WebUI throws "qBittorrent client is not reachable" almost constantly

[radumateibirle]

• qBittorrent version and Operating System Ubuntu 18.04.3 LTS (server edition, headless) qBittorrent-nox 4.1.8

• If on linux, libtorrent-rasterbar and Qt version Qt5 5.13 libtorrent-rasterbar 1.1.5

• What is the problem WebUI shows "qBittorrent client is not reachable" every minute or two or when adding a torrent, regardless of how many torrents are loaded or seeding or doing anything for that matter. It is very difficult to add torrents to download if the WebUI keeps disconnecting. I had to add a torrent around 15 times until it worked. As I migrated my torrents from my Windows machine (from utorrent) to qBittorrent running on my server (set do download to the same smb share as utorrent), I had 23 torrents checking. During this time, WebUI showed the same message at least 30 times and while the message is shown the percentage doesn't update. It sometimes throws the same message when opening settings and almost everytime when i click save.

• What is the expected behavior Was expecting it not to crash all the time

• Steps to reproduce Honestly, just install Ubuntu 18.04.3 or Debian 10 and qBittorrent-nox. It has happened to me on every attempt (and trust me, there were at least 5 with each distro)

• Extra info(if any) The OS runs in a VM in ESXI together with PFSense and FreeNAS, on the same virtual switch. Never had any networking issues.

[Kolcha]

looks like you have some performance issues, very likely disk I/O may be bottleneck. I saw very similar behavior when OS where installed on flash drive which was close to die.

Long time ago I also tried to run torrent client on VM hosted on ESXI server and that was bad idea... Disk I/O is terrible... torrent clients intensively perform random disk I/O, but due to a lot of other VMs running on the same host there is a lack of free RAM (which could be used as disk cache to mitigate performance degradation due to disk I/O) so I/O intensive apps suffer from I/O wait. when processes run any system calls to perform I/O they (processes) go to uninterruptible state (and stop responding) until I/O operation completes.

not only download/upload speed suffer from target downloads disk I/O problems, system disk (where qBittorrent data is saved) is important too (such was in my first case). few files must be created or just updated during adding new torrent, due to bad I/O it can take a lot of time, so WebUI may decide that connection was lost. try to use watched folder and upload torrent files to it, this will significantly mitigate the issue.

also this behavior may be observed due to lack of CPU time (i.e. high CPU load, some VM(s) uses a lot of CPU).

[Kolcha]

moreover, as I understood, your download folder is smb share. it is known that network filesystems has pretty bad random I/O, and to mitigate that they cache a lot of data. in particular case, Samba demonstrate better performance when more RAM is accessible on both sides (smb client and smb server), client side maybe more critical. also smb client causes high CPU usage when performing a lot of I/O operations. I suggest to run torrent client on separate machine, and share downloads folder (i.e. run qBittorent on the same machine as Samba server).

[radumateibirle]

I managed to solve this by slightly increasing RAM for the qbittorrent vm from 512 to 1024. I've never seen it exceed 540mb but hey, it solved problem. I know of the smb issues but this is the simplest way to integrate everything for me and i get 50MBps down speed. Next step is to add some more ram as i only have 1gb for qbittorent vm and 5gb for the freenas vm, but ddr3 is still expensive (well, expensive for me :)) ).