Some files disappear from an APFS snapshot 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: &quot;/Users/user/Library/Application Support/Google/Chrome/Default/Local Storage/leveldb/021794.ldb&quot;
file has vanished: &quot;/Users/user/Library/Application Support/Google/Chrome/Default/Local Storage/leveldb/021795.ldb&quot;
file has vanished: &quot;/Users/user/Library/Application Support/Google/Chrome/Default/Local Storage/leveldb/021796.ldb&quot;
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?
The problem lies in the way tmutil works for snapshots, I've created a different question about it.