Express

This guide adds Nelkap to an Express 5 app. By the end, your app will run a workflow that creates a new user’s profile, waits a day, and sends them a welcome email, and you’ll follow each step in your project. You need a Nelkap project with its endpoint, an API key, and its secret. If you don’t have them yet, follow the first three steps of the quickstart.

Install the SDK

npm install @nelkap/sdk

pnpm add @nelkap/sdk

yarn add @nelkap/sdk

Add your keys

Set your project’s API key and secret as environment variables wherever your app runs:

.env

NELKAP_API_KEY=your-api-key
NELKAP_SECRET=your-project-secret

The SDK reads both values from process.env. Node.js doesn’t load .env on its own: start your app with node --env-file=.env, or set the variables in your host’s settings. The API key lets your app start runs and save steps. The secret lets your app check that each call really comes from Nelkap.

Create your client and your first workflow

Create src/nelkap.ts:

src/nelkap.ts

import { Nelkap } from '@nelkap/sdk';

import { createProfile, sendWelcomeEmail } from './activities';

export const nelkap = new Nelkap();

export async function onboardUser(userId: string) {
  await nelkap.step.run('profile', () => createProfile(userId));

  await nelkap.step.sleep('1 day');

  await nelkap.step.run('welcome', () => sendWelcomeEmail(userId));
}

nelkap.registerWorkflows([{ name: 'onboardUser', handler: onboardUser }]);

onboardUser is your workflow: an async function that takes the run’s payload, here a user ID.
Each step.run saves what its function returns. When the run picks up after the sleep, the profile step gives back its saved result instead of creating the profile again.
step.sleep pauses the run for a day. Nothing runs in your app during that day.
registerWorkflows tells Nelkap which workflows your app runs, as soon as the file is loaded.

Replace createProfile and sendWelcomeEmail with your own functions.

Add the route Nelkap calls

nelkap.handle takes a standard web Request, while Express gives you its own request object. The route below builds a standard Request from it, passes it to handle, and sends back the answer:

src/index.ts

import express from 'express';
import { Readable } from 'node:stream';

import { nelkap } from './nelkap';

const app = express();

app.post('/api/nelkap', async (req, res) => {
  const request = new Request(new URL(req.originalUrl, `${req.protocol}://${req.get('host')}`), {
    method: 'POST',
    headers: { authorization: req.get('authorization') ?? '' },
    body: Readable.toWeb(req) as ReadableStream,
    duplex: 'half',
  });

  const response = await nelkap.handle(request);

  res.status(response.status).json(await response.json());
});

app.use(express.json());

app.listen(3000);

The request’s body streams straight into handle, so a run with many saved steps isn’t held back by a body size limit.
Add this route before app.use(express.json()). Otherwise Express reads the body first, and handle gets an empty one.
handle checks the secret, answers Nelkap at once, and runs the workflow in the background. Your server keeps running after the answer, so the run goes on until it completes or pauses.

If your app checks sign-in on every route, leave /api/nelkap out: handle checks Nelkap’s secret instead.

Deploy and set your endpoint

Deploy your app, so Nelkap can reach the route over the internet. Then edit your project and set its endpoint to the route’s URL, like https://your-app.com/api/nelkap.

Start a run

Start the workflow from any route of your app. Here, a sign-up route starts it once the user is created:

src/index.ts

import express from 'express';
import { Readable } from 'node:stream';

import { nelkap, onboardUser } from './nelkap';
import { createUser } from './users';

const app = express();

app.post('/api/nelkap', async (req, res) => {
  const request = new Request(new URL(req.originalUrl, `${req.protocol}://${req.get('host')}`), {
    method: 'POST',
    headers: { authorization: req.get('authorization') ?? '' },
    body: Readable.toWeb(req) as ReadableStream,
    duplex: 'half',
  });

  const response = await nelkap.handle(request);

  res.status(response.status).json(await response.json());
});

app.use(express.json());

app.post('/sign-up', async (req, res) => {
  const user = await createUser(req.body);

  await nelkap.run(onboardUser, user.id);

  res.json({ userId: user.id });
});

app.listen(3000);

run returns as soon as Nelkap has the run, so the sign-up doesn’t wait for the workflow. Its second argument, user.id, is the run’s payload: Nelkap passes it to onboardUser.

Follow your run

Open your project’s runs. The new run shows the profile step with what it returned, then sleeps. A day later, Nelkap calls your route again, the welcome email goes out, and the run completes.

Get started

Concepts

Frameworks

Triggers

Write workflows

Deploy

Monitor

Manage

Help