rembExample app
The best way to start with the Fastify adapter is to take a look at the example application.
Description
Links
-
Fastify server with WebSocket
-
Simple tRPC client in node
How to use tRPC with Fastify
Install dependencies
bash
yarn add @trpc/server fastify zod
⚠️ Fastify version requirement
The tRPC v11 Fastify adapter requires Fastify v5+. Using Fastify v4 may cause requests to return empty responses without errors.
Zod isn't a required dependency, but it's used in the sample router below.
AI Agents
If you use an AI coding agent, install tRPC skills for better code generation:
bash
npx @tanstack/intent@latest install
Create the router
First of all you need a router to handle your queries, mutations and subscriptions.
A sample router is given below, save it in a file named router.ts.
router.ts
If your router file starts getting too big, split your router into several subrouters each implemented in its own file. Then merge them into a single root appRouter.
Create the context
Then you need a context that will be created for each request.
A sample context is given below, save it in a file named context.ts:
context.ts
Create Fastify server
tRPC includes an adapter for Fastify out of the box. This adapter lets you convert your tRPC router into a Fastify plugin. In order to prevent errors during large batch requests, make sure to set the maxParamLength Fastify option to a suitable value, as shown.
tip
Due to limitations in Fastify's plugin system and type inference, there might be some issues getting for example onError typed correctly. You can add a satisfies FastifyTRPCPluginOptions<AppRouter>['trpcOptions'] to help TypeScript out and get the correct types.
server.ts
ts
import {
fastifyTRPCPlugin,
FastifyTRPCPluginOptions,
} from '@trpc/server/adapters/fastify';
import fastify from 'fastify';
import { createContext } from './context';
import { appRouter, type AppRouter } from './router';
const server = fastify({
routerOptions: {
`maxParamLength: 5000,`
},
});
server.register(fastifyTRPCPlugin, {
prefix: '/trpc',
trpcOptions: {
`router: appRouter,`
`createContext,`
`onError({ path, error }) {`
`// report to error monitoring`
``console.error(`Error in tRPC handler on path '${path}':`, error);``
`},`
} satisfies FastifyTRPCPluginOptions<AppRouter>['trpcOptions'],
});
(async () => {
try {
`await server.listen({ port: 3000 });`
} catch (err) {
`server.log.error(err);`
`process.exit(1);`
}
})();
Your endpoints are now available via HTTP!
Endpoint
HTTP URI
getUserById
GET http://localhost:3000/trpc/getUserById?input=INPUT
where INPUT is a URI-encoded JSON string.
createUser
POST http://localhost:3000/trpc/createUser
with req.body of type User
Enable WebSockets
The Fastify adapter supports WebSockets via the @fastify/websocket plugin. All you have to do in addition to the above steps is install the dependency, add some subscriptions to your router, and activate the useWSS option in the plugin. The minimum @fastify/websocket version required is 3.11.0.
Install dependencies
bash
yarn add @fastify/websocket
Import and register @fastify/websocket
ts
import ws from '@fastify/websocket';
server.register(ws);
Add some subscriptions
Edit the router.ts file created in the previous steps and add the following code:
router.ts
ts
import { initTRPC } from '@trpc/server';
const t = initTRPC.create();
export const appRouter = t.router({
randomNumber: t.procedure.subscription(async function* () {
`while (true) {`
`yield { randomNumber: Math.random() };`
`await new Promise((resolve) => setTimeout(resolve, 1000));`
`}`
}),
});
Activate the useWSS option
server.ts
ts
import {
fastifyTRPCPlugin,
FastifyTRPCPluginOptions,
} from '@trpc/server/adapters/fastify';
import fastify from 'fastify';
import { createContext } from './context';
import { appRouter, type AppRouter } from './router';
const server = fastify();
server.register(fastifyTRPCPlugin, {
useWSS: true,
trpcOptions: {
`router: appRouter,`
`createContext,`
`// Enable heartbeat messages to keep connection open (disabled by default)`
`keepAlive: {`
`enabled: true,`
`// server ping message interval in milliseconds`
`pingMs: 30000,`
`// connection is terminated if pong message is not received in this many milliseconds`
`pongWaitMs: 5000,`
`},`
},
});
You can now subscribe to the randomNumber topic and should receive a random number every second 🚀.
Fastify plugin options
name
type
optional
default
description
prefix
string
true
"/trpc"
URL prefix for tRPC routes
useWSS
boolean
true
false
Enable WebSocket support via @fastify/websocket
trpcOptions
FastifyHandlerOptions<AppRouter, Request, Reply>
false
n/a
tRPC handler options including router, createContext, etc.