Orleans JournaledGrain sample #7029

egil · 2025-03-14T12:52:58Z

This sample aims to showcase different ways to use JournaledGrains.

Features:

Uses Aspire with a mix of persistent storage and session storage. Grain state is persistent across runs, clustering is not.
Uses Blazor Interactive Server for frontend bits
Uses JournaledGrain with Log storage
Uses grain observers to auto update Blazor UI
Allow users to see previous versions of todo lists
Use state-based storage for todo list registry grain to showcase that

Todo:

JournaledGrain with Custom storage

egil · 2025-03-14T12:54:43Z

@ReubenBond here is a draft of the sample. Still things I want to add, but would like to get input on how things are looking before I wonder off in a wrong direction.

orleans/JournaledTodoList/JournaledTodoList.WebApp/Grains/TodoListRegistryGrain.cs

egil · 2025-03-17T18:00:34Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Program.cs

+builder.AddKeyedAzureTableClient("clustering");
+builder.AddKeyedAzureBlobClient("grain-state");
+builder.UseOrleans(siloBuilder =>
+{
+    siloBuilder.AddLogStorageBasedLogConsistencyProviderAsDefault();
+    siloBuilder.AddStateStorageBasedLogConsistencyProvider(name: Constants.StateStorageProviderName);
+});


With this set up, the log consistency providers are using the grain state as storage, in this case, blob storage. When the log-based providers save state, does it just save the added/raised event(s), or does it save all in one go? That is, if there are 1000 events, will they all be serialized and save to blob storage or just the new events?

…grain to be state-based journaled

Copilot

Pull request overview

This PR introduces a new Orleans sample demonstrating JournaledGrain functionality with event sourcing. The sample implements a todo list application using Blazor Interactive Server, Orleans JournaledGrains for state management, and Aspire for orchestration. It showcases both log-based and state-based consistency providers, grain observers for real-time UI updates, and the ability to view historical versions of todo lists.

Changes:

Added complete Orleans JournaledGrain sample with Aspire orchestration
Implemented event-sourced todo list grains with historical versioning capability
Created Blazor Interactive Server UI with real-time updates via grain observers

Reviewed changes

Copilot reviewed 42 out of 42 changed files in this pull request and generated 19 comments.

Show a summary per file

File	Description
JournaledTodoList.slnx	Solution file defining the three-project structure
JournaledTodoList.AppHost/*	Aspire AppHost configuration with Azure Storage emulators for clustering and persistence
JournaledTodoList.ServiceDefaults/*	Shared service defaults for OpenTelemetry, health checks, and resilience
JournaledTodoList.WebApp/Program.cs	Application entry point configuring Orleans, Blazor, and services
JournaledTodoList.WebApp/Grains/*	Grain implementations and interfaces for todo lists with event sourcing
JournaledTodoList.WebApp/Grains/Events/*	Event definitions for todo list operations
JournaledTodoList.WebApp/Services/TodoListService.cs	Service layer for grain interaction and observer subscriptions
JournaledTodoList.WebApp/Components/*	Blazor components for UI including pages and layouts
JournaledTodoList.WebApp/wwwroot/app.css	Application-specific CSS styles
Configuration files	Standard appsettings and launch settings for ASP.NET Core

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Copilot · 2026-01-21T21:27:40Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Components/Pages/TodoListPage.razor.cs

+    protected override async Task OnParametersSetAsync()
+    {
+        if (todoList?.Name != ListId)
+        {
+            currentViewTimestamp = null;
+            todoList = null;
+            await LoadTodoList();
+        }


This comparison checks if todoList?.Name differs from ListId to determine if the list has changed. However, todoList.Name should contain the display name (once bug with GetTodoListAsync is fixed), while ListId is the normalized ID used as the grain key. These will typically be different strings even for the same list. Consider storing and comparing an ID field in TodoList, or comparing against a stored previous ListId value.

Copilot · 2026-01-21T21:27:40Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Grains/TodoListGrain.cs

+        var list = new TodoList(
+            Name: this.GetPrimaryKeyString(),
+            Items: State.Items.Values.OrderBy(x => x.Id).ToImmutableArray(),
+            Timestamp: State.Timestamp);


The GetTodoListAsync method sets Name to this.GetPrimaryKeyString() (the grain ID) rather than State.Name (the display name from the projection). This means the display name set via SetNameAsync is ignored, and the TodoList always shows the normalized ID instead of the user-friendly name. The Name parameter should be set to State.Name to reflect the actual list name.

Copilot · 2026-01-21T21:27:40Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Grains/TodoListGrain.cs

+            ? new TodoList(
+                Name: this.GetPrimaryKeyString(),
+                Items: historicalProjection.Items.Values.OrderBy(x => x.Id).ToImmutableArray(),
+                Timestamp: historicalProjection.Timestamp)


Similar to GetTodoListAsync, this method sets Name to this.GetPrimaryKeyString() instead of historicalProjection.Name. This means historical views won't show the correct display name that was set at that point in time. The Name parameter should be set to historicalProjection.Name to show the name as it was at that timestamp.

Copilot · 2026-01-21T21:27:41Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Constants.cs

+public static class Constants
+{
+    public const string StateStorageProviderName = "StateStorage";
+
+    public const string TodoListRegistryId = "registry";


The Constants class is defined in the global namespace instead of being in the JournaledTodoList.WebApp namespace like other files in the project. This is inconsistent with the project's namespace structure and could lead to naming conflicts. The class should be moved into the appropriate namespace.

