Legacy: Streaming Examples

Legacy Streaming Examples

Streaming examples for the original Orleans.FSharp grain authoring model.

The streaming modules remain current. This page only isolates the old grain-definition examples which previously appeared in the current guide. New actors use the functional grainContract / grainFor subscription operations.

On the classic grain { } / CodeGen path

Implicit subscriptions there are a per-grain Orleans attribute. The universal grain pattern shares a single FSharpGrainImpl class, so it cannot carry a per-grain [ImplicitStreamSubscription("namespace")]. Define the grain via Orleans.FSharp.CodeGen and annotate the generated C# class. For explicit subscriptions from any grain, use Stream.subscribe (shown above), which works with the universal pattern.

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Complete Example

open Orleans.FSharp.Runtime
open Orleans.FSharp.Streaming

// Configure
let config = siloConfig {
    useLocalhostClustering
    addMemoryStorage "Default"
    addMemoryStreams "Events"
    addBroadcastChannel "Alerts"
}

// Publish from a grain handler
let publisher =
    grain {
        defaultState ()
        handleWithContext (fun ctx state msg ->
            task {
                let streamProvider =
                    GrainContext.getService<IClusterClient> ctx
                    |> fun c -> c.GetStreamProvider("Events")
                let stream = Stream.getStream<string> streamProvider "logs" "app"
                do! Stream.publish stream $"Event: {msg}"
                return (), box ()
            })
    }

// Subscribe from client code
let streamProvider = client.GetStreamProvider("Events")
let stream = Stream.getStream<string> streamProvider "logs" "app"

let! sub = Stream.subscribe stream (fun msg ->
    task { printfn "Log: %s" msg })

// Pull-based consumption
let events = Stream.asTaskSeq stream
for event in events do
    printfn "Pulled: %s" event

Current guide

See Streaming for functional onStream and onBroadcast subscriptions.