id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
1037	NGiNX drops the body of a HTTP proxy response on Linux if proxy doesn't read all content sent to it.	bbain.atlassian.com@…		"We have NGiNX sitting in front of gnuicorn on Linux. We have a REST resource that completely ignores the body of the request and returns a response and closes the connection. NGiNX returns the body of this resource if the size of proxy request sent (i.e. the bytes written to the socket) to gunicorn is <= 8k. If the request is >8k we end up with a HTTP response without the body.

I am pretty sure I have tracked this down. Linux will report a ECONNRESET error you try and read data on a socket that has been closed but still has outgoing data pending [http://stackoverflow.com/questions/2974021/what-does-econnreset-mean-in-the-context-of-an-af-local-socket]. So basically:

1. Client makes connection to NGiNX. 
2. NGiNX send >8k worth of data to Gunicorn.
3. Gunicorn reads in 8k to parse the headers. This leaves data on the socket.
4. Gunicorn sends response and closes the socket leaving some data still unread.
5. NGiNX gets all the response from Gunicorn.
6. NGiNX gets an ECONNRESET on the next recv call.
7. NGiNX assumes an error even though it has a complete response from Gunicorn and decides to only send part of the response.

The request works if in step 2 <= 8k is sent to gunicorn. In this case gunicorn will actually read all the data on the socket in its attempt to parse the headers. 

I tested on my Linux VM with both 1.6.2 and 1.11.3 (which I compiled with --with-debug). This is also occurring on our production servers where we have 1.6.2 deployed. 

Our setup has a unix socket between NGiNX and Gunicorn (though it also happens when using TCP sockets too). I have attached a simple test case to reproduce the problem."	defect	closed	minor		nginx-module	1.6.x	fixed	http proxy		"Linux bbainfedora 4.6.4-301.fc24.x86_64 #1 SMP Tue Jul 12 11:50:00 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
"	"nginx version: nginx/1.11.3
built by gcc 6.1.1 20160621 (Red Hat 6.1.1-3) (GCC) 
built with OpenSSL 1.0.2h-fips  3 May 2016
TLS SNI support enabled
configure arguments: --with-http_ssl_module --with-http_realip_module --with-http_addition_module --with-http_sub_module --with-http_dav_module --with-http_flv_module --with-http_mp4_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_random_index_module --with-http_secure_link_module --with-http_stub_status_module --with-http_auth_request_module --with-http_geoip_module --with-pcre-jit --with-mail --with-mail_ssl_module --with-file-aio --with-ipv6 --with-cc-opt='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic' --prefix=/home/bbain/nginx/1.11.3 --with-debug
"