[pbs-devel] [PATCH proxmox-backup 4/5] backup: use flock on backup group to forbid multiple backups at once

[Stefan Reiter]

On 7/30/20 7:50 AM, Dietmar Maurer wrote:
>> +        // acquire in non-blocking mode, no point in waiting here since other
>> +        // backups could still take a very long time
>> +        tools::lock_file(&mut handle, true, Some(Duration::from_nanos(0)))
>> +            .map_err(|err| {
>> +                match err.downcast_ref::<nix::Error>() {
>> +                    Some(nix::Error::Sys(nix::errno::Errno::EAGAIN)) => {
> 
> Honestly, I would remove this special case with downcast - the default error message is good enough. Isn't it?
> 

The original message ends in "EAGAIN - Try again", which to me sounded 
like inviting the user to just run the command again, instead of telling 
them there's a backup running.

>> +                        return format_err!(
>> +                            "unable to acquire lock on backup group {:?} - another backup is already running",
>> +                            self.group_path(),
>> +                        );
>> +                    },
>> +                    _ => ()
>> +                }
>> +                format_err!(
>> +                    "unable to acquire lock on backup group {:?} - {}",
>> +                    self.group_path(),
>> +                    err,
>> +                )
>> +            })?;
>> +
>> +        Ok(handle)
>> +    }
>> +