Cloud Deployment

Cloud Deployment Overview

Learn how Trebuchet enables serverless deployment of distributed actors.

Overview

TrebuchetCloud provides the abstractions needed to deploy Swift distributed actors to serverless platforms. Instead of running a persistent server, your actors execute on-demand in response to invocations.

Architecture

┌───────────────────────────────────────────────────────────────┐
│                      Cloud Environment                        │
│  ┌─────────────────────────────────────────────────────────┐  │
│  │              CloudGateway                               │  │
│  │  ┌─────────────┐    ┌─────────────┐    ┌────────────┐   │  │
│  │  │ UserService │    │  GameRoom   │    │   Lobby    │   │  │
│  │  └─────────────┘    └─────────────┘    └────────────┘   │  │
│  └─────────────────────────────────────────────────────────┘  │
│                              ↓                                │
│  ┌──────────────┐  ┌──────────────┐  ┌───────────────────┐    │
│  │  StateStore  │  │   Registry   │  │   HTTP Endpoint   │    │
│  │ (DynamoDB)   │  │  (CloudMap)  │  │  (API Gateway)    │    │
│  └──────────────┘  └──────────────┘  └───────────────────┘    │
└───────────────────────────────────────────────────────────────┘

Key Components

CloudGateway

The CloudGateway is the entry point for hosting actors in cloud environments. It handles:

• Actor registration and exposure
• Incoming invocation routing
• State persistence coordination
• Service registry integration

import TrebuchetCloud

let gateway = CloudGateway(configuration: .init(
    host: "0.0.0.0",
    port: 8080,
    stateStore: myStateStore,
    registry: myRegistry
))

try await gateway.expose(myActor, as: "my-actor")
try await gateway.run()

CloudProvider Protocol

The CloudProvider protocol abstracts cloud platform specifics:

public protocol CloudProvider: Sendable {
    associatedtype FunctionConfig: Sendable
    associatedtype DeploymentResult: CloudDeployment

    func deploy<A: DistributedActor>(
        _ actorType: A.Type,
        as actorID: String,
        config: FunctionConfig,
        factory: @Sendable (TrebuchetActorSystem) -> A
    ) async throws -> DeploymentResult

    func transport(for deployment: DeploymentResult) async throws -> any TrebuchetTransport
}

Implementations:

• AWSProvider: AWS Lambda + API Gateway
• GCPProvider: Google Cloud Functions
• AzureProvider: Azure Functions
• LocalProvider: Local development

ServiceRegistry

The ServiceRegistry protocol enables actor discovery:

public protocol ServiceRegistry: Sendable {
    func register(
        actorID: String,
        endpoint: CloudEndpoint,
        metadata: [String: String],
        ttl: Duration?
    ) async throws

    func resolve(actorID: String) async throws -> CloudEndpoint?

    func deregister(actorID: String) async throws
}

Implementations:

• CloudMapRegistry: AWS Cloud Map
• InMemoryRegistry: Local development

ActorStateStore

The ActorStateStore protocol provides state persistence:

public protocol ActorStateStore: Sendable {
    func load<State: Codable & Sendable>(
        for actorID: String,
        as type: State.Type
    ) async throws -> State?

    func save<State: Codable & Sendable>(
        _ state: State,
        for actorID: String
    ) async throws

    func delete(for actorID: String) async throws
}

Implementations:

• DynamoDBStateStore: AWS DynamoDB
• PostgreSQLStateStore: PostgreSQL
• InMemoryStateStore: Local development

Stateful Actors

Actors that need persistent state implement StatefulActor:

import TrebuchetCloud

@Trebuchet
distributed actor ShoppingCart: StatefulActor {
    typealias PersistentState = CartState

    let stateStore: ActorStateStore
    var persistentState = CartState()

    init(actorSystem: TrebuchetActorSystem, stateStore: ActorStateStore) async throws {
        self.actorSystem = actorSystem
        self.stateStore = stateStore
        try await loadState(from: stateStore)
    }

    distributed func addItem(_ item: Item) async throws -> CartState {
        persistentState.items.append(item)
        try await saveState(to: stateStore)
        return persistentState
    }

    func loadState(from store: any ActorStateStore) async throws {
        if let state = try await store.load(for: id.id, as: CartState.self) {
            persistentState = state
        }
    }

    func saveState(to store: any ActorStateStore) async throws {
        try await store.save(persistentState, for: id.id)
    }
}

struct CartState: Codable, Sendable {
    var items: [Item] = []
}

Actor-to-Actor Communication

Actors deployed to cloud functions can discover and invoke each other in two ways:

