Memory leak?

[kevinrenskers]

Describe the bug

I am seeing the memory usage of my SvelteKit app, running with the Node adapter, going up and up. I'm not sure how the server's memory usage can keep increasing, all the svelte stores for example are only used in the browser, and other than that the server requests should be stateless, right?

See https://discord.com/channels/457912077277855764/1081891569390583898 for a discussion about this.

Reproduction

As far as I know, any project will show this problem.

Create a new skeleton project. No need to add TypeScript, Prettier, ESLint or anything else.

npm create svelte@latest repro
cd repro
npm i
npm run build
npm run preview

Open http://127.0.0.1:4173/, open the activity monitor (on macOS) or top or whatever else to see memory usage of the Node process, and refresh the webpage a whole bunch of times. You'll see the memory go up. It's slow to increase with such a simple skeleton project so you might need to refresh a whole bunch of times, but it does go up.

In my moderately popular website it goes up by about 300 MB per day.

Logs

No response

System Info

System:
    OS: macOS 13.2.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 274.47 MB / 32.00 GB
    Shell: 3.6.0 - /opt/homebrew/bin/fish
  Binaries:
    Node: 16.17.0 - ~/Library/pnpm/node
    Yarn: 1.22.19 - /opt/homebrew/bin/yarn
    npm: 8.15.0 - ~/Library/pnpm/npm
  Browsers:
    Chrome: 111.0.5563.64
    Edge: 110.0.1587.69
    Firefox: 110.0.1
    Safari: 16.3
  npmPackages:
    @sveltejs/adapter-auto: ^2.0.0 => 2.0.0
    @sveltejs/kit: ^1.5.0 => 1.11.0
    svelte: ^3.54.0 => 3.56.0
    vite: ^4.0.0 => 4.1.4

Severity

serious, but I can work around it

Additional Information

I have to restart my Node server once in a while or the server just runs out of memory.

[vhscom]

@kevinrenskers this issue appears to be related to Undici, which is used under the hood for the fetch implementation in Node. As a workaround, you may be able to swap out SvelteKit fetch with Axios until this bug is resolved.

[kevinrenskers]

Is that being tracked in their repo somewhere?

Switching to Axios is not really an option, I don't have time to go through the entire app to make such a refactor.

[eltigerchino]

This should be closed by #9591 where we pin undici's version.
@kevinrenskers can you confirm if this issue is still present for you after upgrading to @sveltejs/kit@1.15.1 ?

[kevinrenskers]

I've deployed a new version, will keep an eye on the memory usage and report back.

This was the last 30 days, for reference:

[kevinrenskers]

I don't think that helped, it keeps increasing in basically the same speed as before; 30 MB in 2 hours. Which doesn't sound like a huge amount, but is 360 MB per day.

Update:

It just keeps on rising, no change.

Is nobody else seeing this? Or is nobody else tracking their server stats?

Update 2:

🤷‍♂️

[machycek]

@kevinrenskers we are having the same issue actually

[gtm-nayan]

@kevinrenskers
Was this using the default server that's provided by the adapter or using just the handler in a custom server?

[kevinrenskers]

The default server, using adapter-node.

[gtm-nayan]

And this also happens with npm run preview?

[kevinrenskers]

I don't know, I don't want to run my production website that way to find out 😅 I'll try it locally, see what happens.

[dominikg]

can you please confirm the exact versions of operating system, node, @sveltejs/kit, @sveltejs/adapter-node and undici where you are observing this behavior?

[kevinrenskers]

can you please confirm the exact versions of operating system, node, @sveltejs/kit, @sveltejs/adapter-node and undici where you are observing this behavior?

  System:
    OS: Linux 5.10 Debian GNU/Linux 11 (bullseye) 11 (bullseye)
    CPU: (4) x64 AMD EPYC Processor
    Memory: 4.68 GB / 7.58 GB
    Container: Yes
    Shell: 5.1.4 - /bin/bash
  Binaries:
    Node: 16.19.1 - /usr/bin/node
    npm: 8.19.3 - /usr/bin/npm
  npmPackages:
    @sveltejs/adapter-node: ^1.0.0 => 1.2.3
    @sveltejs/kit: ^1.0.0 => 1.15.4
    svelte: ^3.54.0 => 3.58.0

undici: 5.20.0

[kevinrenskers]

And this also happens with npm run preview?

Yes

[stalkerg]

Can you try "@sveltejs/adapter-node": "1.2.2", and "undici": "5.20.0" and also do this:

"overrides": {
		"@sveltejs/kit": {
			"undici": "$undici"
		},
		"@sveltejs/adapter-node": {
			"undici": "$undici"
		}
	}

I have no issue now. Also, undici devs fixed such a memory leak (very tricky way actually!).

[kevinrenskers]

I'm already using undici 5.20.0 though, but sure I'll try. Where do I put these overrides?

[stalkerg]

on the same level as "devDependencies": { also, very important to downgrade adapter-node as well (undici bundling by bable)

[kevinrenskers]

So far it seems improved, but I'll know for sure in a day or so. I'll report back.

Update: after 4 hours memory usage has increased by about 15 MB. Let's see what's it like in 24 hours.

[kevinrenskers]

I think the leak is indeed solved 🎉
At first the memory increased by about 15 MB, but it's been stable at ~60 MB for about 12 hours now. Huge difference.

[dummdidumm]

@stalkerg am I seing this correctly that undici has released the fix for the memory leak in https://github.com/nodejs/undici/releases/tag/v5.21.1 so we can bump to latest undici again?

[stalkerg]

@dummdidumm yes! Now it's fixed without a timeout breakage. My small local tests are working well.

[kevinrenskers]

This fix isn't released yet, right? Because I updated all my dependencies, removed the overrides, and the problem is back in full force.

You can clearly see when I deployed the changes 😅

[eltigerchino]

This fix isn't released yet, right? Because I updated all my dependencies, removed the overrides, and the problem is back in full force.

No, it has not released yet.

[kevinrenskers]

Is there an ETA on a release? So I can decide if I should revert my change or just wait a bit.

[eltigerchino]

Is there an ETA on a release? So I can decide if I should revert my change or just wait a bit.

It's out now! :) https://github.com/sveltejs/kit/releases/tag/%40sveltejs%2Fkit%401.15.8

[stalkerg]

@s3812497 it's not enough; we also must update the node adapter because of bundling (this issue is not in direct dependencies)

[eltigerchino]

@s3812497 it's not enough; we also must update the node adapter because of bundling (this issue is not in direct dependencies)

Ah, sorry about that. I didn't know.

[stalkerg]

@s3812497 @sveltejs/adapter-node/files/shims.js still includes old undici and the node adapter will use it.

[stalkerg]

@dummdidumm we must update adapter-node as well, just sveltekit is not enough.

[itssumitrai]

Can we fix this asap ? Our production server capacity is lost by more than 100%. Basically we need to have more than twice the servers and the perf has become really bad as well. We have no choice other than to pin down adapter node. Can this issue get more traction ?