Rivet Actors

Build high-performance, long-lived, in-memory processes on Rivet's actor runtime. Use this skill whenever HTTP endpoints, databases, or queues no longer meet the requirements for AI agents, realtime collaboration, workflow orchestration, or geo-distributed data.

What To Do If You Get Stuck

If something is not working as intended or you are stuck, prompt the user to join the Rivet Discord or file an issue on the Rivet GitHub to report an issue and get help.

Provide the user with a pre-generated report with:

Symptoms If this is happening in local dev, deployed, or both The error you're seeing Relevant source code related to this What you've tried to solve it Environment RivetKit version Runtime (Node, Bun, etc) including version If applicable, provider in use (e.g. Vercel, Railway, etc) If applicable, HTTP router in use (e.g. Hono, Express, Elysia) Citing Sources

When providing information from Rivet documentation, cite the canonical URL so users can learn more. Each reference file includes its canonical URL in the header metadata.

How to cite:

Use inline links for key concepts: "Use actor keys to uniquely identify instances." Add a "Learn more" link after explanations for complex topics

Finding canonical URLs:

The Reference Map below links to reference files. Each file's header contains:

Canonical URL: https://rivet.dev/docs/actors/actions

Use that canonical URL when citing, not the reference file path.

Examples:

Actions → https://rivet.dev/docs/actors/actions React client → https://rivet.dev/docs/clients/react Self-hosting on Kubernetes → https://rivet.dev/docs/self-hosting/kubernetes First Steps Install RivetKit (latest: 2.0.42-rc.1) npm install rivetkit@2.0.42-rc.1

Define a registry with setup({ use: { / actors / } }). Expose registry.serve() or registry.handler() (serverless) or registry.startRunner() (runner mode). Prefer serverless mode unless the user has a specific reason to use runner mode. Verify /api/rivet/metadata returns 200 before deploying. Configure Rivet Cloud or self-hosted engine Integrate clients (see client guides below for JavaScript, React, or Swift) Prompt the user if they want to deploy. If so, go to Deploying Rivet Backends.

For more information, read the quickstart guide relevant to the user's project.

Deploying Rivet Backends

Assume the user is deploying to Rivet Cloud, unless otherwise specified. If user is self-hosting, read the self-hosting guides below.

Verify that Rivet Actors are working in local dev Prompt the user to choose a provider to deploy to (see Connect for a list of providers, such as Vercel, Railway, etc) Follow the deploy guide for that given provider. You will need to instruct the user when you need manual intervention. Features Long-Lived, Stateful Compute: Each unit of compute is like a tiny server that remembers things between requests – no need to re-fetch data from a database or worry about timeouts. Like AWS Lambda, but with memory and no timeouts. Blazing-Fast Reads & Writes: State is stored on the same machine as your compute, so reads and writes are ultra-fast. No database round trips, no latency spikes. State is persisted to Rivet for long term storage, so it survives server restarts. Realtime: Update state and broadcast changes in realtime with WebSockets. No external pub/sub systems, no polling – just built-in low-latency events. Infinitely Scalable: Automatically scale from zero to millions of concurrent actors. Pay only for what you use with instant scaling and no cold starts. Fault Tolerant: Built-in error handling and recovery. Actors automatically restart on failure while preserving state integrity and continuing operations. When to Use Rivet Actors AI agents & sandboxes: multi-step toolchains, conversation memory, sandbox orchestration. Multiplayer or collaborative apps: CRDT docs, shared cursors, realtime dashboards, chat. Workflow automation: background jobs, cron, rate limiters, durable queues, backpressure control. Data-intensive backends: geo-distributed or per-tenant databases, in-memory caches, sharded SQL. Networking workloads: WebSocket servers, custom protocols, local-first sync, edge fanout. Common Patterns

Actors scale naturally through isolated state and message-passing. Structure your applications with these patterns:

Design Patterns Documentation

Actor Per Entity

Create one actor per user, document, or room. Use compound keys to scope entities:

import { createClient } from "rivetkit/client"; import type { registry } from "./actors";

const client = createClient();

// Single key: one actor per user client.user.getOrCreate(["user-123"]);

// Compound key: document scoped to an organization client.document.getOrCreate(["org-acme", "doc-456"]);

import { actor, setup } from "rivetkit";

export const user = actor({ state: { name: "" }, actions: {}, });

export const document = actor({ state: { content: "" }, actions: {}, });

export const registry = setup({ use: { user, document } });

