Vercel Deployments are erroring only in prod (not in dev, not in preview)

[bent101]

Describe the bug

see this discussion for more info

Reproduction

repro, just a skeleton project with a routes/+page.svelte and a routes/+page.ts loading dummy json
failed vercel deployment

Logs

TypeError: Failed to parse URL from [object Request]
at Object.fetch (node:internal/deps/undici/undici:11576:11)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
at async Object.fetch (file:///var/task/.svelte-kit/output/server/index.js:2372:12)
at async file:///var/task/.svelte-kit/output/server/index.js:740:20
at async file:///var/task/.svelte-kit/output/server/index.js:629:86
at async Promise.all (index 0)
at async unwrap_promises (file:///var/task/.svelte-kit/output/server/index.js:629:9)
at async load_data (file:///var/task/.svelte-kit/output/server/index.js:733:25)
at async file:///var/task/.svelte-kit/output/server/index.js:2106:18 {
[cause]: TypeError [ERR_INVALID_URL]: Invalid URL
at new NodeError (node:internal/errors:405:5)
at new URL (node:internal/url:637:13)
at new Request (node:internal/deps/undici/undici:7132:25)
at fetch2 (node:internal/deps/undici/undici:10715:25)
at Object.fetch (node:internal/deps/undici/undici:11574:18)
at fetch (node:internal/process/pre_execution:242:25)
at n (/var/task/___vc/__launcher/__launcher.js:14:5526)
at fetch (file:///var/task/.svelte-kit/output/server/index.js:2394:18)
at #options.hooks.handleFetch (file:///var/task/.svelte-kit/output/server/index.js:2919:79)
at Object.fetch (file:///var/task/.svelte-kit/output/server/index.js:2372:33) {
input: '[object Request]',
code: 'ERR_INVALID_URL'
}
}

System Info

vercel :D

Severity

blocking all usage of SvelteKit

Additional Information

No response

[lennart-jaervinen]

I have the exact same error since I deployed yesterday (nothing grave did really change within the code and reverting the changes and re-deploying didn't fix the error. I'm also using the adapter-vercel).

Glad I only pushed to staging yesterday, but this blocks all live deployments, which I will need to hold until the issue gets resolved.

[dummdidumm]

It looks like the cause is nodejs/undici#2374 in combination with us always polyfilling undici. I suspect that Vercel bumped the Node 18 version recently, which includes this bug, and therefore all subsequent deployments fail. As a quickfix you can tell Vercel to deploy to Node 16 on the settings main page (scroll down to "Node.js version"), or to deploy to the edge runtime instead (if that's possible for your setup).

[dummdidumm]

So it seems the linked issue was red herring, as it was closed as a duplicate of something else and that issue was fixed and released a few days ago - and I can reproduce this with the latest version of undici. I'm very confused now as to what could cause this.

[benmccann]

Hmm. They edited the issue it was closed in favor of. They were previously saying nodejs/node#50263. Perhaps this is caused by that issue?

[dummdidumm]

Mhm okay. But why is the polyfill failing with a older versions of undici, too, then? It's very strange, and I'm tempted to add something to the polyfill code to check for specific node versions and not apply them there.

[benmccann]

We only need to polyfill < Node 18.11:

kit/packages/kit/src/exports/node/polyfills.js

Line 24 in bfa2b6e

// TODO: remove this once we only support Node 18.11+ (the version multipart/form-data was added)

I'd be fine with removing the polyfill on older Node versions. Though it's unclear to me what Node versions are being affected by this bug and whether that would fix anything.

[dummdidumm]

We can't completely, crypto is still webcrypto in node - but yeah, we could add a check for the node version and avoid it. In my local testing this fixes the issue.

[dummdidumm]

Sveltekit 1.27.1 hopefully fixes this

[echocrow]

Temporarily falling back to node16 on Vercel as suggested in #10918 (comment) circumvented the issue for us.

Just updated SvelteKit to 1.27.1 and reverted to node18; can confirm server-side fetches are working again. ✅

Thanks for the quick hotfix @dummdidumm!

[benmccann]

Thanks for confirming the fix