Nginx find in json deviceID for sharding

jparseuuid.lua

if ngx.req.get_method() ~= "POST" then
  return
end
-- read request body
ngx.req.read_body()
local data = ngx.req.get_body_data()
-- regexp
if  data then
    local f = string.match(data,ngx.var.MATH_REGEXP)
    if f then
        -- Set Var to Nginx
        ngx.var.UUID = f;
    end
end
-- Dump
ngx.say("Hello <b>world</b>! UUID = " .. ngx.var.UUID);

nginx.conf

#user  www-data;
worker_processes  1;
worker_priority 1;
worker_rlimit_nofile 1000;
timer_resolution 100ms;
daemon off;
master_process on;
error_log  /tmp/nginx-error.log;
#pid        /var/run/nginx.pid;
events {
    worker_connections  256;
}
http {

    access_log /tmp/nginx-access.main.log;
    error_log  /tmp/nginx-error.main.log;


server {
  set $UUID false;


  location /hello {

    set $MATH_REGEXP "\"deviceID\":\"([^\"]+)\"";

    client_body_buffer_size 3M;
    client_max_body_size  3M;
    content_by_lua_file /tmp/nginx/jparseuuid.lua;
    if ($UUID != false )
    {
       # use `upstream->hash $UUID`;
    }
  }
}

}

req.bash

curl http://localhost:8000/hello --data '{"username":"xyz","deviceID":"qew-ew-wee2qwe1","2323":"23"}'