Creating a Vercel CRON job

[zkSoju]

I'm currently trying to create a vercel CRON job that executes a transaction every 7 days, but viem relies on the NodeJs crypto, which gives me this error. I initially built the script without React in mind so I didn't use wagmi.

Failed to compile.

node:crypto
Module build failed: UnhandledSchemeError: Reading from "node:crypto" is not handled by plugins (Unhandled scheme)

Any ideas how to fix?

[fubhy]

Hi. Viem does not rely on node:crypto. I just tried deploying a basic serverless function to vercel and that worked. Do you have a minimal repro that you can share?

[zkSoju]

Solved it!

Looks like it was an issue caused by running it on the Edge, which I just copied.

export const config = {
  runtime: "edge",
};

[fubhy]

Ok, I can confirm that it doesn't work on the edge runtime. But that's not because of node:crypto (viem doesn't use that), but because of stream, fs and url leaking into the viem from downstream deps it seems. I haven't investigated further yet but that's the error I'm seeing. Not sure if we should strive to be edge deployable @jxom @tmm?

[fubhy]

If we want that, then we'd likely have to exclude the websocket transport from the default export.

[fubhy]

Same with a hypothetical future ipc transport that'd likely leverage fs

[fubhy]

Ok, I can confirm that this is possible by just removing the websocket transport from the entrypoint. I think it's worth doing (./cc @jxom @tmm). The coldstart time benefits of edge function vs. serverless function are worth it imho. Would likely also mean that this then works on cloudflare edge & aws lambda without extra work.

[fubhy]

This works:

https://viem-edge-fubhy.vercel.app/api/block?block=17043877
https://github.com/fubhy/viem-edge-example

Cold start times are significantly faster than with a serverless function.

[jxom]

Interesting! We use isomorphic-ws to figure out which websocket impl to use. Can we modify it to throw on serverless?

[fubhy]

The problem appears to be that vercel's build doesn't like the existence of the import in the bundle at all. So even if we make that conditional I don't think that'd solve it. I'll continue to experiment though. Worst case, we'd simply have to provide a dedicated viem/websocket export and include everything related to isomorphic-ws in there (and only there).

[jxom]

Makes sense. If a conditional dynamic import might not work, an entrypoint might be the way to go.

[fubhy]

@jxom Scratch that, we can indeed use a dynamic import. I had simply missed one. So, we can now claim that viem also works on edge runtimes! I'll put up the PR shortly.

[fubhy]

This works now with both edge & serverless:

https://viem-edge-fubhy.vercel.app/api/edge?block=17043877
https://viem-edge-fubhy.vercel.app/api/serverless?block=17043877

https://github.com/fubhy/viem-edge-example

The PR is super simple: #375

[fubhy]

Also possibly related PR: vercel/next.js#45149

[zkSoju]

The problem you last posted seems to be a next.js / webpack issue, not a vercel edge function issue: vercel/next.js#28774

There's also a workaround in that issue.

I believe you're right, I'm seeing this issue when upgrading to any Next version after 13.1.6.

[zkSoju]

vercel/next.js#47314 (comment)

I'm not sure if this is related, since it seems to have worked on that version of Next but not newer ones

[zkSoju]

mattddean/t3-app-router-edge-drizzle#4

I think this might be the solution for the problem.

[fubhy]

Yeah we did that here too: https://github.com/jxom/viem-nextjs-edge

Sorry, should've reported back here ;-)