Does fs.utimes invoke utime() or utimes()?

[jsumners-nr]

I have a test against fs.utimes that is flaky. The test:

1. creates a temporary file
2. invokes fs.utimes against that file to set specific accessed & modified times
3. checks that the times are expected in the callback invoked by fs.utimes via fs.statSync

This test is flaking out by the accessed time occasionally, being set to an unexpected time (creation time of the temp file?), e.g. 1732540522.827 == 1732539600.

This comment nodejs/node#30212 (comment) is suggesting that, ultimately, the passed in times are being converted to nanosecond precision. But if I look at:

https://github.com/nodejs/node/blob/b17a1fb1cec919c09aa3401c040b79e35c5ed82e/src/node_file.cc#L2934-L2965

it looks like Node.js will be invoking utime() instead of utimes() (at least, I think that static void UTimes function is what underlies fs.utimes). According to https://linux.die.net/man/2/utimes, only utimes() supports nanosecond precision.

Is my finding correct? Or am I missing something?

[juanarbol]

No, is using futimens in Linux

I'll try to build the backtrace for you.

uv_fs_utime calls an INIT(FUTIME);
https://github.com/libuv/libuv/blob/c6d43bea09093545e0f199921b2d33548a2a1f85/src/unix/fs.c#L1931

Which ends on Linux in a futimens
https://github.com/libuv/libuv/blob/c6d43bea09093545e0f199921b2d33548a2a1f85/src/unix/fs.c#L236

and on macOS utimes
https://github.com/libuv/libuv/blob/c6d43bea09093545e0f199921b2d33548a2a1f85/src/unix/fs.c#L1164 Nevermind

[jsumners-nr]

So, regardless of platform, there is room for conversion error. However, the test I was investigating is likely only failing on macOS -- newrelic/node-newrelic#2790

[juanarbol]

macOS uses futimes, each platform seems to have different "storage" precision/resolution. I don't know if we can do anything as every OS seems to behave different.