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Next Dev Overrides Container-Aware V8 Heap Limit Using Host Memory

Next.js dev server calculates the V8 max-old-space-size based on host total memory (os.totalmem()), ignoring container memory constraints. In a Docker container with a memory limit, this sets an excessively high heap limit, potentially leading to out-of-memory (OOM) kills or performance degradation. Node.js already provides process.constrainedMemory() which respects cgroup limits; Next.js should use it when available.

highConfidence 95%Next.js Affected V14.0.0 Affected V15.0.0 Affected V16.0.0 Affected V16.3.4 Affected V16.4.0-Canary.21

Origin Analysis

The heuristic in next-dev.ts (introduced in PR #57163) uses os.totalmem() * 0.5 to set --max-old-space-size, overriding Node's runtime-aware default. In containerized environments, os.totalmem() returns the host's total memory, not the container's cgroup limit, causing an inflated heap size.

1. Run a Docker container with a memory limit, e.g., docker run --rm -m 2g node:22. 2. Inside the container, create a Next.js app using create-next-app. 3. Start next dev and inspect the NODE_OPTIONS environment variable set by Next.js. 4. Observe that --max-old-space-size is set to approximately half of host memory (e.g., 15890 MB on a 32GB host) instead of a container-appropriate value (around 1048 MB).

Fixing Code Block

0x7F 45 4C 46 02 01 01 000x90 12 AB 04 C1 7E 33 08
0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
0x00 00 00 00 03 00 3E 000x01 00 B7 4D 55 90 0C 61
0x6C 69 62 63 2E 73 6F 2E0x36 00 8E 17 42 AA 05 F3
0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

process.constrainedMemory() may not be available on all Node versions or platforms; the fallback handles that. In some environments (e.g., cgroup v1 with certain configurations), constrainedMemory might return 0 or an inaccurate value, leading to the old behavior. Additionally, users who previously relied on NEXT_DISABLE_MEM_OVERRIDE or manual NODE_OPTIONS should still see those respected, as the fix only changes the default calculation. Rolling back this change would revert to the host-memory heuristic, so no special rollback steps are needed beyond reverting the code.