Suggested change

public static class Constants

{

public const string StateStorageProviderName = "StateStorage";

public const string TodoListRegistryId = "registry";

namespace JournaledTodoList.WebApp

{

public static class Constants

{

public const string StateStorageProviderName = "StateStorage";

public const string TodoListRegistryId = "registry";

}

Copilot · 2026-01-21T21:27:41Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Grains/TodoListGrain.cs

+    public async Task<TodoList> GetTodoListAsync()
+    {
+        var list = new TodoList(
+            Name: this.GetPrimaryKeyString(),
+            Items: State.Items.Values.OrderBy(x => x.Id).ToImmutableArray(),
+            Timestamp: State.Timestamp);
+
+        return list;
+    }


The GetTodoListAsync method is declared as async but doesn't use await and simply returns a Task. Consider removing the async modifier and using Task.FromResult instead to avoid unnecessary async state machine overhead.

Copilot · 2026-01-21T21:27:43Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Grains/TodoListRegistryGrain.cs

+    public Task Subscribe(ITodoListRegistryObserver observer)
+    {
+        observers.Subscribe(observer, observer);
+        observer.OnTodoListsChanged(State.TodoLists);
+        return Task.CompletedTask;


The Subscribe method calls observer.OnTodoListsChanged synchronously without awaiting it. Since OnTodoListsChanged returns a Task, this call should be awaited to ensure the initial notification completes before the Subscribe method returns. This could lead to race conditions where the component isn't properly initialized before other operations occur.

Copilot · 2026-01-21T21:27:44Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/wwwroot/app.css

+h1:focus {
+    outline: none;
+}


Removing the outline on focused h1 elements (outline: none) creates an accessibility issue. Users who navigate with keyboards rely on focus indicators to know where they are on the page. If removing the default outline is necessary for design reasons, replace it with an alternative focus indicator that meets WCAG contrast requirements.

Copilot · 2026-01-21T21:27:44Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Grains/TodoListGrain.cs

+    public async Task AddTodoItemAsync(string title)
+    {
+        var evt = new TodoItemAdded(
+            Version,
+            DateTimeOffset.UtcNow,
+            title);


The TodoItemAdded event is being constructed with Version as the ItemId parameter, but Version represents the grain's event version number, not the item ID. This will cause incorrect item IDs to be assigned (0, 1, 2, etc. based on event version). The item ID should be generated differently, such as by tracking a counter in the TodoListProjection state or using a different strategy to ensure unique item IDs.

Copilot · 2026-01-21T21:27:44Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Components/Pages/TodoListPage.razor.cs

+
+    private async Task ViewAtTimestamp(DateTimeOffset timestamp)
+    {
+        if (timestamp == history[^1].Timestamp)


The method accesses history[^1] without checking if the history array is empty. If ViewAtTimestamp is somehow called when history is empty or default, this will throw an IndexOutOfRangeException. Consider adding a guard check for history.IsDefaultOrEmpty before accessing the array.

Copilot · 2026-01-21T21:27:44Z

orleans/JournaledTodoList/JournaledTodoList.WebApp/Components/Pages/TodoListPage.razor

+                <div class="alert alert-warning" role="alert">
+                    <strong>Viewing historical version</strong>
+                    <span>as of @currentViewTimestamp.Value.ToLocalTime().ToString("g").</span>
+                    <a @onclick:preventDefault @onclick:stopPropagation @onclick="ReturnToCurrentVersion" href="#" class="link-offset-2">To current version</a>.


The link text "To current version" is grammatically incomplete. It should be "Return to current version" or "Back to current version" to form a complete sentence or clear action.

Suggested change

<a @onclick:preventDefault @onclick:stopPropagation @onclick="ReturnToCurrentVersion" href="#" class="link-offset-2">To current version</a>.

<a @onclick:preventDefault @onclick:stopPropagation @onclick="ReturnToCurrentVersion" href="#" class="link-offset-2">Return to current version</a>.

dotnet-policy-service bot added the community-contribution label Mar 14, 2025

egil commented Mar 17, 2025

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orleans/JournaledTodoList/JournaledTodoList.WebApp/Grains/TodoListRegistryGrain.cs Show resolved Hide resolved

egil commented Mar 17, 2025

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egil marked this pull request as ready for review March 17, 2025 18:00

egil requested a review from a team as a code owner March 17, 2025 18:00

ReubenBond self-assigned this Mar 17, 2025

egil and others added 8 commits January 21, 2026 13:03

Orleans JournaledGrain sample

2023916

Add timestamp to projection type

34fb307

Ensure projection has been materialized before returning list

e6397c4

Add support for navigating a todo lists history

71bc111

Allow todo lists to have different names than id's - change registry …

634bdfc

…grain to be state-based journaled

Introduce constant for todo list registry id

00d5f89

RefreshNow is not needed when OnActivateAsync is not overridden

efb88dc

Update to .NET 10, Orleans 10, Aspire 13.1.0

d044c5c

Copilot AI review requested due to automatic review settings January 21, 2026 21:16

ReubenBond force-pushed the orleans/journaled-grain-sample branch from 90ba44e to d044c5c Compare January 21, 2026 21:16

ReubenBond approved these changes Jan 21, 2026

View reviewed changes

ReubenBond enabled auto-merge (squash) January 21, 2026 21:16

ReubenBond merged commit 91b9946 into dotnet:main Jan 21, 2026
3 checks passed

Copilot started reviewing on behalf of ReubenBond January 21, 2026 21:17 View session

Copilot AI reviewed Jan 21, 2026

View reviewed changes

	<a @onclick:preventDefault @onclick:stopPropagation @onclick="ReturnToCurrentVersion" href="#" class="link-offset-2">To current version</a>.
	<a @onclick:preventDefault @onclick:stopPropagation @onclick="ReturnToCurrentVersion" href="#" class="link-offset-2">Return to current version</a>.

Orleans JournaledGrain sample #7029

Orleans JournaledGrain sample #7029

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egil commented Mar 14, 2025 •

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