Add retry feature

.editorconfig

@@ -0,0 +1,124 @@
+root = true
+
+# All files
+[*]
+indent_style = space
+
+# Xml files
+[*.xml]
+indent_size = 2
+
+[*.cs]
+#### Naming styles ####
+
+# Naming rules
+
+dotnet_naming_rule.private_field_should_be_private_field_naming.severity = warning
+dotnet_naming_rule.private_field_should_be_private_field_naming.symbols = private_field
+dotnet_naming_rule.private_field_should_be_private_field_naming.style = private_field_naming
+
+# Symbol specifications
+
+dotnet_naming_symbols.private_field.applicable_kinds = field
+dotnet_naming_symbols.private_field.applicable_accessibilities = private
+dotnet_naming_symbols.private_field.required_modifiers = 
+
+# Naming styles
+
+dotnet_naming_style.private_field_naming.required_prefix = _
+dotnet_naming_style.private_field_naming.required_suffix = 
+dotnet_naming_style.private_field_naming.word_separator = 
+dotnet_naming_style.private_field_naming.capitalization = camel_case
+csharp_indent_labels = one_less_than_current
+csharp_using_directive_placement = outside_namespace:silent
+csharp_prefer_simple_using_statement = true:suggestion
+csharp_prefer_braces = true:silent
+csharp_style_namespace_declarations = file_scoped:silent
+csharp_style_prefer_method_group_conversion = true:silent
+csharp_style_prefer_top_level_statements = true:silent
+csharp_style_prefer_primary_constructors = true:suggestion
+csharp_style_expression_bodied_methods = false:silent
+csharp_style_expression_bodied_constructors = false:silent
+csharp_style_expression_bodied_operators = false:silent
+csharp_style_expression_bodied_properties = true:silent
+csharp_style_expression_bodied_indexers = true:silent
+csharp_style_expression_bodied_accessors = true:silent
+csharp_style_expression_bodied_lambdas = true:silent
+csharp_style_expression_bodied_local_functions = false:silent
+csharp_space_around_binary_operators = before_and_after
+csharp_style_inlined_variable_declaration = true:suggestion
+csharp_style_allow_embedded_statements_on_same_line_experimental = true:silent
+csharp_style_allow_blank_lines_between_consecutive_braces_experimental = true:silent
+csharp_style_allow_blank_line_after_colon_in_constructor_initializer_experimental = true:silent
+csharp_style_allow_blank_line_after_token_in_conditional_expression_experimental = true:silent
+csharp_style_allow_blank_line_after_token_in_arrow_expression_clause_experimental = true:silent
+csharp_space_after_keywords_in_control_flow_statements = false
+
+[*.{cs,vb}]
+#### Naming styles ####
+
+# Naming rules
+
+dotnet_naming_rule.interface_should_be_begins_with_i.severity = suggestion
+dotnet_naming_rule.interface_should_be_begins_with_i.symbols = interface
+dotnet_naming_rule.interface_should_be_begins_with_i.style = begins_with_i
+
+dotnet_naming_rule.types_should_be_pascal_case.severity = suggestion
+dotnet_naming_rule.types_should_be_pascal_case.symbols = types
+dotnet_naming_rule.types_should_be_pascal_case.style = pascal_case
+
+dotnet_naming_rule.non_field_members_should_be_pascal_case.severity = suggestion
+dotnet_naming_rule.non_field_members_should_be_pascal_case.symbols = non_field_members
+dotnet_naming_rule.non_field_members_should_be_pascal_case.style = pascal_case
+
+# Symbol specifications
+
+dotnet_naming_symbols.interface.applicable_kinds = interface
+dotnet_naming_symbols.interface.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
+dotnet_naming_symbols.interface.required_modifiers = 
+
+dotnet_naming_symbols.types.applicable_kinds = class, struct, interface, enum
+dotnet_naming_symbols.types.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
+dotnet_naming_symbols.types.required_modifiers = 
+
+dotnet_naming_symbols.non_field_members.applicable_kinds = property, event, method
+dotnet_naming_symbols.non_field_members.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
+dotnet_naming_symbols.non_field_members.required_modifiers = 
+
+# Naming styles
+
+dotnet_naming_style.begins_with_i.required_prefix = I
+dotnet_naming_style.begins_with_i.required_suffix = 
+dotnet_naming_style.begins_with_i.word_separator = 
+dotnet_naming_style.begins_with_i.capitalization = pascal_case
+
+dotnet_naming_style.pascal_case.required_prefix = 
+dotnet_naming_style.pascal_case.required_suffix = 
+dotnet_naming_style.pascal_case.word_separator = 
+dotnet_naming_style.pascal_case.capitalization = pascal_case
+
+dotnet_naming_style.pascal_case.required_prefix = 
+dotnet_naming_style.pascal_case.required_suffix = 
+dotnet_naming_style.pascal_case.word_separator = 
+dotnet_naming_style.pascal_case.capitalization = pascal_case
+dotnet_style_operator_placement_when_wrapping = beginning_of_line
+tab_width = 4
+indent_size = 4
+end_of_line = crlf
+dotnet_style_coalesce_expression = true:suggestion
+dotnet_style_null_propagation = true:suggestion
+dotnet_style_prefer_is_null_check_over_reference_equality_method = true:suggestion
+dotnet_style_prefer_auto_properties = true:silent
+dotnet_style_object_initializer = true:suggestion
+dotnet_style_collection_initializer = true:suggestion
+dotnet_style_prefer_simplified_boolean_expressions = true:suggestion
+dotnet_style_prefer_conditional_expression_over_assignment = true:silent
+dotnet_style_prefer_conditional_expression_over_return = true:silent
+dotnet_style_explicit_tuple_names = true:suggestion
+dotnet_style_prefer_inferred_tuple_names = true:suggestion
+dotnet_style_prefer_inferred_anonymous_type_member_names = true:suggestion
+dotnet_style_prefer_compound_assignment = true:suggestion
+dotnet_style_namespace_match_folder = true:suggestion
+dotnet_style_allow_multiple_blank_lines_experimental = true:silent
+dotnet_style_allow_statement_immediately_after_block_experimental = true:silent
+insert_final_newline = true

