Some files disappear from an APFS snapshot

Question

I'm using rsync on top of a mount_apfs snapshots, to backup a consistent file system view and without having to stop applications during the backup.

While so far, it has been working pretty well, from time to time rsync shows messages like:

mount_apfs: snapshot implicitly mounted readonly
file has vanished: "/Users/user/Library/Application Support/Google/Chrome/Default/Local Storage/leveldb/021794.ldb"
file has vanished: "/Users/user/Library/Application Support/Google/Chrome/Default/Local Storage/leveldb/021795.ldb"
file has vanished: "/Users/user/Library/Application Support/Google/Chrome/Default/Local Storage/leveldb/021796.ldb"
rsync warning: some files vanished before they could be transferred (code 24) at main.c(1209) [sender=3.1.3]

Which usually happens when an application interferes with rsync by deleting files in the middle of a backup.

To me, a snapshot is supposed to offer a frozen view of the file system at some point, but maybe it's not exactly like that for an Apple snapshot?

Answer 1

The problem lies in the way tmutil works for snapshots, I've created a different question about it.