Nginx stops sending file after ~1.5mb ?

Yo'av Moshe bjesus at gmail.com
Tue Jan 27 12:25:09 MSK 2009 

Sure, here my Cherokee's strace:
http://pastebin.com/m13cd213d

What you are saying about tcpdump's logs is strange, but I have no idea
what's causing it.

Yo'av.

On Tue, Jan 27, 2009 at 10:51 AM, Igor Sysoev <is at rambler-co.ru> wrote:

> On Tue, Jan 27, 2009 at 10:42:57AM +0200, Yo'av Moshe wrote:
>
> > Note I just compiled Cherokee 0.98. It is serving the file as it should
> > using sendfile and epoll.
>
> Have you tried this on the same host ?
> Could you post strace ?
>
> > On Mon, Jan 26, 2009 at 2:05 PM, Yo'av Moshe <bjesus at gmail.com> wrote:
> >
> > > Hey, attached is my tcpdump log.
> > > I've never used tcpdump before, so I hope the log is fine.
> > > I used grep to show only the connections from my computer while running
> > > 'wget http://www.noal.org.il/static/temp/hozer.pdf'.
> > >
> > > Hope this will lead us somewhere...
> > >
> > > Yo'av.
> > >
> > >
> > > On Sun, Jan 25, 2009 at 9:21 PM, Igor Sysoev <is at rambler-co.ru> wrote:
> > >
> > >> On Sun, Jan 25, 2009 at 09:04:54PM +0200, Yo'av Moshe wrote:
> > >>
> > >> > Sendfile is now off, using select, and still the same...
> > >> > http://pastebin.com/m2c3ea25b
> > >>
> > >> I have no idea, why it may be so.
> > >>
> > >> I see that select() returned event ("out [19]"):
> > >>
> > >> 28215 20:50:18 select(20, [10 19], [19], NULL, {0, 500000} <unfinished
> > >> ...>
> > >> 28215 20:50:18 <... select resumed> )   = 1 (out [19], left {0,
> 380000})
> > >>
> > >> However, at some stage select() did not return event, although the
> event
> > >> is still active ("select(20, [10 19], [19], NULL ..."):
> > >>
> > >> 28215 20:50:18 gettimeofday({1232909418, 293895}, NULL) = 0
> > >> 28215 20:50:18 writev(19,
> > >>
> [{"\227\1\2\1\3\1\4\1\5\0\373\0\374\1\230\1\231\1\232\1\233\0\375\0\376\1\6\1\7\1\10\0"...,
> > >> 9676}], 1) = 9676
> > >> 28215 20:50:18 pread64(20,
> > >>
> "\24\7\6#\"\'&\0214\22$63\1\6\25\24\26\27\02632654&#\"\6\3\226\204"...,
> > >> 32768, 1605632) = 32768
> > >> 28215 20:50:18 writev(19,
> > >>
> [{"\24\7\6#\"\'&\0214\22$63\1\6\25\24\26\27\02632654&#\"\6\3\226\204"...,
> > >> 32768}], 1) = 32768
> > >> 28215 20:50:18 pread64(20, "\0 \0M\0o\0r\0i\0s\0o\0n\0\'\0s\0
> > >> \0d\0i\0r\0e\0c"..., 32768, 1638400) = 32768
> > >> 28215 20:50:18 writev(19, [{"\0 \0M\0o\0r\0i\0s\0o\0n\0\'\0s\0
> > >> \0d\0i\0r\0e\0c"..., 32768}], 1) = 1716
> > >> 28215 20:50:18 select(20, [10 19], [19], NULL, {0, 500000} <unfinished
> > >> ...>
> > >> 28215 20:50:18 <... select resumed> )   = 0 (Timeout)
> > >>
> > >> Could you run tcpdump of the session ?
> > >>
> > >> > 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
> > >>
> > >> --
> > >> Igor Sysoev
> > >> http://sysoev.ru/en/
> > >>
> > >>
> > >
> > >
> > > --
> > > Yo'av Moshe
> > >
> >
> >
> >
> > --
> > Yo'av Moshe
>
> --
> Igor Sysoev
> http://sysoev.ru/en/
>
>


-- 
Yo'av Moshe
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