Similar to urql's exchanges or Apollo's links. Links enables you to customize the flow of data between tRPC Client and the tRPC-server.

Request Batching​

Request batching is automatically enabled which batches your requests to the server, this can make the below code produce exactly one HTTP request and on the server exactly one database query:

ts

// below will be done in the same request when batching is enabled

const somePosts = await Promise.all([

client.query('post.byId', 1),

client.query('post.byId', 2),

client.query('post.byId', 3),

]);

Customizing data flow​

The below examples assuming you use Next.js, but the same as below can be added if you use the vanilla tRPC client

Setting a maximum batch size​

This limits the number of requests that can be sent together in batch ( useful to prevent the url from getting too large and run into HTTP error 413 ).

server.ts

ts

// 👇 import the httpBatchLink

import { httpBatchLink } from '@trpc/client/links/httpBatchLink';

import { withTRPC } from '@trpc/next';

import { AppType } from 'next/dist/shared/lib/utils';

import type { AppRouter } from 'pages/api/trpc/[trpc]';

const MyApp: AppType = ({ Component, pageProps }) => {

return <Component {...pageProps} />;

};

export default withTRPC<AppRouter>({

config() {

`return {`

  `links: [`

    `httpBatchLink({`

      `url: '/api/trpc',`

      `maxBatchSize: 10, // a reasonable size`

    `}),`

  `],`

`};`

},

})(MyApp);

Disabling request batching​

1. Disable batching on your server:​

In your [trpc].ts:

pages/api/trpc/[trpc].ts

ts

export default trpcNext.createNextApiHandler({

// [...]

// 👇 disable batching

batching: {

`enabled: false,`

},

});

2. Use batch-free link in your tRPC Client​

pages/_app.tsx

tsx

// 👇 import the httpLink

import { httpLink } from '@trpc/client/links/httpLink';

import { withTRPC } from '@trpc/next';

import { AppType } from 'next/dist/shared/lib/utils';

import type { AppRouter } from 'pages/api/trpc/[trpc]';

const MyApp: AppType = ({ Component, pageProps }) => {

return <Component {...pageProps} />;

};

export default withTRPC<AppRouter>({

config() {

`return {`

  `links: [`

    `httpLink({`

      `url: '/api/trpc',`

    `}),`

  `],`

`};`

},

// ssr: false,

})(MyApp);

Using a splitLink to control request flow​

Disable batching for certain requests​

1. Configure client / _app.tsx​

pages/_app.tsx

tsx

import { httpBatchLink } from '@trpc/client/links/httpBatchLink';

import { httpLink } from '@trpc/client/links/httpLink';

import { splitLink } from '@trpc/client/links/splitLink';

import { withTRPC } from '@trpc/next';

// [..]

export default withTRPC<AppRouter>({

config() {

``const url = `http://localhost:3000`;``

`return {`

  `links: [`

    `splitLink({`

      `condition(op) {`

        `` // check for context property `skipBatch` ``

        `return op.context.skipBatch === true;`

      `},`

      `// when condition is true, use normal request`

      `true: httpLink({`

        `url,`

      `}),`

      `// when condition is false, use batching`

      `false: httpBatchLink({`

        `url,`

      `}),`

    `}),`

  `],`

`};`

},

})(MyApp);

2. Perform request without batching​

MyComponent.tsx

tsx

export function MyComponent() {

const postsQuery = trpc.useQuery(['posts'], {

`context: {`

  `skipBatch: true,`

`},`

});

return (

`<pre>{JSON.stringify(postsQuery.data ?? null, null, 4)}</pre>`

)

})

or:

client.ts

ts

const postResult = client.query('posts', null, {

context: {

`skipBatch: true,`

},

});

Creating a custom link​

pages/_app.tsx

tsx

import { TRPCLink } from '@trpc/client';

import type { AppRouter } from 'pages/api/trpc/[trpc]';

const customLink: TRPCLink<AppRouter> = (runtime) => {

// here we just got initialized in the app - this happens once per app

// useful for storing cache for instance

return ({ prev, next, op }) => {

`// this is when passing the result to the next link`

`next(op, (result) => {`

  `// this is when we've gotten result from the server`

  `if (result instanceof Error) {`

    `// maybe send to bugsnag?`

  `}`

  `prev(result);`

`});`

};

};

export default withTRPC<AppRouter>({

config() {

`return {`

  `links: [`

    `customLink,`

    `// [..]`

    `` // ❗ Make sure to end with a `httpBatchLink` or `httpLink` ``

  `],`

`};`

},

// ssr: false

})(MyApp);