Nginx 1.12.1 Memory Consumption

[Matthew Smith]

Hello,

I have encountered what I consider to be an interesting behavior. We have
Nginx 1.12.1 configured to do SSL termination as well as reverse proxy.
Whenever there is a traffic spike (300 req/s > 1000 req/s, 3k active
connections > 20k active connections), there is a corresponding spike in
Nginx memory consumption. In this case 500M > 8G across 10 worker
processes. What is interesting is that Nginx never seems to release this
memory after the traffic returns to normal. Is this expected? What is Nginx
using this memory for? Is there a configuration that will rotate the
workers based on some metric in order to return memory to the system?

Requests per second:
https://www.dropbox.com/s/cl2yqdxgqk2fn89/Screenshot%202018-03-14%2012.38.10.png?dl=0

Active connections:
https://www.dropbox.com/s/s3j4oux77op3svo/Screenshot%202018-03-14%2012.44.14.png?dl=0

Total Nginx memory usage:
https://www.dropbox.com/s/ihp5zxky2mgd2hr/Screenshot%202018-03-14%2012.44.43.png?dl=0

Thanks,

Matt
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