nginx memory leak URL with large cookies and connections with long keepalive_requests

[2clarkd@…]

*summary*: Persisting upstream connections for a large number of transactions with attribute "keepalive_requests 100000" tends to leak memory rapidly with large URL cookies (ie. > 512 characters).
*impact*: memory not freed until large transaction count completes. Cookies leaked in memory pool for re-used connection may be security risk.
*workaround*: reduce the keepalive_requests to smaller value (default 100). (minimizes size of leak as connection reset clears memory usage)
*topics*; memory leak, large URL cookies, keepalive_requests,
*configuration*;

sample URL
sample URL command (note cookie text suppressed, likely any 512-1024 byte string will do in one or more cookie variables)
curl --cookie "cookie1=1234567890....; cookie2=abcd...; " "​http://adevhost/apath/?var1=xyz&var2=abc&var3=zyx

cat nginx_leak.conf

worker_processes auto;
worker_rlimit_nofile 100000; exacerbates leak

events {

worker_connections 65536;
# optimized to serve many clients with each thread, essential for linux
use epoll;
# accept as many connections as possible
multi_accept on;

}

http {

include /etc/nginx/mime.types;
default_type application/octet-stream;

# access_log /var/log/nginx/access.log main;
rewrite_log on;

keepalive_timeout 30s;
keepalive_requests 100000;

proxy_connect_timeout 15s;
proxy_send_timeout 15s;
proxy_read_timeout 15s;
client_body_timeout 15s;
client_header_timeout 15s;
send_timeout 15s;

expires off;
proxy_http_version 1.1;
proxy_cache_bypass 1;

proxy_no_cache 1;
proxy_set_header Connection "";

proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;

# include /etc/nginx/conf.d/*.conf;
# added here for simplification

upstream upstream_leak {

keepalive 300;
server 127.0.0.1:8080;

}

server {

listen 80 backlog=1280 default_server ipv6only=off;
server_name $hostname;

location ~* \.(sfx)$ {

proxy_pass ​http://upstream_leak;
break;

}
location ~ / {

return 403;

}

}

add_header Connection "keep-alive";
add_header Keep-Alive "timeout=15";

}