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Normal memory usage for SSL terminating, reverse proxy nginx?

May 27, 2016 03:15AM
It has been a difficult topic to research. The nginx instance is doing nothing more than what the subject stated. It reverse proxies to a backend, load balanced set of web app instances and terminates SSL for a large number of unique domains each with their own SSL cert. Here's a `ps aux` of nginx running after a clean start and zero (out of rotation) traffic.

root 20 0 676052 598224 1848 S 0.0 16.5 0:00.06 nginx
nginx 20 0 675552 597204 1228 S 0.0 16.5 0:00.44 nginx
nginx 20 0 675552 596612 636 S 0.0 16.5 0:00.36 nginx

Looking at that process list, nginx is using about 676mb of RAM for ~400 vhosts each with their own unique SSL cert for a unique domain. Here's an example of a vhost server config. They're all generated based on the same base template:

server {
listen 443 ssl proxy_protocol;
server_name <uniquehostname> www.<uniquehostname>;
access_log /var/log/nginx/access_vhost_443.log accesslog;
error_log /var/log/nginx/error_vhost_443.log warn;
real_ip_header proxy_protocol;

ssl on;
ssl_certificate /etc/nginx/ssl/<uniquehostname>/<uniquehostname>.crt;
ssl_certificate_key /etc/nginx/ssl/<uniquehostname>/<uniquehostname>.key;

ssl_stapling on;
ssl_stapling_verify on;

resolver internal-dns.vpc valid=60s;

set $internal "upstream-load-balancer.vpc";
location / {
if ($denied) {
return 444;
proxy_pass http://$internal;

Now, this wouldn't be all that bad. 1.69mb of memory per vhost isn't horrible, high, but not unsustainable. However, if I do `nginx -s reload` or restart via systemd service...

root 20 0 1370188 1.176g 3240 S 0.0 33.4 0:14.98 nginx
nginx 20 0 1370192 1.175g 2584 S 0.3 33.4 2:39.95 nginx
nginx 20 0 1370192 1.175g 2584 S 1.7 33.4 2:28.42 nginx

It doubles the memory consumption! It never goes up or down drastically again. It's as if it duplicates and never frees or releases unless you do a restart.

This was tested on a handful of AWS EC2 instance types using vanilla Centos7 and both nginx 1.6.3 (stable in centos repos) and nginx 1.10.0 (nginx.org repo).

In summary, my questions are thus:
- Is it normal for nginx to use ~1.7mb per SSL vhost?
- Is there a way to reduce that memory usage?

- Am I the only one that experiences the doubling of nginx memory usage after a nginx reload?
- Is that a bug?

Subject Author Posted

Normal memory usage for SSL terminating, reverse proxy nginx?

onecrazymonkey May 27, 2016 03:15AM

Re: Normal memory usage for SSL terminating, reverse proxy nginx?

Maxim Dounin May 27, 2016 10:00AM

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