One-way requests

Grains perform asynchronous request execution, requiring all grain interface methods to return an asynchronous type, like Task. Awaiting the completion of a task returned from a grain call notifies the caller that the request has finished, allowing the caller to handle any exceptions or receive return values. Orleans also supports one-way requests, enabling callers to notify a grain about an event without expecting exceptions or completion signals.

One-way requests return to the caller immediately and don't signal failure or completion. A one-way request doesn't even guarantee the callee received the request. The primary benefit of one-way requests is that they save messaging costs associated with sending a response back to the caller and can therefore improve performance in some specialized cases. One-way requests are an advanced performance feature. Use them with care and only when you determine that a one-way request is beneficial. We recommend preferring regular bidirectional requests, which signal completion and propagate errors back to callers.

You can make a request one-way by marking the grain interface method with the OneWayAttribute, like this:

public interface IOneWayGrain : IGrainWithGuidKey
{
    [OneWay]
    Task Notify(MyData data);
}

One-way requests must return either Task or ValueTask. They must not return generic variants of those types (Task<TResult> and ValueTask<TResult>).