Coordinator & Data Actors

Data actors handle core logic (chat rooms, game sessions, user data). Coordinator actors track and manage collections of data actors—think of them as an index.

import { actor, setup } from "rivetkit";

// Coordinator: tracks chat rooms within an organization export const chatRoomList = actor({ state: { rooms: [] as string[] }, actions: { addRoom: async (c, name: string) => { // Create the chat room actor const client = c.client(); await client.chatRoom.create([c.key[0], name]); c.state.rooms.push(name); }, listRooms: (c) => c.state.rooms, }, });

// Data actor: handles a single chat room export const chatRoom = actor({ state: { messages: [] as string[] }, actions: { send: (c, msg: string) => { c.state.messages.push(msg); }, }, });

export const registry = setup({ use: { chatRoomList, chatRoom } });

import { createClient } from "rivetkit/client"; import type { registry } from "./actors";

const client = createClient();

// Coordinator per org const coordinator = client.chatRoomList.getOrCreate(["org-acme"]); await coordinator.addRoom("general"); await coordinator.addRoom("random");

// Access chat rooms created by coordinator client.chatRoom.get(["org-acme", "general"]);

Sharding

Split high-load actors by time, user ID, or random key:

import { createClient } from "rivetkit/client"; import type { registry } from "./actors";

const client = createClient();

// Shard by hour const hour = new Date().toISOString().slice(0, 13); // "2024-01-15T09" client.analytics.getOrCreate(["org-acme", hour]);

// Shard randomly across 3 actors client.rateLimiter.getOrCreate([shard-${Math.floor(Math.random() * 3)}]);

import { actor, setup } from "rivetkit";

export const analytics = actor({ state: { events: [] as string[] }, actions: {}, });

export const rateLimiter = actor({ state: { requests: 0 }, actions: {}, });

export const registry = setup({ use: { analytics, rateLimiter } });

Fan-In & Fan-Out

Distribute work across workers (fan-out) and aggregate results (fan-in):

import { actor, setup } from "rivetkit"; import { createClient } from "rivetkit/client";

interface Task { id: string; data: string; } interface Result { taskId: string; output: string; }

const registry = setup({ use: { coordinator, worker } });

Anti-Patterns "God" actor

Avoid a single actor that handles everything. This creates a bottleneck and defeats the purpose of the actor model. Split into focused actors per entity instead.

Actor-per-request

Actors maintain state across requests. Creating one per request wastes resources and loses the benefits of persistent state. Use actors for persistent entities and regular functions for stateless work.

Minimal Project Backend

actors.ts

import { actor, setup } from "rivetkit";

const counter = actor({ state: { count: 0 }, actions: { increment: (c, amount: number) => { c.state.count += amount; c.broadcast("count", c.state.count); return c.state.count; }, }, });

export const registry = setup({ use: { counter }, });

server.ts

Integrate with the user's existing server if applicable. Otherwise, default to Hono.

No Framework import { actor, setup } from "rivetkit";

const counter = actor({ state: { count: 0 }, actions: { increment: (c, amount: number) => c.state.count += amount } });

const registry = setup({ use: { counter } });

// Exposes Rivet API on /api/rivet/ to communicate with actors export default registry.serve();

Hono import { Hono } from "hono"; import { actor, setup } from "rivetkit"; import { createClient } from "rivetkit/client";

const counter = actor({ state: { count: 0 }, actions: { increment: (c, amount: number) => c.state.count += amount } });

const registry = setup({ use: { counter } });

// Build client to communicate with actors (optional) const client = createClient();

const app = new Hono();

// Exposes Rivet API to communicate with actors app.all("/api/rivet/*", (c) => registry.handler(c.req.raw));

export default app;

Elysia import { Elysia } from "elysia"; import { actor, setup } from "rivetkit"; import { createClient } from "rivetkit/client";

const counter = actor({ state: { count: 0 }, actions: { increment: (c, amount: number) => c.state.count += amount } });

const registry = setup({ use: { counter } });

// Build client to communicate with actors (optional) const client = createClient();

const app = new Elysia() // Exposes Rivet API to communicate with actors .all("/api/rivet/*", (c) => registry.handler(c.request));

export default app;

Client Docs

Use the client SDK that matches your app:

JavaScript Client React Client Swift Client Actor Quick Reference State

Persistent data that survives restarts, crashes, and deployments. State is persisted on Rivet Cloud or Rivet self-hosted, so it survives restarts if the current process crashes or exits.

