---
title: "TypeScript Workers"
description: "This page shows how to start a TypeScript Worker. It lists the TypeScript names for the"
canonical_url: "https://docs.superdurable.io/reference/typescript/workers/"
source: "docs/reference/typescript/workers.mdx"
locale: "en"
---

# TypeScript Workers

This page shows how to start a TypeScript Worker. It lists the TypeScript names for the
Worker settings and diagnostics. The
[Workers and the task queue](https://docs.superdurable.io/reference/server/workers.md) page describes their
behavior for every SDK.

## Start a Worker

This example serves a Greeting Flow through a pull Worker. Its Step stores a
greeting, and the greeting RPC reads it. The Worker allows eight concurrent tasks
and keeps one slot for RPCs. See the [TypeScript SDK README](https://github.com/superdurable/dex/blob/main/sdk-typescript/README.md#workers) for
startup details.

```typescript
export async function startPullGreeting(
  cache: BlobCache,
  serverAddress: string,
): Promise<{ flow: GreetingFlow; worker: Worker; client: Client }> {
  const flow = new GreetingFlow();
  const registry = new Registry([flow]);
  const worker = new Worker(registry, cache, {
    serverAddress,
    pull: {
      maxConcurrentTasks: 8,
      // Keep one slot for RPCs so Flows stay responsive.
      reservedRpcTasks: 1,
    },
  });
  try {
    await worker.start();
    await worker.waitPullRegistered({ timeoutMs: 30_000 });
  } catch (failure) {
    try {
      await worker.close();
    } catch (cleanupFailure) {
      throw new AggregateError([failure, cleanupFailure], "pull Worker startup and cleanup failed");
    }
    throw failure;
  }
  const client = new Client(registry, cache, { serverAddress });
  return { flow, worker, client };
}

export async function stopPullGreeting(worker: Worker, client: Client): Promise<void> {
  await client.close();
  await worker.close();
}
```

Example: [examples/typescript/src/production/pull-workers.ts](https://github.com/superdurable/dex/blob/main/examples/typescript/src/production/pull-workers.ts)

## Readiness

TypeScript exposes **waitPullRegistered**, **pullRegistrationState**, and
**stopOnPermanentStreamRejection** in SDK 1.14.0. TypeScript waits accept an
AbortSignal or timeout in milliseconds. Opt-in fatal rejections are returned by
**run** after draining.

A **PullRegistrationError** reports **STEP_AND_RPC** or **RPC_ONLY** as its slot
kind.

Call the boolean helper from your probe endpoint and return 200 when true or
503 when false.

```typescript
export function isPullGreetingReady(worker: Worker): boolean {
  return worker.pullRegistrationState().isReady;
}
```

Example: [examples/typescript/src/production/pull-workers.ts](https://github.com/superdurable/dex/blob/main/examples/typescript/src/production/pull-workers.ts)

## Capacity and shutdown

| Setting            | TypeScript name        |
| ------------------ | ---------------------- |
| Concurrent tasks   | **maxConcurrentTasks** |
| Reserved RPC slots | **reservedRpcTasks**   |
| Stop drain timeout | **stopDrainTimeoutMs** |
| Shutdown           | **close**              |

The idle stream option, **idleStreamsPerQueue**, is deprecated. It is still accepted and
has no effect.

## Reserved RPC capacity

The reserve-decline counter, **pullReservedRpcDeclines**, is deprecated. It remains for
source compatibility and always reads zero.

This diagnostics helper exposes registration readiness. A full Worker stays ready.

```typescript
export interface PullGreetingDiagnostics {
  readonly isReady: boolean;
}

export function getPullGreetingDiagnostics(worker: Worker): PullGreetingDiagnostics {
  return {
    isReady: worker.pullRegistrationState().isReady,
  };
}
```

Example: [examples/typescript/src/production/pull-workers.ts](https://github.com/superdurable/dex/blob/main/examples/typescript/src/production/pull-workers.ts)