ctrl-c doesn't cancel server on mac and linux

[mbcrawfo]

Describe the bug
After sending Ctrl-C to the console app, the server logs indicate that it is shutting down, but the process never exits requiring it to be killed.

Edit: I'm experiencing this on MacOS with SDK 9.0.100. I haven't tried Windows or .Net 8.

To Reproduce

1. dotnet new console
2. dotnet add package ModelContextProtocol --prerelease
3. dotnet add package Microsoft.Extensions.Hosting
4. Copy code below into Program.cs and dotnet run

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

var builder = Host.CreateApplicationBuilder(args);
builder.Logging.AddConsole(options => options.LogToStandardErrorThreshold = LogLevel.Trace);
builder.Services.AddMcpServer().WithStdioServerTransport();
await builder.Build().RunAsync();

Expected behavior

The app should completely shut down and exit after receiving a Ctrl-C signal.

Logs

info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[728055718]
      Transport entering read messages loop for Server (stream) (mcp-server-shutdown)
info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[625848173]
      Transport waiting for message for Server (stream) (mcp-server-shutdown)
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]
      Content root path: /Users/michael/Projects/mcp-server-shutdown
info: Microsoft.Hosting.Lifetime[0]
      Application is shutting down...
info: ModelContextProtocol.Server.McpServer[52599573]
      Endpoint message processing cancelled for Server (mcp-server-shutdown 1.0.0.0)
info: ModelContextProtocol.Server.McpServer[471153486]
      Cleaning up endpoint Server (mcp-server-shutdown 1.0.0.0)
info: ModelContextProtocol.Server.McpServer[883836513]
      Endpoint cleaned up for Server (mcp-server-shutdown 1.0.0.0)
info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[156234308]
      Transport cleaning up for Server (stream) (mcp-server-shutdown)

[StefH]

I think I also encountered this, so for now I'm using this workaround:

var host = builder.Build();

var cts = new CancellationTokenSource();

Console.CancelKeyPress += (sender, e) =>
{
    e.Cancel = true;
    cts.Cancel();
};

AppDomain.CurrentDomain.ProcessExit += (sender, e) =>
{
    cts.Cancel();
};

return host.RunAsync(cts.Token);

[stephentoub]

I'm having trouble reproing this.

I get this output:

info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[728055718]
      Transport entering read messages loop for Server (stream) (TestServerWithHosting)
info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[625848173]
      Transport waiting for message for Server (stream) (TestServerWithHosting)
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]
      Content root path: D:\repos\mcp\artifacts\bin\TestServerWithHosting\Debug\net9.0

and then the moment I ctrl+C on the console for the server process, I get this:

info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[815295334]
      Transport end of stream for Server (stream) (TestServerWithHosting)
info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[964850216]
      Transport exiting read messages loop for Server (stream) (TestServerWithHosting)
info: Microsoft.Hosting.Lifetime[0]
      Application is shutting down...
info: ModelContextProtocol.Server.McpServer[471153486]
      Cleaning up endpoint Server (TestServerWithHosting 1.0.0.0)
info: ModelContextProtocol.Server.McpServer[883836513]
      Endpoint cleaned up for Server (TestServerWithHosting 1.0.0.0)
info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[156234308]
      Transport cleaning up for Server (stream) (TestServerWithHosting)
info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[2127575032]
      Transport read task cleaned up for Server (stream) (TestServerWithHosting)
info: ModelContextProtocol.Protocol.Transport.StdioServerTransport[557936653]
      Transport cleaned up for Server (stream) (TestServerWithHosting)

D:\repos\mcp\artifacts\bin\TestServerWithHosting\Debug\net9.0\TestServerWithHosting.exe (process 21172) exited with code 0 (0x0).

[mbcrawfo]

@stephentoub It seems like it doesn't affect Windows. I tested on Win 10 with SDK 9.0.202 and did not have see the problem. On my Mac, the workaround suggested above also does not work.

[mbcrawfo]

FWIW I tried pulling the latest from main and building locally (on the Mac) to see if #226 would fix the issue, unfortunately it doesn't. This is the output from TestServerWithHosting:

 ~/Projects/mcp-csharp-sdk/artifacts/bin/TestServerWithHosting/Release/net9.0
[main|✔]
13:11 $ dotnet TestServerWithHosting.dll
[13:12:33 INF] Starting server...
[13:12:33 DBG] Hosting starting
[13:12:33 INF] Transport entering read messages loop for Server (stream) (TestServerWithHosting)
[13:12:33 INF] Transport waiting for message for Server (stream) (TestServerWithHosting)
[13:12:33 INF] Application started. Press Ctrl+C to shut down.
[13:12:33 INF] Hosting environment: Production
[13:12:33 INF] Content root path: /Users/michael/Projects/mcp-csharp-sdk/artifacts/bin/TestServerWithHosting/Release/net9.0
[13:12:33 DBG] Hosting started
[13:12:40 INF] Application is shutting down...
[13:12:40 DBG] Hosting stopping
[13:12:40 INF] Endpoint message processing cancelled for Server (TestServerWithHosting 1.0.0.0)
[13:12:40 INF] Cleaning up endpoint Server (TestServerWithHosting 1.0.0.0)
[13:12:40 INF] Endpoint cleaned up for Server (TestServerWithHosting 1.0.0.0)
[13:12:40 DBG] Hosting stopped
[13:12:40 INF] Transport cleaning up for Server (stream) (TestServerWithHosting)
[13:12:40 DBG] Transport waiting for read task for Server (stream) (TestServerWithHosting)

[mbcrawfo]

Tried my app in docker today and this also affects linux containers - prevents the container from shutting down.

[johnkors]

Yeah, I get the same experience. It feels like there is no cancellation token checking during shutdown.

MacOS + dotnet9 here.