Abnormal delays in download

[Maxim Dounin]

Hello!

On Mon, Aug 02, 2021 at 02:46:03PM +0200, Pierre Couderc wrote:

> On 8/2/21 1:19 AM, Maxim Dounin wrote:
> > Hello!
> >
> > On Sun, Aug 01, 2021 at 10:38:48PM +0200, Pierre Couderc wrote:
> >
> >> On 8/1/21 3:32 AM, Maxim Dounin wrote:
> >>> Hello!
> >>>
> >>> On Fri, Jul 30, 2021 at 10:40:00AM +0200, Pierre Couderc wrote:
> >>>
> >>>> I am trying to download a 12M pdf file and it takes more than 4 minutes
> >>>> with http nginx while it takes a few seconds with scp.
> >>>>
> >>>> I have asked detailed log here https://paste.debian.net/1206029/
> >>>>
> >>>> I see timeouts but I am not able to interpret them correctly.
> >>>>
> >>>> nginx is in lxd container in a nearly not used  server (htop load
> >>>> average 0.08 ...).
> >>>>
> >>>> I use nearly defaut debian configuration of nginx.
> >>> The logs provided suggest that the client is limiting download
> >>> rather than nginx.  Further, the client seems to do at least 17
> >>> various range requests to the file which is being downloaded, thus
> >>> downloading many more than the file itself, but this is probably
> >>> not the issue.  Rather, the issue seems that the client does not
> >>> proceed with the file download while doing these requests.
> >>>
> >>> Try disabling Firefox PDF Viewer to see if it helps (Preferences
> >>> -> General -> Applications -> Portable Document Format (PDF), set
> >>> to "Save File", see [1]).  Alternatively, try using curl (or wget,
> >>> or fetch, or whatever you prefer) to download the file instead of
> >>> trying to view it in the browser.
> >>>
> >>> [1] https://support.mozilla.org/en-US/kb/view-pdf-files-firefox-or-choose-another-viewer#w_disable-the-built-in-pdf-viewer-and-use-another-viewer
> >>>
> >> Thank you very much, I had not the idea it could be a client such as
> >> firefox, which I suppose bulletproof...
> >>
> >> So I followed your idea and tried with wget : about  2 minutes 40s..
> >>
> >> This is too much long too as with scp (in wifi at 2meters from the
> >> server) it is only 3 seconds... ;)
> >>
> >> Log is here (shorter ;) : https://paste.debian.net/1206278/
> > No additional range requests now, though still looks limited by
> > the client.  Any antivirus/firewall on the client (or on the
> > server)?
> 
> No. I have not soon understood the interest of a firewall : either the 
> port is closed and  I do not see the interest, either it is open and I 
> can only trust the application which manages it...
> 
> All my clients are debian and have no antivirus or firewall and tests 
> are done in the room where is the server.
> 
> nginx is in a lxd container with snap.

Ok, so it does not seem to be the client issue, yet for some 
reason nginx cannot proceed with sending data to the client as if 
network speed was severely limited.

Is sshd you test against in the same lxd container?  Any resource 
limits applied to the container?  What happens when you run nginx 
on the host system instead?

[...]

> Time out seem to occur :
> 
> 2021/08/02 14:39:10 [debug] 17204#17204: *22637 event timer add: 26: 
> 60000:7599423246
> 2021/08/02 14:39:15 [debug] 17204#17204: *22637 http run request: "/ggg?"

These aren't timeouts, but debug log lines: first says that nginx 
armed a timer for 60 seconds, and second one is about starting 
request processing 5 seconds later.  Debug logging is not 
configured at the global level and hence there is no debug logs 
about event processing, but it is nevertheless clear that the 
request processing was started due to an event reported by epoll() 
rather than due to a timeout.

-- 
Maxim Dounin
http://mdounin.ru/