Add support for cancelling regular hub invocations from client #64098

Copilot · Oct 17, 2025

Summary

This PR implements cancellation support for regular (non-streaming) hub method invocations from the client. Previously, only streaming invocations could be cancelled by the client. Now, when a client passes a CancellationToken to InvokeAsync and cancels it, the server-side hub method will be cancelled as well.

Example Usage

Server-side hub method:

public class MyHub : Hub
{
    public async Task<string> LongRunningOperation(CancellationToken cancellationToken)
    {
        // This will be cancelled when client cancels the invocation
        await Task.Delay(TimeSpan.FromMinutes(5), cancellationToken);
        return "Completed";
    }
}

Client-side invocation:

var cts = new CancellationTokenSource();

// Start the invocation
var task = connection.InvokeAsync<string>("LongRunningOperation", cts.Token);

// Cancel it from the client
cts.Cancel();

// The server-side method will receive cancellation
await task; // Throws TaskCanceledException

Implementation Details

Client Changes

Updated HubConnection.InvokeCoreAsyncCore to send CancelInvocationMessage when the cancellation token is triggered
Uses the same pattern already established for streaming cancellations

Server Changes

HubMethodDescriptor: Removed restriction limiting CancellationToken parameters to streaming methods only
DefaultHubDispatcher: Regular invocations now register their CancellationTokenSource in ActiveRequestCancellationSources, allowing CancelInvocationMessage to cancel them
Logging: Updated log messages to be generic rather than streaming-specific

Tests

Added client test verifying CancelInvocationMessage is sent for regular invocations
Added server test with a cancelable hub method accepting CancellationToken
Updated existing test that previously verified this wasn't supported

Breaking Changes

None. This is purely additive functionality. Existing code continues to work as before.

Notes

As mentioned by @BrennanConroy in #11542 (comment), the server infrastructure was already structured to support this - it just needed to be enabled for regular invocations in addition to streams.

Warning

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- Triggering command: /home/REDACTED/work/aspnetcore/aspnetcore/.dotnet/dotnet exec --depsfile /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/bin/Microsoft.AspNetCore.SignalR.Client.Tests/Debug/net10.0/Microsoft.AspNetCore.SignalR.Client.Tests.deps.json --runtimeconfig /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/bin/Microsoft.AspNetCore.SignalR.Client.Tests/Debug/net10.0/Microsoft.AspNetCore.SignalR.Client.Tests.runtimeconfig.json /home/REDACTED/.nuget/packages/xunit.REDACTED.console/2.9.2/tools/netcoreapp2.0/xunit.console.dll /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/bin/Microsoft.AspNetCore.SignalR.Client.Tests/Debug/net10.0/Microsoft.AspNetCore.SignalR.Client.Tests.dll -noautoreporters -xml /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/TestResults/Debug/Microsoft.AspNetCore.SignalR.Client.Tests_net10.0_x64.xml -html /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/TestResults/Debug/Microsoft.AspNetCore.SignalR.Client.Tests_net10.0_x64.html -notrait Quarantined=true -nocolor (dns block)
- Triggering command: /home/REDACTED/work/aspnetcore/aspnetcore/.dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/bin/Microsoft.AspNetCore.SignalR.Client.Tests/Debug/net10.0/Microsoft.AspNetCore.SignalR.Client.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/bin/Microsoft.AspNetCore.SignalR.Client.Tests/Debug/net10.0/Microsoft.AspNetCore.SignalR.Client.Tests.deps.json /home/REDACTED/work/aspnetcore/aspnetcore/artifacts/bin/Microsoft.AspNetCore.SignalR.Client.Tests/Debug/net10.0/testhost.dll --port 43893 --endpoint 127.0.0.1:043893 --role client --parentprocessid 22550 --telemetryoptedin false (dns block)

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Original prompt

This section details on the original issue you should resolve

<issue_title>[SignalR] Possibility to cancel long running hub method from client</issue_title>
<issue_description>I´m not quit sure if this post is more of a question or a feature request.

I noticed that the InvokeAsync<TResult>(HubConnection, String, CancellationToken) method accepts a CancellationToken. As far as I understood this token only cancels the invocation (and waiting for a result, ...) on the client, while on the server side the method proceeds.
Is this correct?

If so wouldn´t it be a nice feature to allow such a cancellation? I saw that Google offers this possibility in their gRPC framework aswell:

Cancelling RPCs
Either the client or the server can cancel an RPC at any time. A cancellation terminates the RPC immediately so that no further work is done. It is not an “undo”: changes made before the cancellation will not be rolled back.

When my understanding is wrong please provide me an example on how to do a cancellation of long running hub methods from the client.</issue_description>

<agent_instructions>See comment in #11542 (comment)</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@davidfowl Today we only support cancellation for streams but there's nothing wrong with supporting this for other invocations. @BrennanConroy @anurse I don't think we do support that, but we structured the code in such a way that we could add support for it in the future. @ We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our [Triage Process](https://github.com/dotnet/aspnetcore/blob/master/docs/TriageProcess.md). @davidfowl @muzopraha What's the scenario you have with a long running hub method? @davidfowl @thorgeirk11 No updates, best to add your scenario so we have a record of what people want to use it for before we invest the time. @BrennanConroy File a new issue and show your code. @BrennanConroy CancellationToken in the hub method signature is only supported for Server to client streaming currently.

