id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
486	ngx_http_upstream module lack the check of broken peer connection before using it	marc li		"HI, guys, 
ngx_http_upstream module use ngx_http_upstream_test_connect in order to valid connection, however for keepalived upstream connection which may be closed before the test (ngx_http_upstream_keepalive_close_handler may not be triggered before peer.get pick it as the new connection), the test may not be adequate.

So i suggest that we do a MSG_PEEK in nix_http_upstream_test_connect as below:

diff -ur nginx-1.4.4/src/http/ngx_http_upstream.c nginx-1.4.4-local/src/http/ngx_http_upstream.c
--- nginx-1.4.4/src/http/ngx_http_upstream.c    2013-11-19 19:25:25.000000000 +0800
+++ nginx-1.4.4-local/src/http/ngx_http_upstream.c      2014-01-14 18:01:58.061499032 +0800
@@ -1886,6 +1886,22 @@
         }
     }
 
+    /*
+     * Maybe getsockopt is not enough, let's pick one byte from the connection
+     * To prevent broken keepalived conn from being used
+     */
+    char buf[1];
+    int n = recv(c->fd, buf, 1, MSG_PEEK);
+    err = ngx_socket_errno;
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, err,
+                   ""http upstream ngx_upstream_test_connect: %d"", n);
+
+    if (n == 0 ||
+        (n < 0 && err != NGX_EAGAIN)) {
+        return NGX_ERROR;
+    }
+
     return NGX_OK;
 }

3Q~~~"	defect	closed	minor		nginx-module	1.5.x	worksforme			Linux tcpper-vm 3.5.0-44-generic #67~precise1-Ubuntu SMP Wed Nov 13 16:16:57 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux	"nginx version: nginx/1.4.4
built by gcc 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) 
TLS SNI support enabled
configure arguments: --prefix=/home/tcpper/nginx --with-debug --with-pcre=../pcre-8.33 --with-pcre-jit --with-http_stub_status_module --with-http_gunzip_module --with-http_ssl_module --add-module=../ngx_devel_kit-0.2.19 --add-module=../lua-nginx-module-0.9.3 --add-module=../echo-nginx-module-0.48 --add-module=../ngx_pagespeed-1.7.30.1-beta --add-module=../upstream_jhash --without-http_ssi_module --without-http_userid_module --without-http_geo_module --without-http_map_module --without-http_split_clients_module --without-http_fastcgi_module --without-http_uwsgi_module --without-http_scgi_module --without-http_memcached_module --without-http_empty_gif_module --without-http_browser_module --with-ld-opt=-Wl,-rpath,/home/tcpper/luajit/lib"