Nginx unable to resolve IP Addresse set using lua plugin - nginx

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"

Answer 1

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

Answer 2

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]
}