lua-resty-memcached problem

apg · 2013-11-27T05:09:23+00:00

Thanks agentzh :)On Tuesday, November 26, 2013 4:37:52 AM UTC+5:30, agentzh wrote:Hello! On Mon, Nov 25, 2013 at 1:41 PM, ankit wrote: > Not sure w...

lua-resty-memcached problem

apg

Hey all,

I'm having a problem with the lua-resty-memcached client. The documentation seems to suggest that it will attempt to resolve hostnames[0], but I get this message in my log when I give it a hostname instead of an ip address:

2013/11/26 20:07:45 [error] 5873#0: *247 [lua] ratelimiter.lua:121: getclient(): failed to connect: no resolver defined to resolve "sup-el-6p6xcg7.bg.0001.use1.cache.amazonaws.com", client: 11.121.12.28, server: , request: ....

I've verified that it can be resolved on the server machine using the dns provided by /etc/resolv.conf. Here's the code that's attempting to resolve it:

function RateLimiter:getclient(key, ngx)
   local server = self.ring:get(key)
   if server then
      local memc, err = self.memcache:new{
         key_transform = { encoder.encode, encoder.decode }}
      if memc then
         memc:set_timeout(1) -- timeout *fast*
         local ok, err = memc:connect(server.host, server.port)
         if ok then
            return memc
         else
            ngx.log(ngx.ERR, "failed to connect: ", err) -- (this is the log line generated)
         end
      else
         ngx.log(ngx.ERR, "failed to instantiate memcached client: ", err)
      end
   end
   return nil
end

Nginx config is here:

    location / {
        access_by_lua '
           if not RL:passes(ngx) then
              ngx.header["X-Try-Again-In"] = tostring(60 - os.date("%s"))
              ngx.exit(ngx.HTTP_FORBIDDEN)
           end
        ';

proxy_pass http://backend;

}

I'm probably missing something simple. Anyone have any thoughts?

Thanks,

Andrew

[0]: "Before actually resolving the host name and connecting to the remote backend, this method will always look up the connection pool for matched idle connections created by previous calls of this method."

agentzh

Hello!

On Tue, Nov 26, 2013 at 1:09 PM, Andrew Gwozdziewycz wrote:
> I'm having a problem with the lua-resty-memcached client. The documentation
> seems to suggest that it will attempt to resolve hostnames[0],

Well, this has been an FAQ now :)

You need to configure the "resolver" directive in your nginx.conf properly, see

    http://nginx.org/en/docs/http/ngx_http_core_module.html#resolver

For example, we could use Google's free DNS nameserver by putting the
following line in nginx.conf:

    resolver 8.8.8.8;

ngx_lua's cosocket API uses Nginx's own (nonblocking) resolver implementation.

You can also check out the nameservers used by your current system by
checking out the file /etc/resolve.conf:

    $ cat /etc/resolv.conf
    # Generated by NetworkManager
    nameserver 8.8.8.8
    nameserver 8.8.4.4

This is the result on my laptop. As you can see, I'm using Google's
two DNS servers for my system resolver as well.

BTW, Nginx's own resolver does not support the /etc/hosts file (yet).
But it's not hard for you to look up this file in your Lua code
yourself ;)

Regards,
-agentzh

apg

Ooops. Thanks for the response. Sorry that I didn't see the FAQ (is there one yet?) beforehand!

On Tue, Nov 26, 2013 at 4:42 PM, Yichun Zhang (agentzh) <age...@gmail.com> wrote:

Hello!

On Tue, Nov 26, 2013 at 1:09 PM, Andrew Gwozdziewycz wrote:
> I'm having a problem with the lua-resty-memcached client. The documentation
> seems to suggest that it will attempt to resolve hostnames[0],

Well, this has been an FAQ now :)

You need to configure the "resolver" directive in your nginx.conf properly, see

http://nginx.org/en/docs/http/ngx_http_core_module.html#resolver

For example, we could use Google's free DNS nameserver by putting the
following line in nginx.conf:

resolver 8.8.8.8;

ngx_lua's cosocket API uses Nginx's own (nonblocking) resolver implementation.

You can also check out the nameservers used by your current system by
checking out the file /etc/resolve.conf:

$ cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 8.8.8.8
nameserver 8.8.4.4

This is the result on my laptop. As you can see, I'm using Google's
two DNS servers for my system resolver as well.

BTW, Nginx's own resolver does not support the /etc/hosts file (yet).
But it's not hard for you to look up this file in your Lua code
yourself ;)

Regards,
-agentzh
.

agentzh

Hello!

On Tue, Nov 26, 2013 at 1:52 PM, Andrew Gwozdziewycz wrote:
> Ooops. Thanks for the response. Sorry that I didn't see the FAQ (is there
> one yet?) beforehand!
>

There is no formal FAQ page yet. You're welcome to contribute one :)

I just meant it is an FAQ on the mailing lists :)

Regards,
-agentzh