Got 502 from function using SvelteKit form action

Support
,
1

Thanks in advance for your help.

My site is: dewdrops.netlify.app, no custom domain yet.

I’m running Svelte 4.2.

I couldn’t find any answers using the AI

I’m using SvelteKit Form Actions, which are run as Netlify functions under the hood. I was getting a mysterious 502 error. I cannot duplicate it locally using Netlify CLI.

I am on the free tier.

The function logs made me suspect I am hitting a memory limit when I saw messages like:

Duration: 475.46 ms Memory Usage: 100 MB Init Duration: 262.86 ms

100MB seemed like a very specific round number so I suspected a memory limit issue (though sometimes memory usage reaches 135MB).

I determined my form was submitting some unneeded data. When I cut out this unneeded data the error goes away.

Interestingly, when I add garbage hidden input fields to my form using the console in Chrome dev tools I can duplicate the issue. This suggests a data size or memory issue.

I add the fields like this:

const form = document.getElementById('yourform');
for (let i = 0; i < 130; i++) { 
	const el = document.createElement('input'); 
	el.type = 'hidden'; 
	el.value = 'RANDOM-DATA-ABC-' + i; 
	el.name = 'root_key_xxx.__id__.field_key_zzz' + i;
	
	form.appendChild(el);
}

I would like to understand what went wrong to make sure I can avoid this in the future.

I’m confused because:

  • 135MB of memory is well below the 1GB limit for Netlify functions
  • the responses come back in under 600ms, so I am not hitting the 10s time limit
  • the form submission, even with extra data, was only about 15kb. That was excessive but well under the 6MB limit for Netlify functions
2

At the moment, your form (I only tested login), seems to be working fine. How to reproduce the issue?