[pbs-devel] [PATCH proxmox 1/2] rest-server: handle failure in worker task setup correctly

[Thomas Lamprecht]

Am 29.11.24 um 14:13 schrieb Fabian Grünbichler:
> if setting up a new worker fails after it has been inserted into the
> WORKER_TASK_LIST, we need to clean it up instead of bubbling up the error right
> away, else we "leak" the worker task and it never finishes..
> 
> Signed-off-by: Fabian Grünbichler <f.gruenbichler at proxmox.com>
> ---
> we probably want to optimize update_active_workers as well to reduce the lock
> contention there that triggers this issue in the first place..
> 
>  proxmox-rest-server/src/worker_task.rs | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/proxmox-rest-server/src/worker_task.rs b/proxmox-rest-server/src/worker_task.rs
> index 6e76c2ca..3ca93965 100644
> --- a/proxmox-rest-server/src/worker_task.rs
> +++ b/proxmox-rest-server/src/worker_task.rs
> @@ -923,7 +923,12 @@ impl WorkerTask {
>              set_worker_count(hash.len());
>          }
>  
> -        setup.update_active_workers(Some(&upid))?;
> +        let res = setup.update_active_workers(Some(&upid));
> +        if res.is_err() {
> +            // needed to undo the insertion into WORKER_TASK_LIST above
> +            worker.log_result(&res);
> +            res?
> +        }

Seems OK from a quick look, need a bit more time for a proper review.

What the quick look can give though is style nits, i.e. IMO a bit unidiomatic for our
code.

Would prefer one of:

Combined return path through matching

match setup.update_active_workers(Some(&upid)) {
   Err(err) => {
        // needed to undo the insertion into the active WORKER_TASK_LIST above
        worker.log_result(&res);
        Err(err)
   }
   Ok(_) => Ok((worker, logger))
}

or similar than yours but avoid the outer variable:

if let Err(err) = setup.update_active_workers(Some(&upid)) {
    // needed to undo the insertion into the active WORKER_TASK_LIST above
    worker.log_result(&res);
    return Err(err);
}

IMO both fit slightly (!) better for how errors are commonly dealt with in rust and
are thus a bit easier to understand correctly on reading.

>  
>          Ok((worker, logger))
>      }