EventBrokerSlim.sln

@@ -20,6 +20,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "docs", "docs", "{D8DD8B48-A
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{749C73FB-A73E-4794-8019-138CF561888B}"
 	ProjectSection(SolutionItems) = preProject
+		.editorconfig = .editorconfig
 		package-icon.png = package-icon.png
 	EndProjectSection
 EndProject

src/M.EventBrokerSlim/DependencyInjection/EventHandlerRegistryBuilder.cs

@@ -72,8 +72,8 @@ internal void CreateEventHandlerDescriptor<TEvent, THandler>(Guid eventHandlerKe
             Key: eventHandlerKey,
             EventType: typeof(TEvent),
             InterfaceType: typeof(IEventHandler<TEvent>),
-            Handle: async (handler, @event, ct) => await ((THandler)handler).Handle((TEvent)@event, ct),
-            OnError: async (handler, @event, exception, ct) => await ((THandler)handler).OnError(exception, (TEvent)@event, ct));
+            Handle: async (handler, @event, retryPolicy, ct) => await ((THandler)handler).Handle((TEvent)@event, retryPolicy, ct),
+            OnError: async (handler, @event, exception, retryPolicy, ct) => await ((THandler)handler).OnError(exception, (TEvent)@event, retryPolicy, ct));
 
         _eventsHandlersDescriptors.Add(descriptor);
     }
@@ -82,14 +82,14 @@ internal static EventHandlerRegistry Build(IEnumerable<EventHandlerRegistryBuild
     {
         EventBrokerBuilder? eventBrokerBuilder = null;
         List<EventHandlerDescriptor> descriptors = new();
-        foreach (var builder in builders)
+        foreach(var builder in builders)
         {
-            if (builder is EventBrokerBuilder)
+            if(builder is EventBrokerBuilder)
             {
                 eventBrokerBuilder = (EventBrokerBuilder)builder;
             }
 