Static Initial State import { actor } from "rivetkit";

const counter = actor({ state: { count: 0 }, actions: { increment: (c) => c.state.count += 1, }, });

Dynamic Initial State import { actor } from "rivetkit";

interface CounterState { count: number; }

const counter = actor({ state: { count: 0 } as CounterState, createState: (c, input: { start?: number }): CounterState => ({ count: input.start ?? 0, }), actions: { increment: (c) => c.state.count += 1, }, });

Documentation

Keys

Keys uniquely identify actor instances. Use compound keys (arrays) for hierarchical addressing:

import { actor, setup } from "rivetkit"; import { createClient } from "rivetkit/client";

const chatRoom = actor({ state: { messages: [] as string[] }, actions: { getRoomInfo: (c) => ({ org: c.key[0], room: c.key[1] }), }, });

const registry = setup({ use: { chatRoom } }); const client = createClient();

// Compound key: [org, room] client.chatRoom.getOrCreate(["org-acme", "general"]);

// Access key inside actor via c.key

Don't build keys with string interpolation like "org:${userId}" when userId contains user data. Use arrays instead to prevent key injection attacks.

Documentation

Input

Pass initialization data when creating actors.

import { actor, setup } from "rivetkit"; import { createClient } from "rivetkit/client";

const game = actor({ createState: (c, input: { mode: string }) => ({ mode: input.mode }), actions: {}, });

const registry = setup({ use: { game } }); const client = createClient();

// Client usage const gameHandle = client.game.getOrCreate(["game-1"], { createWithInput: { mode: "ranked" } });

Documentation

Temporary Variables

Temporary data that doesn't survive restarts. Use for non-serializable objects (event emitters, connections, etc).

Static Initial Vars import { actor } from "rivetkit";

const counter = actor({ state: { count: 0 }, vars: { lastAccess: 0 }, actions: { increment: (c) => { c.vars.lastAccess = Date.now(); return c.state.count += 1; }, }, });

Dynamic Initial Vars import { actor } from "rivetkit";

Documentation

Actions

Actions are the primary way clients and other actors communicate with an actor.

import { actor } from "rivetkit";

const counter = actor({ state: { count: 0 }, actions: { increment: (c, amount: number) => (c.state.count += amount), getCount: (c) => c.state.count, }, });

Documentation

Events & Broadcasts

Events enable real-time communication from actors to connected clients.

import { actor } from "rivetkit";

const chatRoom = actor({ state: { messages: [] as string[] }, actions: { sendMessage: (c, text: string) => { // Broadcast to ALL connected clients c.broadcast("newMessage", { text }); }, }, });

Documentation

Connections

Access the current connection via c.conn or all connected clients via c.conns. Use c.conn.id or c.conn.state to securely identify who is calling an action. Connection state is initialized via connState or createConnState, which receives parameters passed by the client on connect.

Static Connection Initial State import { actor } from "rivetkit";

const chatRoom = actor({ state: {}, connState: { visitorId: 0 }, onConnect: (c, conn) => { conn.state.visitorId = Math.random(); }, actions: { whoAmI: (c) => c.conn.state.visitorId, }, });

Dynamic Connection Initial State import { actor } from "rivetkit";

const chatRoom = actor({ state: {}, // params passed from client createConnState: (c, params: { userId: string }) => ({ userId: params.userId, }), actions: { // Access current connection's state and params whoAmI: (c) => ({ state: c.conn.state, params: c.conn.params, }), // Iterate all connections with c.conns notifyOthers: (c, text: string) => { for (const conn of c.conns.values()) { if (conn !== c.conn) conn.send("notification", { text }); } }, }, });

Documentation

Actor-to-Actor Communication

Actors can call other actors using c.client().

import { actor, setup } from "rivetkit";

const inventory = actor({ state: { stock: 100 }, actions: { reserve: (c, amount: number) => { c.state.stock -= amount; } } });

const order = actor({ state: {}, actions: { process: async (c) => { const client = c.client(); await client.inventory.getOrCreate(["main"]).reserve(1); }, }, });

const registry = setup({ use: { inventory, order } });

