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

node/src/node_file.cc

Lines 2934 to 2965 in b17a1fb

	static void UTimes(const FunctionCallbackInfo<Value>& args) {
	Environment* env = Environment::GetCurrent(args);
	const int argc = args.Length();
	CHECK_GE(argc, 3);
	BufferValue path(env->isolate(), args[0]);
	CHECK_NOT_NULL(*path);
	ToNamespacedPath(env, &path);
	THROW_IF_INSUFFICIENT_PERMISSIONS(
	env, permission::PermissionScope::kFileSystemWrite, path.ToStringView());
	CHECK(args[1]->IsNumber());
	const double atime = args[1].As<Number>()->Value();
	CHECK(args[2]->IsNumber());
	const double mtime = args[2].As<Number>()->Value();
	if (argc > 3) { // utimes(path, atime, mtime, req)
	FSReqBase* req_wrap_async = GetReqWrap(args, 3);
	FS_ASYNC_TRACE_BEGIN1(
	UV_FS_UTIME, req_wrap_async, "path", TRACE_STR_COPY(*path))
	AsyncCall(env, req_wrap_async, args, "utime", UTF8, AfterNoArgs,
	uv_fs_utime, *path, atime, mtime);
	} else { // utimes(path, atime, mtime)
	FSReqWrapSync req_wrap_sync("utime", *path);
	FS_SYNC_TRACE_BEGIN(utimes);
	SyncCallAndThrowOnError(
	env, &req_wrap_sync, uv_fs_utime, *path, atime, mtime);
	FS_SYNC_TRACE_END(utimes);
	}
	}

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.