Nginx unable to resolve IP Addresse set using lua plugin

Question

I have setup nginx as a proxy server. It should basically forward the HTTP URL to particular IP address. The following is my configuration

worker_processes  1;
error_log logs/error.log;
events {
    worker_connections 1024;
}
http {
server {
        listen 8080;
        location ~ ^/db/([-_a-zA-Z0-9/]+)/series {
set $token $1 ;
            set $upstream1 " ";
            content_by_lua 'length = string.len(ngx.var.token)
                if length < 8 then 
                    ngx.say("Invalid token (less than 8 characters)")
                    return
                end
                local count = 0
                for i=1,8 do 
                    count = count + string.byte(ngx.var.token,i)
                end
              in_server = {
                    [0] = "10.0.0.1:8086",
                    [1] = "10.0.0.2:8086",
                    [2] = "10.0.0.3:8086",
                    [3] = "10.0.0.4:8086",
                    [4] = "10.0.0.5:8086",
                    [5] = "10.0.0.6:8086",
                    [6] = "10.0.0.7:8086",
                    [7] = "10.0.0.8:8086" 
            }
            ngx.var.upstream1 = in_server[count%7]
';
            proxy_pass http://$upstream1;
        }

    }
}

The upstream variable is set to an IP address based on the type of token. The logic is sound, I have tested in lua separately. But everytime I query nginx server , I get the following error :

2016/05/09 17:20:20 [error] 32680#0: *1 no resolver defined to resolve  , client: 127.0.0.1, server: , request: "GET /db/rustytoken/series?&q=select%20%2A%20from%20foo%20limit%201 HTTP/1.1", host: "localhost:8080"

I am not sure, why does it need a resolver If am sending a direct IP Address. Anyways, I added the following in location directive

resolver 127.0.0.1

And installed dnsmasq to resolve domain names. It still couldnt. I get the following error instead.

2016/05/09 17:14:22 [error] 32030#0: *1   could not be resolved (3: Host not found), client: 127.0.0.1, server: , request: "GET /db/rustytoken/series?q=select%20%2A%20from%20foo%20limit%201 HTTP/1.1", host: "localhost:8080"

score 1 · Answer 1 · answered May 11 '16 at 07:14

1

You should use "rewrite_by_lua" instead of "content_by_lua" because you set $upstream1 " " , so you have to rewrite it.

answered May 11 '16 at 07:14

huyhoang

53
5

Alexander Altshuler · Answer 2 · 2016-05-11T08:22:42.003

You shoud use https://github.com/openresty/lua-nginx-module#balancer_by_lua_block instead of content_by_lua. See some examples here https://github.com/openresty/lua-resty-core/blob/master/lib/ngx/balancer.md

Nginx config is not executed linearly. Here is the best tutorial I know - http://openresty.org/download/agentzh-nginx-tutorials-en.html

Update

Another possible solution:

set_by_lua_block $upstream1 {
       length = string.len(ngx.var.token)
       if length < 8 then 
             -- cannot use this API here, you should add error processing
             --ngx.say("Invalid token (less than 8 characters)")
             return
       end
       local count = 0
       for i=1,8 do 
            count = count + string.byte(ngx.var.token,i)
       end
       in_server = {
            [0] = "10.0.0.1:8086",
            [1] = "10.0.0.2:8086",
            [2] = "10.0.0.3:8086",
            [3] = "10.0.0.4:8086",
            [4] = "10.0.0.5:8086",
            [5] = "10.0.0.6:8086",
            [6] = "10.0.0.7:8086",
            [7] = "10.0.0.8:8086" 
       }
       return in_server[count%7]
}

Nginx unable to resolve IP Addresse set using lua plugin

2 Answers2