1. Via Transport (Client Resolution)

import TrebuchetCloud
import TrebuchetAWS

// From within an actor running in Lambda
@Trebuchet
distributed actor GameRoom {
    let client: TrebuchetCloudClient

    distributed func notifyLobby() async throws {
        // Resolve another actor via service registry
        let lobby = try await client.resolve(Lobby.self, id: "lobby")

        // Invoke it (triggers another Lambda invocation)
        try await lobby.onGameStarted(roomID: id.id)
    }
}

2. Via CloudGateway.process() (Direct Invocation)

Added in v0.3.0 - For programmatic actor invocation without HTTP overhead:

import TrebuchetCloud

let gateway = CloudGateway(configuration: .init(
    stateStore: stateStore,
    registry: registry
))

// Register actors
try await gateway.expose(myActor, as: "my-actor")

// Programmatic invocation (actor-to-actor, no HTTP)
let envelope = InvocationEnvelope(
    callID: UUID(),
    actorID: TrebuchetActorID(id: "my-actor"),
    targetIdentifier: "myMethod(param:)",
    genericSubstitutions: [],
    arguments: [try JSONEncoder().encode("value")]
)

let response = await gateway.process(envelope)

Use cases:

• Lambda-to-Lambda communication without API Gateway overhead
• Local actor-to-actor calls in same process
• Testing actor methods programmatically
• Building custom transport layers

Local Development

For local development, use the in-memory implementations:

import TrebuchetCloud

let gateway = CloudGateway.development(host: "localhost", port: 8080)

This creates a gateway with:

• InMemoryStateStore for state persistence
• InMemoryRegistry for service discovery
• Local HTTP server on specified port

Local Development Example

import Trebuchet
import TrebuchetCloud

@main
struct DevServer {
    static func main() async throws {
        // Create local gateway
        let gateway = CloudGateway.development(host: "localhost", port: 8080)

        // Create actors
        let room = GameRoom(actorSystem: gateway.system)
        let lobby = Lobby(actorSystem: gateway.system)

        // Expose actors
        try await gateway.expose(room, as: "game-room")
        try await gateway.expose(lobby, as: "lobby")

        print("Local development server running on http://localhost:8080")
        try await gateway.run()
    }
}

Deployment Workflow

1. Define actors with @Trebuchet macro
2. Configure deployment in trebuchet.yaml
3. Deploy with CLI: trebuchet deploy --provider aws
4. Invoke via HTTP endpoint or from other actors

Configuration File

Create a trebuchet.yaml to configure deployment:

name: my-game-server
version: "1"

defaults:
  provider: aws
  region: us-east-1
  memory: 512
  timeout: 30

actors:
  GameRoom:
    memory: 1024
    stateful: true
  Lobby:
    memory: 256

state:
  type: dynamodb

discovery:
  type: cloudmap
  namespace: my-game

Middleware Support

CloudGateway supports middleware for cross-cutting concerns:

import TrebuchetCloud
import TrebuchetSecurity
import TrebuchetObservability

let gateway = CloudGateway(configuration: .init(
    middlewares: [
        ValidationMiddleware(...),      // Request validation
        AuthenticationMiddleware(...),  // Authentication
        AuthorizationMiddleware(...),   // Authorization
        RateLimitingMiddleware(...),    // Rate limiting
        TracingMiddleware(...)          // Distributed tracing
    ],
    stateStore: stateStore,
    registry: registry
))

Benefits of Serverless Deployment

Cost Efficiency

• Pay only for actual invocations
• No cost for idle time
• Automatic scaling to zero

Scalability

• Automatic horizontal scaling
• Handle traffic spikes effortlessly
• No capacity planning needed

Operational Simplicity

• No server management
• Automatic patching and updates
• Built-in high availability

Developer Experience

• Deploy with single command
• Focus on business logic
• Infrastructure as code

Best Practices

Minimize Cold Start Latency

• Use provisioned concurrency for critical paths
• Keep dependencies minimal
• Use ARM64 for 20% faster cold starts

State Management

• Use DynamoDB for shared state
• Cache frequently accessed data
• Implement proper TTL for cleanup

Error Handling

• Implement retry logic for transient failures
• Use dead-letter queues for failed invocations
• Monitor error rates with CloudWatch

Testing

• Test locally with development gateway
• Use integration tests with real cloud resources
• Implement canary deployments

See Also

• AWS Lambda deployment guide for AWS-specific setup
• CLI guide for deployment commands
• Security guide for authentication and authorization
• Observability guide for logging and metrics

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