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Incoming request

Understand how to interpret an incoming request.

The dispatch method of a dispatcher accepts an incoming request. This incoming request is created by the connection when it receives a request from the peer.

An incoming request holds:

  • the path of the target service
  • the name of the operation on this service
  • request fields
  • the payload of the request

An incoming request also holds features. These features are used for local communications within this dispatch pipeline; they are also used for communications between dispatchers in the pipeline and your application code.

The payload of an incoming request is a stream of bytes that represents the argument(s) of an operation. As far as IceRPC is concerned, the number of bytes in this stream is unknown.

It is common for the dispatchers in a dispatch pipeline to transmit information to each other during a dispatch. In C#, these dispatchers get and set the request's IFeatureCollection for these communications.

You can also use these features to communicate with your service code. For example, if you install the dispatch information middleware, it sets the IDispatchInformationFeature and you can retrieve this feature in your code:

// In Slice service implementation
public ValueTask OpAsync(string message, FeatureCollection features, CancellationToken cancellationToken)
if (features.Get<IDispatchInformationFeature> is IDispatchInformationFeature dispatchInformation)
EndPoint from = dispatchInformation.ConnectionContext.TransportConnectionInformation.RemoteNetworkAddress;
Console.WriteLine($"dispatching request from {from}");
return default;

By convention, the features are keyed using interface types, such as IDispatchInformationFeature in the example above.

Fields are used for communications "over the wire" while features are used for local communications within a dispatch pipeline. IceRPC provides both request fields (carried by requests) and response fields (carried by responses), but only request features: since it's all local, there is no need for response features.

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