A simple dynamic request router for nginx. Pluggable backends for flexibility; ngx.shared.DICT caching for performance.
Install openresty and put lua-resty-router in lualib. Install and run the following nginx.conf:
worker_processes 2;
error_log logs/error.log info;
events {
worker_connections 1024;
}
http {
lua_shared_dict locks 1m;
lua_shared_dict cache_dict 1m;
lua_package_path "/usr/local/openresty-debug/lualib/?.lua;/usr/local/openresty/lualib/?.lua;;";
lua_package_cpath "/usr/local/openresty-debug/lualib/?.so;/usr/local/openresty/lualib/?.so;;";
server {
listen 8888;
location / {
set $rr_route '';
set $rr_status 'NOTFOUND';
rewrite_by_lua '
local router = require "resty.router"
local r = router:new(
"resty.router.dns",
{
dns_opts = {
nameservers = { "8.8.8.8" }
}
}
)
local route = r:get_route(ngx.var.arg_host)
if not route then
return ngx.exit(404)
end
ngx.var.rr_route = route
ngx.var.rr_status = ngx.ctx.shcache["resty_router_cache"].cache_status
';
more_set_headers "X-RR-Key: $arg_host";
more_set_headers "X-RR-State: $rr_status";
more_set_headers "X-RR-Route: $rr_route";
proxy_pass http://$rr_route;
}
}
}
This example uses the host arg as the key, but could just as easily use any HTTP header, host, or path part.
curl -I http://localhost:8888/?host=example.com
A more inventive approach for a microservices architecture is to use SRV records alongside a same-named record for the router. The careful reader will note our SRV record format is wanting a prefix like "_Service._Proto.". For applications using private DNS this seems unnecessary.
# example-service.example.com IN CNAME router.example.com.
# example-service.example.com IN SRV 1 1 5000 10.1.1.1
# example-service.example.com IN SRV 1 1 5000 10.1.1.2
# example-service.example.com IN SRV 1 1 5000 10.1.1.3
...
location / {
set $rr_route '';
set $rr_status 'NOTFOUND';
rewrite_by_lua '
local router = require "resty.router"
local dns = require "resty.dns.resolver"
local r = router:new(
"resty.router.dns",
{
dns_opts = {
nameservers = { "8.8.8.8" },
qtype = dns.TYPE_SRV
}
}
)
local route = r:get_route(ngx.var.http_host)
if not route then
return ngx.exit(404)
end
ngx.var.rr_route = route
ngx.var.rr_status = ngx.ctx.shcache["resty_router_cache"].cache_status
';
more_set_headers "X-RR-Key: $arg_host";
more_set_headers "X-RR-State: $rr_status";
more_set_headers "X-RR-Route: $rr_route";
proxy_pass http://$rr_route;
}
...
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