Legacy Streaming Examples

Archived and unsupported. This material is retained only to help migrate existing applications. There is no new Legacy release line, feature or compatibility work, or security fixes. New development must use the current functional API.

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 { } / C# class 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")]. When maintaining a legacy application which already has an application-owned concrete C# grain class, annotate that class directly. The repository’s CodeGen project is archived, non-packable source, and its retained generator does not create ordinary grain classes. For new actors, use the functional subscription operations; 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.