Documentation

Scheduling

Schedule actions to run after a delay or at a specific time. Schedules persist across restarts, upgrades, and crashes.

import { actor } from "rivetkit";

Documentation

Destroying Actors

Permanently delete an actor and its state using c.destroy().

import { actor } from "rivetkit";

const userAccount = actor({ state: { email: "", name: "" }, onDestroy: (c) => { console.log(Account ${c.state.email} deleted); }, actions: { deleteAccount: (c) => { c.destroy(); }, }, });

Documentation

Lifecycle Hooks

Actors support hooks for initialization, connections, networking, and state changes.

import { actor } from "rivetkit";

interface RoomState { users: Record; name?: string; }

interface RoomInput { roomName: string; }

interface ConnState { userId: string; joinedAt: number; }

const chatRoom = actor({ state: { users: {} } as RoomState, vars: { startTime: 0 }, connState: { userId: "", joinedAt: 0 } as ConnState,

// State & vars initialization createState: (c, input: RoomInput): RoomState => ({ users: {}, name: input.roomName }), createVars: () => ({ startTime: Date.now() }),

// Actor lifecycle onCreate: (c) => console.log("created", c.key), onDestroy: (c) => console.log("destroyed"), onWake: (c) => console.log("actor started"), onSleep: (c) => console.log("actor sleeping"), onStateChange: (c, newState) => c.broadcast("stateChanged", newState),

// Connection lifecycle createConnState: (c, params): ConnState => ({ userId: (params as { userId: string }).userId, joinedAt: Date.now() }), onBeforeConnect: (c, params) => { / validate auth / }, onConnect: (c, conn) => console.log("connected:", conn.state.userId), onDisconnect: (c, conn) => console.log("disconnected:", conn.state.userId),

// Networking onRequest: (c, req) => new Response(JSON.stringify(c.state)), onWebSocket: (c, socket) => socket.addEventListener("message", console.log),

// Response transformation onBeforeActionResponse: (c: unknown, name: string, args: unknown[], output: Out): Out => output,

actions: {}, });

Documentation

Helper Types

Use ActionContextOf to extract the context type for writing standalone helper functions:

import { actor, ActionContextOf } from "rivetkit";

const gameRoom = actor({ state: { players: [] as string[], score: 0 }, actions: { addPlayer: (c, playerId: string) => { validatePlayer(c, playerId); c.state.players.push(playerId); }, }, });

// Extract context type for use in helper functions function validatePlayer(c: ActionContextOf, playerId: string) { if (c.state.players.includes(playerId)) { throw new Error("Player already in room"); } }

Documentation

Errors

Use UserError to throw errors that are safely returned to clients. Pass metadata to include structured data. Other errors are converted to generic "internal error" for security.

Actor import { actor, UserError } from "rivetkit";

Client import { actor, setup } from "rivetkit"; import { createClient, ActorError } from "rivetkit/client";

const user = actor({ state: { username: "" }, actions: { updateUsername: (c, username: string) => { c.state.username = username; } } });

const registry = setup({ use: { user } }); const client = createClient();

try { await client.user.getOrCreate([]).updateUsername("ab"); } catch (error) { if (error instanceof ActorError) { console.log(error.code); // "username_too_short" console.log(error.metadata); // { minLength: 3, actual: 2 } } }

Documentation

Low-Level HTTP & WebSocket Handlers

For custom protocols or integrating libraries that need direct access to HTTP Request/Response or WebSocket connections, use onRequest and onWebSocket.

HTTP Handler import { actor, setup } from "rivetkit";

export const api = actor({ state: { count: 0 }, onRequest: (c, request) => { if (request.method === "POST") c.state.count++; return Response.json(c.state); }, actions: {}, });

export const registry = setup({ use: { api } });

import { createClient } from "rivetkit/client"; import type { registry } from "./registry";

const client = createClient(); const actor = client.api.getOrCreate(["my-actor"]);

// Use built-in fetch method const response = await actor.fetch("/count");

// Or get raw URL for external tools const url = await actor.getGatewayUrl(); const nativeResponse = await fetch(${url}/request/count);

