TypeScript Workers

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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 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 for startup details.

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

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.

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

Example: 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.

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