Feature Request: Pre-Download completion check

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Geolas
Posts: 12
Joined: 06 May 2013, 19:04

Feature Request: Pre-Download completion check

Post by Geolas » 13 May 2013, 08:54

I've started to use NZBGet on my Raspberry Pi over SABnzbd because of it's faster C code over SABnzbd's python code.

One of the freatures I really miss from SABnzbd though and I think would benefit NZBget would be a pre-download completion check.

Is this possible in NZBGet?

In case it's not clear what I mean here's an explination of how it works in SAB...
Pre-download check (Experimental)

If you are hit by frequent incomplete and non-repairable downloads and worry about wasted time, bandwidth or quota, there's the pre-check.
Before downloading, SABnzbd will check if enough articles are available on the server.
Currently the job will pause when the downloadable parts of the rar and par2 files together are less than 100.2% of the actual rar files.
Below that you will need to decide whether you want to take the risk of downloading something unrepairable.

Note that this an experimental feature, with the following issues:

The pre-download check takes some time, but much less than a (failed) download.
SABnzbd calculates the balance between missing articles and available par2 file. However it's not possible to make a completely accurate prediction, that's why 100.2% of the net payload should be downloadable.
The "payload" above means that the downloadable amount of RAR and PAR2 files should be at least as much as the required amount of RAR files. Anything below 100% is by definition not repairable.
Unfortunately due to weak design of the NZB format and the fact that Usenet articles and par2 repair blocks do not match, SABnzbd cannot make accurate predictions. That's why pre-check requires at least 100.2%1. Note that the average post has 110% data.

If you turn on this feature (Config->Switches), it will be used for all new jobs that enter the queue. When something in the queue is being pre-checked, the mouse-over will show "Status: Checking". Note that during this phase, the download speed shown by SABnzbd will be low (for example "7 kB/s"), and thus the ETA will be very high. You should ignore the high ETA.
When a pre-download check fails, the job will go to History with a message like "Download would not be successful, only 99.5% available "in red. You can click Retry if you want to download anyway.

http://wiki.sabnzbd.org/introducing-0-7-0

hugbug
Developer & Admin
Posts: 7514
Joined: 09 Sep 2008, 11:58
Location: Germany

Re: Feature Request: Pre-Download completion check

Post by hugbug » 13 May 2013, 09:18

Geolas wrote:One of the freatures I really miss
If your concern is about DMCA then there are little reasons to miss the feature:
  • It's not accurate because it doesn't take the damages across par-blocks into account;
  • It's not useful for DMCA posts, it is even not recommended by SAB devs anymore (in favor of new feature "automatic abort");
  • For DMCA posts it's safer to let the program fail with a download instead of doing a precheck. The actual "download" of a missing post is as fast as a precheck because nothing is downloaded (server always returns "article not found error");
  • If you often have problems with non-DMCA posts missing too many blocks, then you should switch your news provider.
The precheck-feature will not be implemented in NZBGet.

What could be possibly implemented is an automatic abort if a post looks not health (DMCA). This has however low priority because trying to download the whole post doesn't take much time anyway. The only "problem" I see is that user need to manually delete the directory of the failed job. This can however be solved using a smart pp-script, which would detect a DMCA'ed download and automatically delete the directory (hint: the script should check if all (or most of) rar-files have zero size).

Edit: "automatic about" -> "automatic abort".

Geolas
Posts: 12
Joined: 06 May 2013, 19:04

Re: Feature Request: Pre-Download completion check

Post by Geolas » 18 May 2013, 13:26

Thanks for your very clear and detailed explanation of why this feature isn't going to implemented hugbug. I guess the one instance (though not really a concern of mine currently) is for anyone who's on a service that cap the bandwidth usage over a month. Can be annoying to download say 5GB of data to find out you're missing an extra 200mb or a similar scenario.
hugbug wrote:What could be possibly implemented is an automatic about if a post looks not health (DMCA). This has however low priority because trying to download the whole post doesn't take much time anyway. The only "problem" I see is that user need to manually delete the directory of the failed job. This can however be solved using a smart pp-script, which would detect a DMCA'ed download and automatically delete the directory (hint: the script should check if all (or most of) rar-files have zero size).
Do you know of any script that does this currently?

hugbug
Developer & Admin
Posts: 7514
Joined: 09 Sep 2008, 11:58
Location: Germany

Re: Feature Request: Pre-Download completion check

Post by hugbug » 18 May 2013, 13:29

Geolas wrote:Do you know of any script that does this currently?
No, this was an idea for a new script. It's not hard to write such a script. If you write or find one - please share.

hugbug
Developer & Admin
Posts: 7514
Joined: 09 Sep 2008, 11:58
Location: Germany

Re: Feature Request: Pre-Download completion check

Post by hugbug » 18 May 2013, 13:34

I've just noticed a misspelling error in my first post:
What could be possibly implemented is an automatic about (automatic ABORT) if a post looks not health (DMCA).

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