Batching - safeguard for max url length

👋 Do you want to pick this up? See https://github.com/trpc/trpc/issues/506#issuecomment-1016626260

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Challenge described:

• Max characters for a url is ~2k characters (I think)
• Currently the batching lumps everything in a request as /api/trpc/posts.byId,posts.byId.query,posts.byId?batch=1&input=${encodeURIComponent(JSON.stringify(input))}

This could potentially lead to situations where the client constructs a url that is too long.

A few things we could do to prevent this

• Change the way we build the query
  • Given query, this could be built like like /api/trpc/3*posts.byId?batch=x
• Make sure the data loader splits up the queries into separate requests when exceeding limit of x
• What I don’t want to do is to use anything but GET for queries

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Refs in the code

• https://github.com/trpc/trpc/blob/main/packages/client/src/internals/dataLoader.ts
• https://github.com/trpc/trpc/blob/main/packages/client/src/internals/httpRequest.ts

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I think the best interface way of handling this is to allow doing httpBatchLink({ maxURILength: 2048 }).

[KATT]

https://github.com/trpc/trpc/releases/tag/v9.18.0

[KATT]

Yes! Here’s some rough steps:

• Add maxBatchSize?: number to httpBatchLink
  • Note: create new interface HTTPBatchLinkOptions extends HTTPLinkOptions { maxBatchSize?: number }
• Add new opts?: { maxBatchSize?: number } to https://github.com/trpc/trpc/blob/main/packages/client/src/internals/dataLoader.ts#L23
• Forward the options from httpBatchLink to dataLoader (https://github.com/trpc/trpc/blob/71568822249cfd9178b2ca63d5dbb376e8bbf1de/packages/client/src/links/httpBatchLink.ts#L40-L42)
• Add circuit-breaker to call dispatch() if length exceeds maxBatchSize here: https://github.com/trpc/trpc/blob/main/packages/client/src/internals/dataLoader.ts#L71
• Add a test similar to https://github.com/trpc/trpc/blob/main/packages/server/test/index.test.tsx#L543
• Add to docs in https://github.com/trpc/trpc/blob/main/www/docs/client/links.md or break the batching docs out to it’s own page