Nginx stops sending file after ~1.5mb ?

Yo'av Moshe bjesus at gmail.com
Sun Jan 25 22:04:54 MSK 2009 

Sendfile is now off, using select, and still the same...
http://pastebin.com/m2c3ea25b

Yo'av

On Sun, Jan 25, 2009 at 7:33 PM, Igor Sysoev <is at rambler-co.ru> wrote:

> 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/
>
>


-- 
Yo'av Moshe
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