Using NGINX Plus to Reduce the Frequency of Configuration Reloads

dynamic-upstream-configuration.conf

# This NGINX Plus configuration implements route-based session persistence 
# and enables the NGINX Plus API. Because the NGINX Plus API is used to 
# dynamically configure the servers in the upstream group, servers are not 
# defined statically in this file.

# To add an upstream server, run this command, replacing 
# <IP-ADDRESS:PORT> and <API-VERSION> with appropriate values:
#
#    curl -sX POST -d '{"server":"<IP-ADDRESS:PORT>", "route":"www.example.com"}' http://127.0.0.1:8888/api/<API-VERSION>/http/upstreams/vhosts/servers

# To remove an upstream server, first run this command to learn its internal 
# ID, as reported in the 'id' field:
#
#    curl -s http://127.0.0.1:8888/api/<API-version>/http/upstreams/vhosts/servers | jq -c '.peers[] | {server: .server, id: .id}'
#
# Then run this command to remove the server:
#
#    curl -sX DELETE http://127.0.0.1:8888/api/version/http/upstreams/vhosts/servers/<SERVER-ID>

# For more information, see the blog post associated with this file:
#    https://www.nginx.com/blog/using-nginx-plus-to-reduce-the-frequency-of-configuration-reloads/


user nginx;
worker_processes auto;

events {
    worker_connections 1024;
}

http {
    upstream vhosts {
        # Shared memory zone for state information about servers in        
        # the upstream group
        zone vhosts 128k;

        # Route-based session persistence based on the 'Host' header
        sticky route $http_host; 
	
        # There are no 'server' directives here because upstream 
        # servers are configured dynamically with the NGINX Plus API.
    }

    server {
        # Production frontend listening on standard HTTP port
        listen 80;

        # Enables collection of metrics for 'vhosts' upstream group
        status_zone vhosts; 

        location / {
            proxy_pass http://vhosts;
            proxy_set_header Host $http_host;
        }
    }

    server {
        # Dedicated server for upstream management with separate port 
        # that can be secured by a firewall      
        listen 8080;

        # Additional security for the management server
        allow 10.0.0.0/24; 
        allow 127.0.0.1/32;
        deny all;

        # Location of NGINX Plus static files
        root /usr/share/nginx/html; 
	
        # Enables the NGINX Plus API 
        location /api {
            api write=on; 
        }

        # HTML page for NGINX Plus dashboard
        location = /dashboard.html { } 
        
        # Route requests for / to the dashboard
        location = / {
            return 301 /dashboard.html;
        }
        
        # Redirect requests made to the pre-R14 dashboard
        location = /status.html {
            return 301 /dashboard.html;
        }
    }
}

# vim: syntax=nginx

frequent-reloads.conf

# The configuration in this file can be used to illustrate the effect of 
# frequently reloading the NGINX configuration under conditions of high load.
# New nginx worker processes are started to use the newly loaded configuration,
# but existing worker processes continue to run until established 
# connections can be terminated. Large numbers of worker processes can use 
# excessive memory and eventually cause system overload.

# As discussed on our blog
#
#   https://www.nginx.com/blog/using-nginx-plus-to-reduce-the-frequency-of-configuration-reloads/
#
# using the NGINX Plus API to dynamically reconfigure the servers in upstream
# groups is one way to reduce the frequency of reloads.

# To simulate the negative effects of frequent reloads:

# 1) Run nginx with this configuration file, and display the process list:
#
#     ps ax | grep nginx

# 2) Generate several requests, each of which takes about a minute:
#
#     curl -v http://localhost/ & curl -v http://localhost/ & curl -v http://localhost/ & curl -v http://localhost/

# 3) While the requests are processing, reload the configuration:
#
#     nginx -s reload

# 4) Display the process list. There are likely to be a number of processes in 
#    the "shutting down" state:
#
#     ps ax | grep nginx
#      1304 ?        S      0:00  \_ nginx: worker process is shutting down

user nginx;
worker_processes 8;

events {
    worker_connections 2014;
}

http {
    default_type text/plain;
    tcp_nodelay on;
    server {
        listen 8081;
        return 200 "Server $server_addr:$server_port\n\nTime: $time_local\n\n
Syntax:	  proxy_limit_rate rate;
Default:  proxy_limit_rate 0;
Context:  http, server, location

Limits how quickly the response from the
proxied server is read, in bytes per second.
The limit applies to each request, so if a worker
process simultaneously opens two connections to a 
proxied server, the overall rate is twice the 
specified limit. 
The default value of 0 (zero) disables rate limiting.
The directive is effective only if buffering of 
responses from the proxied server is enabled, 
which it is by default (controlled by the 
'proxy_buffering on' directive.)
        ";
    }

    upstream backend {
        zone backend 64k;
        server 127.0.0.1:8081;
    }
    
    server {
        listen 80 reuseport; # Hint: test with and without the reuseport parameter
        proxy_limit_rate 20; # Limit rate to 20 bps to emulate long-lived connections

        location / {
            proxy_pass http://backend;
        }
    }
}

# vim: syntax=nginx

For a discussion of these files, see Using NGINX Plus to Reduce the Frequency of Configuration Reloads