-            foreach (var descriptor in builder._eventsHandlersDescriptors)
+            foreach(var descriptor in builder._eventsHandlersDescriptors)
             {
                 descriptors.Add(descriptor);
             }

src/M.EventBrokerSlim/DependencyInjection/ServiceCollectionExtensions.cs

@@ -54,7 +54,7 @@ public static IServiceCollection AddEventBroker(
 
         serviceCollection.AddSingleton(
             x => new ThreadPoolEventHandlerRunner(
-                x.GetRequiredKeyedService<Channel<object>>(eventBrokerKey).Reader,
+                x.GetRequiredKeyedService<Channel<object>>(eventBrokerKey),
                 x.GetRequiredService<IServiceScopeFactory>(),
                 x.GetRequiredService<EventHandlerRegistry>(),
                 x.GetRequiredKeyedService<CancellationTokenSource>(eventBrokerKey),

src/M.EventBrokerSlim/IEventHandler.cs

@@ -16,8 +16,9 @@ public interface IEventHandler<TEvent>
     /// Handles the event.
     /// </summary>
     /// <param name="event">An instance of <typeparamref name="TEvent"/> representing the event.</param>
+    /// <param name="retryPolicy">Provides ability to request a retry for the same event by the handler. Do not keep a reference to this instance, it may be pooled and reused.</param>
     /// <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
-    Task Handle(TEvent @event, CancellationToken cancellationToken);
+    Task Handle(TEvent @event, RetryPolicy retryPolicy, CancellationToken cancellationToken);
 
     /// <summary>
     /// Called when an unhadled exception is caught during execution.
@@ -26,6 +27,7 @@ public interface IEventHandler<TEvent>
     /// </summary>
     /// <param name="exception">The exception caught.</param>
     /// <param name="event">The event instance which handling caused the exception.</param>
+    /// <param name="retryPolicy">Provides ability to request a retry for the same event by the handler. Do not keep a reference to this instance, it may be pooled and reused.</param>
     /// <param name="cancellationToken">A cancellation token that should be used to cancel the work</param>
-    Task OnError(Exception exception, TEvent @event, CancellationToken cancellationToken);
+    Task OnError(Exception exception, TEvent @event, RetryPolicy retryPolicy, CancellationToken cancellationToken);
 }

src/M.EventBrokerSlim/Internal/EventHandlerDescriptor.cs

@@ -8,5 +8,5 @@ internal sealed record EventHandlerDescriptor(
     Guid Key,
     Type EventType,
     Type InterfaceType,
-    Func<object, object, CancellationToken, Task> Handle,
-    Func<object, object, Exception, CancellationToken, Task> OnError);
+    Func<object, object, RetryPolicy, CancellationToken, Task> Handle,
+    Func<object, object, Exception, RetryPolicy, CancellationToken, Task> OnError);

src/M.EventBrokerSlim/Internal/HandlerExecutionContext.cs

@@ -0,0 +1,93 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.ObjectPool;
+
+namespace M.EventBrokerSlim.Internal;
+
+internal class HandlerExecutionContext
+{
+    private readonly DefaultObjectPool<RetryPolicy> _retryPolicyPool;
+    private readonly SemaphoreSlim _semaphore;
+    private readonly IServiceScopeFactory _serviceScopeFactory;
+    private readonly ILogger<ThreadPoolEventHandlerRunner>? _logger;
+    private readonly DefaultObjectPool<HandlerExecutionContext> _contextObjectPool;
+    private readonly RetryQueue _retryQueue;
+
+    public HandlerExecutionContext(DefaultObjectPool<RetryPolicy> retryPolicyPool, SemaphoreSlim semaphore, IServiceScopeFactory serviceScopeFactory, ILogger<ThreadPoolEventHandlerRunner>? logger, DefaultObjectPool<HandlerExecutionContext> contextObjectPool, RetryQueue retryQueue)
+    {
+        _retryPolicyPool = retryPolicyPool;
+        _semaphore = semaphore;
+        _serviceScopeFactory = serviceScopeFactory;
+        _logger = logger;
+        _contextObjectPool = contextObjectPool;
+        _retryQueue = retryQueue;
+    }
+
+    public HandlerExecutionContext Initialize(object @event, EventHandlerDescriptor eventHandlerDescriptor, RetryDescriptor? retryDescriptor, CancellationToken cancellationToken)
+    {
+        Event = @event;
+        EventHandlerDescriptor = eventHandlerDescriptor;
+        RetryDescriptor = retryDescriptor;
+        CancellationToken = cancellationToken;
+
+        RetryPolicy = RetryDescriptor is null ? _retryPolicyPool.Get() : RetryDescriptor.RetryPolicy;
+        return this;
+    }
+
+    public void Clear()
+    {
+        Event = null;
+        EventHandlerDescriptor = null;
+        RetryDescriptor = null;
+        CancellationToken = default;
+
+        RetryPolicy = null;
+    }
+
+    public object? Event { get; private set; }
+
+    public EventHandlerDescriptor? EventHandlerDescriptor { get; private set; }
+
+    public RetryDescriptor? RetryDescriptor { get; private set; }
+
+    public CancellationToken CancellationToken { get; private set; }
+
+    public RetryPolicy? RetryPolicy { get; private set; }
+
+    public async Task CompleteAsync()
+    {
+        if(RetryPolicy!.RetryRequested)
+        {
+            RetryPolicy.NextAttempt();
+            // first retry
+            if(RetryDescriptor is null)
+            {
+                RetryDescriptor = new RetryDescriptor(Event!, EventHandlerDescriptor!, RetryPolicy);
+            }
+
+            await _retryQueue.Enqueue(RetryDescriptor).ConfigureAwait(false);
+        }
+        else
+        {
+            _retryPolicyPool.Return(RetryPolicy);
+        }
+
+        _contextObjectPool.Return(this);
+        _semaphore.Release();
+    }
+
+    public object GetService(IServiceProvider serviceProvider)
+        => serviceProvider.GetRequiredKeyedService(EventHandlerDescriptor!.InterfaceType, EventHandlerDescriptor.Key);
+
+    public IServiceScope CreateScope()
+        => _serviceScopeFactory.CreateScope();
+
+    public void LogEventHandlerResolvingError(Exception exception)
+        => _logger?.LogEventHandlerResolvingError(Event!.GetType(), exception);
+
+    public void LogUnhandledExceptionFromOnError(Type serviceType, Exception exception)
+        => _logger?.LogUnhandledExceptionFromOnError(serviceType, exception);
+}

