants.AllowedAllOrigins);
-                                return;
+                                break;
                             }
                             context.Response.StatusCode = StatusCodes.Status400BadRequest;
                             await context.Response.WriteAsync("Abuse Protection validation failed.").ConfigureAwait(false);
-                            return;
+                            break;
                         }
                     case ConnectEventRequest connectEventRequest:
                         {
                             var response = await hub.OnConnectAsync(connectEventRequest, context.RequestAborted).ConfigureAwait(false);
-                            if (response is EventErrorResponse error)
+                            // default as null is allowed.
+                            if (response != null)
                             {
-                                context.Response.StatusCode = ConvertToStatusCode(error.Code);
-                                context.Response.ContentType = Constants.ContentTypes.PlainTextContentType;
-                                await context.Response.WriteAsync(error.ErrorMessage).ConfigureAwait(false);
-                                return;
+                                SetConnectionState(ref context, connectEventRequest.ConnectionContext, response.States);
+                                await context.Response.WriteAsync(JsonSerializer.Serialize(response)).ConfigureAwait(false);
                             }
-                            else if (response is ConnectEventResponse connectResponse)
-                            {
-                                SetConnectionState(ref context, connectEventRequest.ConnectionContext, connectResponse.States);
-                                await context.Response.WriteAsync(JsonSerializer.Serialize(connectResponse)).ConfigureAwait(false);
-                                return;
-                            }
-                            // other response is invalid, igonre.
-                            return;
+                            break;
                         }
                     case UserEventRequest messageRequest:
                         {
                             var response = await hub.OnMessageReceivedAsync(messageRequest, context.RequestAborted).ConfigureAwait(false);
-                            if (response is EventErrorResponse error)
+                            // default as null is allowed.
+                            if (response != null)
                             {
-                                context.Response.StatusCode = ConvertToStatusCode(error.Code);
-                                context.Response.ContentType = Constants.ContentTypes.PlainTextContentType;
-                                await context.Response.WriteAsync(error.ErrorMessage).ConfigureAwait(false);
-                                return;
+                                SetConnectionState(ref context, messageRequest.ConnectionContext, response.States);
                             }
-                            else if (response is UserEventResponse msgResponse)
+                            if (response.Message != null)
                             {
-                                SetConnectionState(ref context, messageRequest.ConnectionContext, msgResponse.States);
-                                context.Response.ContentType = ConvertToContentType(msgResponse.DataType);
-                                var payload = msgResponse.Message.ToArray();
+                                context.Response.ContentType = ConvertToContentType(response.DataType);
+                                var payload = response.Message.ToArray();
                                 await context.Response.Body.WriteAsync(payload, 0, payload.Length).ConfigureAwait(false);
-                                return;
                             }
-                            // other response is invalid, igonre.
-                            return;
+                            break;
                         }
                     case ConnectedEventRequest connectedEvent:
                         {
                             _ = hub.OnConnectedAsync(connectedEvent).ConfigureAwait(false);
-                            return;
+                            break;
                         }
                     case DisconnectedEventRequest disconnectedEvent:
                         {
                             _ = hub.OnDisconnectedAsync(disconnectedEvent).ConfigureAwait(false);
-                            return;
+                            break;
                         }
                     default:
-                        return;
+                        break;
                 }
+                Log.SucceededToHandleRequest(_logger, serviceRequest.ConnectionContext);
             }
             catch (UnauthorizedAccessException ex)
             {
+                Log.FailedToHandleRequest(_logger, ex.Message, ex);
                 context.Response.StatusCode = StatusCodes.Status401Unauthorized;
                 await context.Response.WriteAsync(ex.Message).ConfigureAwait(false);
-                return;
+            }
+            catch (Exception ex)
+            {
+                Log.FailedToHandleRequest(_logger, ex.Message, ex);
+                // logging to service.
+                context.Response.StatusCode = StatusCodes.Status500InternalServerError;
+                await context.Response.WriteAsync(ex.Message).ConfigureAwait(false);
             }
         }
 
@@ -167,15 +159,6 @@ private static void SetConnectionState(ref HttpContext context, WebPubSubConnect
             }
         }
 
-        private static int ConvertToStatusCode(WebPubSubErrorCode errorCode) =>
-            errorCode switch
-            {
-                WebPubSubErrorCode.UserError => StatusCodes.Status400BadRequest,
-                WebPubSubErrorCode.Unauthorized => StatusCodes.Status401Unauthorized,
-                // default and server error returns 500
-                _ => StatusCodes.Status500InternalServerError
-            };
-
         private static string ConvertToContentType(MessageDataType dataType) =>
             dataType switch
             {
@@ -198,5 +181,32 @@ private THub Create<THub>() where THub : WebPubSubHub
             }
             return hub;
         }
+
+        private static class Log
+        {
+            private static readonly Action<ILogger, string, string, string, Exception> _startToHandleRequest =
+                LoggerMessage.Define<string, string, string>(LogLevel.Debug, new EventId(1, "StartToHandleRequest"), "Start to handle request, connectionId: {connectionId}, eventType: {eventType}, eventName: {eventName}");
+
+            private static readonly Action<ILogger, string, string, string, Exception> _succeededToHandleRequest =
+                LoggerMessage.Define<string, string, string>(LogLevel.Debug, new EventId(2, "SucceededToHandleRequest"), "Succeeded to handle request, connectionId: {connectionId}, eventType: {eventType}, eventName: {eventName}");
+
+            private static readonly Action<ILogger, string, Exception> _failedToHandleRequest =
+                LoggerMessage.Define<string>(LogLevel.Warning, new EventId(3, "FailedToHandleRequest"), "Handle request failed. {error}");
+
+            public static void StartToHandleRequest(ILogger logger, WebPubSubConnectionContext context)
+            {
+                _startToHandleRequest(logger, context?.ConnectionId, context?.EventType.ToString(), context?.EventName, null);
+            }
+
+            public static void SucceededToHandleRequest(ILogger logger, WebPubSubConnectionContext context)
+            {
+                _succeededToHandleRequest(logger, context?.ConnectionId, context?.EventType.ToString(), context?.EventName, null);
+            }
+
+            public static void FailedToHandleRequest(ILogger logger, string error, Exception exception)
+            {
+                _failedToHandleRequest(logger, error, exception);
+            }
+        }
     }
 }

sdk/webpubsub/Microsoft.Azure.WebPubSub.AspNetCore/src/Internal/ServiceRequestHandlerAdapter.cs

@@ -1,6 +1,5 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
 
 namespace Microsoft.Azure.WebPubSub.AspNetCore
 {