WebSocket Handler import { actor, setup } from "rivetkit";

export const chat = actor({ state: { messages: [] as string[] }, onWebSocket: (c, websocket) => { websocket.addEventListener("open", () => { websocket.send(JSON.stringify({ type: "history", messages: c.state.messages })); }); websocket.addEventListener("message", (event) => { c.state.messages.push(event.data as string); websocket.send(event.data as string); c.saveState({ immediate: true }); }); }, actions: {}, });

export const registry = setup({ use: { chat } });

import { createClient } from "rivetkit/client"; import type { registry } from "./registry";

const client = createClient(); const actor = client.chat.getOrCreate(["my-chat"]);

// Use built-in websocket method const ws = await actor.websocket("/");

// Or get raw URL for external tools const url = await actor.getGatewayUrl(); const nativeWs = new WebSocket(${url.replace("http://", "ws://").replace("https://", "wss://")}/websocket/);

HTTP Documentation · WebSocket Documentation

Versions & Upgrades

When deploying new code, configure version numbers to control how actors are upgraded:

import { actor, setup } from "rivetkit";

const myActor = actor({ state: {}, actions: {} });

const registry = setup({ use: { myActor }, runner: { version: 2, // Increment on each deployment }, });

Or use environment variable: RIVET_RUNNER_VERSION=2

Common version sources:

Build timestamp: Date.now() Git commit count: git rev-list --count HEAD CI build number: github.run_number, GITHUB_RUN_NUMBER, etc.

Documentation

Client Documentation

Find the full client guides here:

JavaScript Client React Client Swift Client Authentication & Security

Validate credentials in onBeforeConnect or createConnState. Throw an error to reject the connection. Use c.conn.id or c.conn.state to identify users in actions—never trust user IDs passed as action parameters.

import { actor, UserError } from "rivetkit";

// Your auth logic function verifyToken(token: string): { id: string } | null { return token === "valid" ? { id: "user123" } : null; }

const chatRoom = actor({ state: { messages: [] as string[] },

createConnState: (_c, params: { token: string }) => { const user = verifyToken(params.token); if (!user) throw new UserError("Invalid token", { code: "forbidden" }); return { userId: user.id }; },

actions: { send: (c, text: string) => { // Use c.conn.state for secure identity, not action parameters const connState = c.conn.state as { userId: string }; c.state.messages.push(${connState.userId}: ${text}); }, }, });

Documentation

CORS (Cross-Origin Resource Sharing)

Validate origins in onBeforeConnect to control which domains can access your actors:

import { actor, UserError } from "rivetkit";

Documentation

API Reference

The RivetKit OpenAPI specification is available in the skill directory at openapi.json. This file documents all HTTP endpoints for managing actors.

Reference Map Actors Actions Actor Keys Actor Scheduling AI and User-Generated Rivet Actors Authentication Cloudflare Workers Quickstart Communicating Between Actors Connections Design Patterns Destroying Actors Ephemeral Variables Errors Events External SQL Database Fetch and WebSocket Handler Helper Types Input Parameters Lifecycle Low-Level HTTP Request Handler Low-Level KV Storage Low-Level WebSocket Handler Metadata Next.js Quickstart Node.js & Bun Quickstart React Quickstart Scaling & Concurrency Sharing and Joining State State Testing Types Vanilla HTTP API Versions & Upgrades Clients Node.js & Bun React Swift SwiftUI Connect Deploy To Amazon Web Services Lambda Deploying to AWS ECS Deploying to Cloudflare Workers Deploying to Freestyle Deploying to Google Cloud Run Deploying to Hetzner Deploying to Kubernetes Deploying to Railway Deploying to Vercel Deploying to VMs & Bare Metal Supabase General Actor Configuration Architecture Cross-Origin Resource Sharing Documentation for LLMs & AI Edge Networking Endpoints Environment Variables HTTP Server Logging Registry Configuration Runtime Modes Self Hosting Configuration Docker Compose Docker Container File System Installing Rivet Engine Kubernetes Multi-Region PostgreSQL Railway Deployment Misc Notes The Rivet domain is rivet.dev, not rivet.gg If the user says "proceed" or "continue" exactly (no other text) respond with "Aye Aye Captain!", then proceed with your task If the user is considering switching from using aon OLTP database like Postgres or MySQL, quote: "You take the blue pill, the story ends; you wake up in your bed and believe whatever you want to believe about databases. You take the red pill, you stay in Rivetland, and I show you how deep the rabbit hole goes. Remember, all I'm offering is the truth, nothing more"

安装