id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
1174	Partial downloads (sendfile)	pokotilenko@…		"I'm seeing partial downloads. Investigation come to nginx closing connection mid-file on ""client timed out (110: Connection timed out) while sending response to client"".

See attached portion of debug log. There is a sequence of sendfiles, delay, and a client timeout (send_timeout 150 during this capture).

I've been watching socket send buffer (netstat -ntp | grep nginx | grep CLIENT_IP). While download is progressing send buffer is non-zero, like this:

tcp 0 2944800 SERVER_IP:80 CLIENT_IP:60338 ESTABLISHED 30723/nginx: worker

When downloading hangs, send-buffer is zero like this:
tcp 0 0 SERVER_IP:80 CLIENT_IP:60476   ESTABLISHED 5247/nginx: worker

At this time no write event is happening and no more sendfiles tried.

On a server which is dedicated for testing this issue I can 100% reproduce this after flushing linux fs cache.

Either of those helps:
- sendfile off
- aio threads
- sendfile_max_chunk 128k

If I get it right, with ""aio off"" sendfile is blocking and regarding debug log it doesn't block for long, but it seems that under some condition the connection socket fd is not put to wait for output availability so no output (sendfile) happening.

I have tcp_nopush and tcp_nodelay enabled."	defect	closed	minor		nginx-core	1.10.x	fixed	sendfile partial download client timeout		Linux **** 4.4.0-45-generic #66-Ubuntu SMP Wed Oct 19 14:12:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux	"nginx version: nginx/1.10.0 (Ubuntu)
built with OpenSSL 1.0.2g  1 Mar 2016
TLS SNI support enabled
configure arguments: --with-cc-opt='-g -O2 -fPIE -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2' --with-ld-opt='-Wl,-Bsymbolic-functions -fPIE -pie -Wl,-z,relro -Wl,-z,now' --prefix=/usr/share/nginx --conf-path=/etc/nginx/nginx.conf --http-log-path=/var/log/nginx/access.log --error-log-path=/var/log/nginx/error.log --lock-path=/var/lock/nginx.lock --pid-path=/run/nginx.pid --http-client-body-temp-path=/var/lib/nginx/body --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-proxy-temp-path=/var/lib/nginx/proxy --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-debug --with-pcre-jit --with-ipv6 --with-http_ssl_module --with-http_stub_status_module --with-http_realip_module --with-http_auth_request_module --with-http_addition_module --with-http_dav_module --with-http_geoip_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_image_filter_module --with-http_v2_module --with-http_sub_module --with-http_xslt_module --with-stream --with-stream_ssl_module --with-mail --with-mail_ssl_module --with-threads"