Nginx stops sending file after ~1.5mb ?
Igor Sysoev
is at rambler-co.ru
Sun Jan 25 20:33:26 MSK 2009
On Sun, Jan 25, 2009 at 06:26:58PM +0200, Yo'av Moshe wrote:
> Igor, I tried using select instead of poll, but I get the exact same
> problem.
>
> Check my strace:
> http://pastebin.com/m65056ec0
>
> I get the same thing with rtsig too.
>
> Hints?
> Again, file is at http://www.noal.org.il/static/temp/hozer.pdf. Server is
> using select now.
According strace select() does not return event for socket 19 after
sendfile64() sent 1651005 bytes:
25951 18:14:26 select(20, [7 8 16 19], [19], NULL, {60, 0} <unfinished ...>
25951 18:14:27 <... select resumed> ) = 1 (out [19], left {58, 790000})
25951 18:14:27 gettimeofday({1232900067, 890376}, NULL) = 0
25951 18:14:27 sendfile64(19, 20, [1509465], 440765 <unfinished ...>
25951 18:14:27 <... sendfile64 resumed> ) = 141540
25951 18:14:27 sendfile64(19, 20, [1651005], 299225 <unfinished ...>
25951 18:14:27 <... sendfile64 resumed> ) = -1 EAGAIN (Resource temporarily unavailable)
25951 18:14:27 select(20, [16 19], [19], NULL, {0, 500000} <unfinished ...>
25951 18:14:28 <... select resumed> ) = 0 (Timeout)
As you have got the same issue with all methods (even with level triggered
select()), I believe that the bug is in sendfile. You may try to turn
it off even for the single file:
location = /static/temp/hozer.pdf {
sendfile off;
}
In Linux 2.6.23 sendfile() has been rewritten to use splice framework.
The bug may be introduced while rewriting.
BTW, it seems that thttpd does not use sendfile.
> Thanks...
> Yo'av.
>
> On Fri, Jan 23, 2009 at 3:05 PM, Igor Sysoev <is at rambler-co.ru> wrote:
>
> > On Fri, Jan 23, 2009 at 02:35:00PM +0200, Yo'av Moshe wrote:
> >
> > > Thanks Igor.
> > > I don't want to be rude, but I find it hard to believe that it's a kernel
> > > bug.
> > >
> > > First, I'm using the default CentOS 5.2 kernel, it's seems to me pretty
> > odd
> > > that there's such a bug in it. CentOS is being used on a lot of servers,
> > > some of them must be running nginx.
> > >
> > > Second, I tried serving the same file with thttpd, and it runs just fine.
> > > http://195.28.180.147:40/temp/hozer.pdf
> > > Note it's the exact same file which I cannot get from nginx:
> > > http://www.noal.org.il/static/temp/hozer.pdf
> > >
> > > How come thttpd can serve the file just fine? If it's a kernel bug, I
> > > thought it would happen with all of my servers.
> > > If it's using some different way of sending the files which does not
> > depend
> > > on that epoll call - is there any way to configure nginx to use that as
> > > well?
> >
> > I do not look modern thttpd, but according its change log, it has no
> > epoll support. You may try different ways in nginx: you need to build it
> >
> > --with-rtsig_module
> > --with-select_module
> > --with-poll_module
> >
> > and then choose method:
> >
> > events {
> > use select;
> > #use poll;
> > #use rtsig;
> > }
> >
> > Also, epoll has two modes: level triggered (default) and edge
> > triggered (EPOLLET). nginx uses more effective edge triggered mode,
> > lighttpd uses level triggered one. The bug may be in ET mode only.
> >
> > As to probabilty of kernel bugs: I saw them in FreeBSD (kqueue, sendfile),
> > Linux (epoll), Solaris (event ports), and MacOSX (kqueue, sendfile).
> >
> > > Can I do anything to confirm that it's a kernel bug? If it is, I should
> > > probably contact CentOS's maintainers.
> >
> > Your straces confirms this: nginx added socket to epoll and did not
> > deleted it, nevertheless epoll does not send event.
> >
> > > Thank you, again.
> > > Yo'av.
> > >
> > > On Wed, Jan 21, 2009 at 7:26 AM, Igor Sysoev <is at rambler-co.ru> wrote:
> > >
> > > > On Wed, Jan 21, 2009 at 01:52:53AM +0200, Yo'av Moshe wrote:
> > > >
> > > > > Igor, here's the new strace.