This issue is tracking adding it for other cases.</comment_new>
<comment_new>@BrennanConroy
Since this feature isn't implemented yet that method signature won't work. It's basically trying to receive a serialized CancellationToken from the client, which isn't going to work.

The cancellation token in InvokeAsync will cancel the client waiting for a server response, but it doesn't pass that info along to the server yet. That's what this issue is tracking adding support for.

public async Task UpdateChannelAsync(TPMChannels channel, CancellationToken cts = default) ->
public async Task UpdateChannelAsync(TPMChannels channel)</comment_new>
<comment_new>@davidfowl
I'll defer to @BrennanConroy here.</comment_new>
<comment_new>@BrennanConroy
Basically we would need to update the client(s) to send a CancelInvocationMessage when the cancellation token passed in to InvokeAsync is canceled.
We currently only send that message type when the client cancels a stream

aspnetcore/src/SignalR/clients/csharp/Client.Core/src/HubConnection.cs

Line 708 in 54c0cc8

    
           await SendHubMessage(_state.CurrentConnectionStateUnsynchronized, new CancelInvocationMessage(irq.InvocationId), cancellationToken: default).ConfigureAwait(false);

The server is mostly setup to handle CancelInvocationMessage

aspnetcore/src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.cs

Lines 183 to 189 in 54c0cc8

    
           case CancelInvocationMessage cancelInvocationMessage: 
        
               // Check if there is an associated active stream and cancel it if it exists. 
        
               // The cts will be removed when the streaming method completes executing 
        
               if (connection.ActiveRequestCancellationSources.TryGetValue(cancelInvocationMessage.InvocationId!, out var cts)) 
        
               { 
        
                   Log.CancelStream(_logger, cancelInvocationMessage.InvocationId!); 
        
                   cts.Cancel();

The logs would likely need to be updated since it assumes streams are the only thing that can be canceled.

We'd also need to update the logic around which hub methods can have a synthetic argument (CancellationToken)

aspnetcore/src/SignalR/server/Core/src/Internal/HubMethodDescriptor.cs

Lines 64 to 66 in 54c0cc8

    
           if (IsStreamResponse && p.ParameterType == typeof(CancellationToken)) 
        
           { 
        
               HasSyntheticArguments = true;

A massive stretch goal would be to do the same thing for client results, which would require adding synthetic argument support on the client side and sending CancelInvocationMessage from the server. That work is tracked by #44831 and shouldn't restrict this issue from being worke...

Fixes #11542

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Co-authored-by: BrennanConroy <7574801+BrennanConroy@users.noreply.github.com>

…fying comment Co-authored-by: BrennanConroy <7574801+BrennanConroy@users.noreply.github.com>

Initial plan

84205e7

Copilot AI assigned Copilot and BrennanConroy Oct 17, 2025

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dotnet-policy-service bot added the Attention: Shared Code Modified label Oct 17, 2025

BrennanConroy removed the Attention: Shared Code Modified label Oct 17, 2025

Copilot started work on behalf of BrennanConroy October 17, 2025 19:44 View session

Copilot AI and others added 3 commits October 17, 2025 19:55

Implement cancellation of regular hub invocations from client

db1c426

Co-authored-by: BrennanConroy <7574801+BrennanConroy@users.noreply.github.com>

Add tests for hub method cancellation and fix server-side registration

c618b86

Co-authored-by: BrennanConroy <7574801+BrennanConroy@users.noreply.github.com>

Address code review feedback - add null-forgiving operators and clari…

e410c32

…fying comment Co-authored-by: BrennanConroy <7574801+BrennanConroy@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add cancellation capability to long running hub methods~~ Add support for cancelling regular hub invocations from client Oct 17, 2025

Copilot AI requested a review from BrennanConroy October 17, 2025 20:11

Copilot finished work on behalf of BrennanConroy October 17, 2025 20:11

This was referenced Oct 17, 2025

Helix failure EPT_S_NOT_REGISTERED #57416

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Add support for cancelling regular hub invocations from client #64098

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Copilot AI commented Oct 17, 2025 •

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	case CancelInvocationMessage cancelInvocationMessage:
	// Check if there is an associated active stream and cancel it if it exists.
	// The cts will be removed when the streaming method completes executing
	if (connection.ActiveRequestCancellationSources.TryGetValue(cancelInvocationMessage.InvocationId!, out var cts))
	{
	Log.CancelStream(_logger, cancelInvocationMessage.InvocationId!);
	cts.Cancel();

	if (IsStreamResponse && p.ParameterType == typeof(CancellationToken))
	{
	HasSyntheticArguments = true;

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Summary

Example Usage

Implementation Details

Client Changes

Server Changes

Tests

Breaking Changes

Notes

I tried to connect to the following addresses, but was blocked by firewall rules:

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Copilot AI commented Oct 17, 2025 •

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