Client Configuration

Guide to the clientConfig { } computation expression.

What you’ll learn

• How to configure an Orleans client to connect to a silo
• Clustering modes: localhost, static gateways
• TLS for secure client connections
• Custom DI services on the client

Overview

The clientConfig { } CE builds a ClientConfig record. Apply it to a host or build it directly:

open Orleans.FSharp.Runtime

let config = clientConfig {
    useLocalhostClustering
}

// Option 1: Apply to a HostApplicationBuilder
let builder = HostApplicationBuilder()
ClientConfig.applyToHost config builder

// Option 2: Build directly (creates a host and returns the client)
let host, client = ClientConfig.build config
host.StartAsync().GetAwaiter().GetResult()

---

Clustering

Localhost

Connect to a single local silo for development:

clientConfig { useLocalhostClustering }

Static gateways

Connect to known silo endpoints:

clientConfig {
    useStaticClustering [ "10.0.0.1:30000"; "10.0.0.2:30000" ]
}

Each endpoint must be in "host:port" format.

---

Cluster Identity

clientConfig {
    useLocalhostClustering
    clusterId "my-cluster"
    serviceId "my-service"
}

The clusterId and serviceId must match the silo configuration.

---

Gateway Options

Refresh period

How often the client refreshes its list of available gateways:

clientConfig {
    useLocalhostClustering
    gatewayListRefreshPeriod (TimeSpan.FromSeconds 30.)
}

Preferred gateway

Set the preferred gateway index for client connections:

clientConfig {
    useLocalhostClustering
    preferredGatewayIndex 0
}

---

Streaming

In-memory streams

clientConfig {
    useLocalhostClustering
    addMemoryStreams "StreamProvider"
}

---

TLS

TLS by subject name

clientConfig {
    useLocalhostClustering
    useTls "CN=my-client-cert"
}

TLS with certificate

let cert = new X509Certificate2("path/to/cert.pfx", "password")

clientConfig {
    useLocalhostClustering
    useTlsWithCertificate cert
}

Mutual TLS

clientConfig {
    useLocalhostClustering
    useMutualTls "CN=my-client-cert"
}

---

Serialization

Select one generalized-serialization policy. AddFunctionalGrainClient installs the binary functional default; configure an explicit policy only when this client should choose a different codec for ungenerated application types:

let serialization =
    FSharpSerialization.Binary
    |> FSharpSerialization.forUnsupportedTypes FSharpSerialization.Json

clientConfig {
    useLocalhostClustering
    useFSharpSerialization serialization
}

The client and silo must select the same policy. Use useFSharpJsonSerialization when JSON should be the primary generalized codec. See Serialization.

---

Custom DI Services

Register services on the client’s DI container:

clientConfig {
    useLocalhostClustering
    configureServices (fun services ->
        services.AddSingleton<IMyService, MyService>() |> ignore)
}

---

Calling a functional grain from a client-only process

clientConfig { } configures the connection; the functional transport is installed separately, on the IClientBuilder, with AddFunctionalGrainClient(). A process that also hosts the definition needs nothing extra – AddFunctionalGrain on the silo builder installs the client transport too.

open Orleans.FSharp

builder.UseOrleansClient(fun clientBuilder ->
    clientBuilder.AddFunctionalGrainClient() |> ignore)
|> ignore

// Then bind the typed API record against the connected client.
let api = CounterApi.ref client "my-counter"

The call is idempotent, and it fails at configuration time with a diagnostic naming IGrainReferenceActivatorProvider if it runs before Orleans has installed its own reference activators. See Functional Grain Runtime.

---

Complete Example

open System
open System.Threading.Tasks
open Orleans
open Orleans.FSharp
open Orleans.FSharp.Runtime
open Microsoft.Extensions.DependencyInjection
open Microsoft.Extensions.Hosting

type CounterActor = private CounterActor of unit

[<NoEquality; NoComparison>]
type CounterApi = { increment: unit -> Task<int> }

[<RequireQualifiedAccess>]
module CounterApi =
    let contract =
        grainContract<CounterActor, string, CounterApi> {
            grainType "counter"
            version 1
            stringKey
        }

    let ref = FunctionalGrain.ref contract

let config = clientConfig {
    useStaticClustering [ "10.0.0.1:30000"; "10.0.0.2:30000" ]
    clusterId "production"
    serviceId "my-app"
    useMutualTls "CN=orleans-client"
    gatewayListRefreshPeriod (TimeSpan.FromSeconds 30.)
    addMemoryStreams "Events"
}

let builder = HostApplicationBuilder()
ClientConfig.applyToHost config builder
builder.UseOrleansClient(fun clientBuilder ->
    clientBuilder.AddFunctionalGrainClient() |> ignore)
|> ignore

let host = builder.Build()
host.Start()
let client = host.Services.GetRequiredService<IClusterClient>()

let counter = CounterApi.ref client "my-counter"
let result = counter.increment().GetAwaiter().GetResult()

Next steps

• Silo Configuration – configure the silo that this client connects to
• Streaming – publish and subscribe to streams from the client
• Security – TLS and mTLS in depth