> > > > > http://pastebin.com/m5129c54b
> > > > >
> > > > > Does the fact it works in low download rates still makes you think
> > it's a
> > > > > kernel issue?
> > > >
> > > > Yes, this is seems like a kernel issue. Kernel excatly said (with
> > EAGAIN)
> > > > that there is no place to output data, but never returned a new
> > > > notification
> > > > via epoll_wait() about free space:
> > > >
> > > > 21420 01:39:43 <... epoll_wait resumed> {{EPOLLOUT, {u32=153137960,
> > > > u64=13811628390360331048}}}, 512, 60000) = 1
> > > > 21420 01:39:43 gettimeofday({1232494783, 413764}, NULL) = 0
> > > > 21420 01:39:43 sendfile64(20, 21, [1645625], 304605) = 40320
> > > > 21420 01:39:43 sendfile64(20, 21, [1685945], 264285) = -1 EAGAIN
> > (Resource
> > > > temporarily unavailable)
> > > > 21420 01:39:43 epoll_wait(11, <unfinished ...>
> > > >
> > > > This is probably some race condition inside kernel, that does not
> > appear on
> > > > low speed download.
> > > >
> > > > > Thank you, really!
> > > > > And thanks, Kiril and Jeff, for confirming that!
> > > > >
> > > > > Yo'av.
> > > > >
> > > > >
> > > > > On Tue, Jan 20, 2009 at 9:39 PM, Kiril Angov <kupokomapa at gmail.com>
> > > > wrote:
> > > > >
> > > > > > wget http://www.noal.org.il/static/temp/barvazi2.pdf
> > > > > > --2009-01-20 21:36:00--
> > > > http://www.noal.org.il/static/temp/barvazi2.pdf
> > > > > > Resolving www.noal.org.il... 195.28.180.147
> > > > > > Connecting to www.noal.org.il|195.28.180.147|:80... connected.
> > > > > > HTTP request sent, awaiting response... 200 OK
> > > > > > Length: 1950230 (1.9M) [application/pdf]
> > > > > > Saving to: `barvazi2.pdf'
> > > > > >
> > > > > > 81% [=====================================> ] 1,596,665
> > > > > > --.-K/s eta 5s
> > > > > >
> > > > > >
> > > > > > wget -c http://www.noal.org.il/static/temp/barvazi2.pdf
> > > > > > --2009-01-20 21:38:28--
> > > > > > http://www.noal.org.il/static/temp/barvazi2.pdf
> > > > > > Resolving www.noal.org.il... 195.28.180.147
> > > > > > Connecting to www.noal.org.il|195.28.180.147|:80... connected.
> > > > > > HTTP request sent, awaiting response... 206 Partial Content
> > > > > > Length: 1950230 (1.9M), 305960 (299K) remaining [application/pdf]
> > > > > > Saving to: `barvazi2.pdf'
> > > > > >
> > > > > > 100%[+++++++++++++++++++++++++++++++++++++++=======>] 1,950,230
> > > > > > 295K/s in 1.0s
> > > > > >
> > > > > > 2009-01-20 21:38:30 (295 KB/s) - `barvazi2.pdf' saved
> > [1950230/1950230]
> > > > > >
> > > > > >
> > > > > > On Tue, Jan 20, 2009 at 9:31 PM, jeff emminger <
> > jemminger at gmail.com>
> > > > > > wrote:
> > > > > > >> Could anyone confirm that this works:
> > > > > > >> wget --limit-rate=3500
> > > > http://www.noal.org.il/static/temp/barvazi2.pdf
> > > > > > >> while this doesn't:
> > > > > > >> wget http://www.noal.org.il/static/temp/barvazi2.pdf
> > > > > > >>
> > > > > > >
> > > > > > > Confirmed
> > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > > --
> > > > > Yo'av Moshe
> > > >
> > > > --
> > > > Igor Sysoev
> > > > http://sysoev.ru/en/
> > > >
> > > >
> > >
> > >
> > > --
> > > Yo'av Moshe
> >
> > --
> > Igor Sysoev
> > http://sysoev.ru/en/
> >
> >
>
>
> --
> Yo'av Moshe
--
Igor Sysoev
http://sysoev.ru/en/
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