Non-deterministic order of backup job arguments

[MasinAD]

Hi, while checking my backup emails I noticed that the issued command varies the order of arguments although no changes where done to the backup job:

vzdump 500 --mailnotification always --mailto <e-mail recipient> --mode snapshot --node appserver3 --storage backupserver1 --quiet 1 --compress zstd vzdump 500 --mailnotification always --node appserver3 --compress zstd --quiet 1 --mailto <e-mail recipient> --storage backupserver1 --mode snapshot vzdump 500 --mailnotification always --quiet 1 --storage backupserver1 --node appserver3 --compress zstd --mailto <e-mail recipient> --mode snapshot vzdump 500 --storage backupserver1 --mailto <e-mail recipient> --compress zstd --quiet 1 --mode snapshot --mailnotification always --node appserver3 vzdump 500 --mailto <e-mail recipient> --node appserver3 --storage backupserver1 --mailnotification always --mode snapshot --compress zstd --quiet 1 vzdump 500 --storage backupserver1 --mode snapshot --mailnotification always --quiet 1 --mailto <e-mail recipient> --node appserver3 --compress zstd

How come? I just ask because non-determinism in regard to backups is a little bit worrisome. I can imagine completely comprehensible reasons but it would be nice to get some affirmation. I guess determining arguments to vzdump is somehow parallized and the seemingly random ordering is caused by different execution times of the different threads.

Bests,
Masin

 

[mira]

That's because Perl hashes are randomly sorted since 5.18.0 [0].
I'd assume all options are stored in a hash and iterated over without sorting when building the command.


[0] https://perldoc.perl.org/perl5180delta#Hash-overhaul

 

[MasinAD]

Ah, that's a good explanation. And far simper than mine .

 

[mira]

Yes, as expected the keys are not sorted. It's the sub command_line in /usr/share/perl5/PVE/VZDump/Common.pm.