Next 9.5.1 out of memory after some hot reloads

Bug report

Describe the bug

Since updating to 9.5.x (from 9.4.x), i get an out of memory error after 10 something hot reloads:

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory

it did rarely happen in 9.4.1, but it happens very consistantly in 9.5.x

To Reproduce

thats probably tricky. it happens on big projects and might be related to some bug in the hot reload / rebuild. Maybe it happens when there are some import circles?

Expected behavior

nextjs should not go out-of-memory

System information

• OS:macOS
• Browser: chrome
• Version of Next.js: 9.5.1
• Version of Node.js: 12.13.1

Additional information

we are using a custom server with typescript

[macrozone]

Please provide a reproduction so that we can investigate

this is extremly hard to do, but i am 100% sure others have the same issue. Do you hav any idea how this could happen? Its a new problem and happens very consistantly.

maybe circular dependencies? I investigate now in that

[sbinlondon]

Just a small update:

Used node-oom-heapdump to grab a heap snapshot of our app when it crashed.

It seems to call out one of Webpack’s dependencies, watchpack (and its DirectoryWatcher.js), which makes sense to me because my crashes happen the most when I’m in dev mode, switching between branches that have a large number of changed files between them.

I have sent the heap snapshot to the Next.js team so hopefully it will help them look into this. I think I’m potentially going to open an issue on the Watchpack repo as well.