Advanced Openresty health check for multiple backends using LUA (full example)

nginx.conf

upstream other_backend {
    server 127.0.0.1:8080;
}
upstream main_backend {
    server 127.0.0.1:80;
}

server {
    listen 443 ssl http2;
    server_name example.com
    
    # …some other settings…

    location / {
        proxy_pass http://main_backend;
    }

    location = /other {
        proxy_pass http://other_backend;
    }

    location = /healthcheck {
        access_by_lua_block {
            local http = require "resty.http"
            local h = http.new()
            h:set_timeout(2 * 1000)
            local url = "http://127.0.0.1:18086/ping"
            local res, err = h:request_uri(url, {method = "GET"})
            if err or not res or res.status ~= 204 then
                ngx.status = ngx.HTTP_SERVICE_UNAVAILABLE
                ngx.exit(ngx.HTTP_OK)
            end
            url = "http://127.0.0.1:9096/ping"
            res, err = h:request_uri(url, {method = "GET"})
            if err or not res or res.status ~= 200 then
                ngx.status = ngx.HTTP_SERVICE_UNAVAILABLE
            end
            ngx.exit(ngx.HTTP_OK)
        }
    }
}