src/M.EventBrokerSlim/Internal/HandlerExecutionContextPooledObjectPolicy.cs

@@ -0,0 +1,40 @@
+using System.Threading;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.ObjectPool;
+
+namespace M.EventBrokerSlim.Internal;
+
+internal class HandlerExecutionContextPooledObjectPolicy : IPooledObjectPolicy<HandlerExecutionContext>
+{
+    private readonly DefaultObjectPool<RetryPolicy> _retryPolicyPool;
+    private readonly SemaphoreSlim _semaphore;
+    private readonly IServiceScopeFactory _serviceScopeFactory;
+    private readonly ILogger<ThreadPoolEventHandlerRunner>? _logger;
+    private readonly RetryQueue _retryQueue;
+
+    internal HandlerExecutionContextPooledObjectPolicy(
+        DefaultObjectPool<RetryPolicy> retryPolicyPool,
+        SemaphoreSlim semaphore,
+        IServiceScopeFactory serviceScopeFactory,
+        ILogger<ThreadPoolEventHandlerRunner>? logger,
+        RetryQueue retryQueue)
+    {
+        _retryPolicyPool = retryPolicyPool;
+        _semaphore = semaphore;
+        _serviceScopeFactory = serviceScopeFactory;
+        _logger = logger;
+        _retryQueue = retryQueue;
+    }
+
+    internal DefaultObjectPool<HandlerExecutionContext>? ContextObjectPool { get; set; }
+
+    public HandlerExecutionContext Create()
+        => new HandlerExecutionContext(_retryPolicyPool, _semaphore, _serviceScopeFactory, _logger, ContextObjectPool!, _retryQueue);
+
+    public bool Return(HandlerExecutionContext obj)
+    {
+        obj.Clear();
+        return true;
+    }
+}

src/M.EventBrokerSlim/Internal/RetryDescriptor.cs

@@ -0,0 +1,3 @@
+namespace M.EventBrokerSlim.Internal;
+
+internal record RetryDescriptor(object Event, EventHandlerDescriptor EventHandlerDescriptor, RetryPolicy RetryPolicy);

src/M.EventBrokerSlim/Internal/RetryPolicyPooledObjectPolicy.cs

@@ -0,0 +1,17 @@
+using Microsoft.Extensions.ObjectPool;
+
+namespace M.EventBrokerSlim.Internal;
+
+internal class RetryPolicyPooledObjectPolicy : IPooledObjectPolicy<RetryPolicy>
+{
+    public RetryPolicy Create()
+    {
+        return new RetryPolicy();
+    }
+
+    public bool Return(RetryPolicy obj)
+    {
+        obj.Clear();
+        return true;
+    }
+}