[pbs-devel] [PATCH v4 proxmox-backup 0/5] handle reader client disconnects

[Fiona Ebner]

Am 08.04.25 um 14:58 schrieb Christian Ebner:
> These patches attempt to improve the server side error handling for
> backukp reader client disconnects.
> 
> During regular operation, the server currently cannot distinguish a
> disconnect because of error from a disconnect because of finished
> operation. This leaves behind a task in failed state, which is
> unexpected and might cause confusion [0].
> 
> To improve error handling, follow the approach taken for the backup
> writer tasks, letting the client signal it has successfully finished
> via an api call and catch the disconnect error for that case.
> 
> The signaling of messages/warnings in case of client side aborts
> triggered by the user as suggested by Fabian has not been
> implemented, as that is currently not transparently handled by the
> client (only handled by BackupReader's Drop impl), therefore seemed
> out of scope for this patch series.
> 
> changes since version 3:
> - rebased onto current master
> 
> Reported in the community forum:
> [0] https://forum.proxmox.com/threads/158306/
> 

While I wasn't able to reproduce the exact issue as reported in the
forum thread I was able to run into a slightly different one by issuing
the following two commands

proxmox-backup-client backup --repository 10.10.100.180:bigone
ex.pxar:example
proxmox-backup-client backup --repository 10.10.100.180:bigone
ex.pxar:example --change-detection-mode metadata

resulting in a backup reader task that had to read no chunks (and that
was the correct timing for me to trigger the race I guess):

> 2025-04-09T14:36:21+02:00: starting new backup reader datastore 'bigone': "/mnt/datastore/bigone"
> 2025-04-09T14:36:21+02:00: protocol upgrade done
> 2025-04-09T14:36:21+02:00: TASK ERROR: connection error: connection reset: connection reset

While testing that the refactor for "proxmox-backup-debug diff" did not
mess anything up I ran into a completely different issue, namely, that
it doesn't work for split archives:

> root at pbs1:~# proxmox-backup-debug diff archive ct/131/2025-02-11T12:40:25Z ct/131/2025-04-09T11:29:09Z root.pxar --repository localhost:bigone
> Error: Unable to open dynamic index "/mnt/datastore/bigone/ct/131/2025-04-09T11:29:09Z/root.pxar.didx" - No such file or directory (os error 2)
> root at pbs1:~# ls /mnt/datastore/bigone/ct/131/2025-04-09T11:29:09Z
> client.log.blob  index.json.blob  pct.conf.blob  root.mpxar.didx  root.ppxar.didx


Another issue I found is that using a patched client but unpatched
server will result in a client error:

> Error: Path '/finish' not found.

and non-zero exit code. Can the client check whether the server supports
the new endpoint and handle this gracefully?