How to dynamically add an upstream in Nginx? - nginx

Question

I mean add an upstream but not a server in an upstream.
That means I don't have an upstream block like:
upstream backend {
# ...
}
I want create an upstream block dynamically. That is something like:
content_by_lua_block {
upstream_block.add('backend');
upstream_block.add_server('backend', '127.0.0.1', 8080);
upstream_block.add_server('backend', '127.0.0.1', 8081);
upstream_block.add_server('backend', '127.0.0.1', 8082);
upstream_block.del_server('backend', '127.0.0.1', 8080);
}
proxy_pass http://backend

Answer 1

You may use balancer_by_lua* and https://github.com/openresty/lua-resty-core/blob/master/lib/ngx/balancer.md
You will have a full control which upstream is selected for given request.
You may self provision you code or use existing upstream config as the source using https://github.com/openresty/lua-upstream-nginx-module

Answer 2

I found a nginx module called ngx_http_dyups_module matches my question.

Answer 3

My example on how to dynamically add upstream servers based on CPU count.
Servers. I used openresty and configured it to listen on multiple ports.
worker_processes auto;
error_log logs/openresty.err ;
events {
worker_connections 1000;
}
http {
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log logs/openresty.log main;
server {
listen 127.0.0.1:8080;
listen 127.0.0.1:8081;
listen 127.0.0.1:8082;
listen 127.0.0.1:8083;
listen 127.0.0.1:8084;
listen 127.0.0.1:8085;
listen 127.0.0.1:8086;
listen 127.0.0.1:8087;
listen 127.0.0.1:8088;
listen 127.0.0.1:8089;
listen 127.0.0.1:8090;
server_name *.*;
location / {
content_by_lua_block {
--[[ local NumCores = tonumber(os.getenv("NUMBER_OF_PROCESSORS"))
local NumCores=10
]]
--
-- local f = io.popen("ps -ef | grep nginx | wc -l ")
local f = io.popen("/usr/sbin/sysctl -n hw.ncpu ")
ngx.print('CPU count: '..f:read())
f:close()
}
}
}
}
And the reverse proxy, dynamically add upstream servers based on CPU count.
error_log logs/reverse_openresty.err ;
events {
worker_connections 1000;
}
http {
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log logs/reverse_openresty.log main;
upstream backend {
server 0.0.0.1; # just an invalid address as a place holder
balancer_by_lua_block {
local balancer = require "ngx.balancer"
local start_port=8080
local f = io.popen("/usr/sbin/sysctl -n hw.ncpu ") -- get cpu count
local cpu_count=tonumber(f:read())
f:close()
local max_port=start_port+cpu_count-2
repeat
local ok, err = balancer.set_current_peer('127.0.0.1', start_port)
if not ok then
ngx.log(ngx.ERR, "failed to set the current peer: ", err)
return ngx.exit(500)
end
start_port=start_port+1
until start_port>max_port
}
keepalive 10; # connection pool
}
server {
listen 80;
location / {
proxy_redirect off;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header Host $http_host;
proxy_pass http://backend; # force using http. as node server.js only have http
}
}
}
The configuration is tested on MacOs.

Answer 4

I'm using ngx_dynamic_upstream. it's really good at production. i'd forked original from owner and checked source codes for just in case.