Express and Fastify

Inngest invokes a function by calling your application over HTTP, so the strategy does not open a port: it mounts Inngest's own serve handler on the application's HTTP server. Both of Nest's official adapters are supported, and which one is in use is read from the adapter.

adapter	mounted with	as
ExpressAdapter (Nest's default)	inngest/express	app.use(servePath, handler)
FastifyAdapter	inngest/fastify	fastify.register(plugin, { servePath })

The serve path answers GET (introspection), PUT (registration) and POST (invocation).

Start the microservice before listening

const app = await NestFactory.create(AppModule);
app.connectMicroservice({ strategy: new InngestStrategy({ inngest, httpAdapter: app.getHttpAdapter() }) });
await app.startAllMicroservices(); // 1. mounts /api/inngest
await app.listen(3000);            // 2. initializes and listens

The strategy mounts a route, and a route has to exist before the server starts answering:

• on Express, a route added after app.init() lands behind Nest's not-found handler, and every call to it answers 404;
• on Fastify, a plugin cannot be registered once the instance has booted, which Nest does in listen().

Starting the microservices first is right on both. When the server is already listening, the strategy refuses to start, with a message saying what to do, instead of serving nothing.

Express and the request body

Nest registers its JSON body parser when the application initializes — after the strategy has mounted. On Express, the strategy therefore reads the JSON body itself when nothing has read it yet, and leaves alone a body some parser already read. Nothing needs configuring, and it works with bodyParser: false too.

A global prefix

app.setGlobalPrefix('api') applies to Nest's own routes, not to this one: the functions are served at servePath exactly. Set servePath to whatever URL Inngest should call.

Testing with Fastify

When a test calls app.init() and drives the server with supertest instead of listening, Fastify has to be told it is ready, as for any Fastify route in Nest:

await app.startAllMicroservices();
await app.init();
await app.getHttpAdapter().getInstance().ready();