woocommerce admin create order get customer id on create - php

Question

It's been a couple of days now, and I can't seem to find a hook for adding/updating user meta
add_user_meta( 'user_id', 'custom_key', 'custom_value');
when creating an order in woocommerce admin (woocommerce->orders->add order), backend.
Using
add_action('woocommerce_process_shop_order_meta', 'admin_process_shop_order', 10, 1);
This works fine for doing things while the order is processed. However, I need to get the customer ID, which from what I can tell doesn't exist until the order is actually created (makes sense).
So my question is, what hook (or other solution) can I use to get the customer ID once the order is created and searchable with
get_post_meta($order_id, '_customer_user', true);

Answer 1

Thank you #Gugan for your suggestions! It looks like that with your help I was finally able to get this mess sorted :)
Since I only wanted this to fire one time, i.e. when the order is created (and not again when updated), I hade to combine two actions.
First 'woocommerce_process_shop_order_meta'. Here I can check if the post meta exists (if it does, the order has already been created and should be left alone)
function check_order($post_id){
$new_order = get_post_meta($post_id, '_customer_user', true);
if(!$new_order){
add_action('woocommerce_order_status_[MY_CUSTOM_ORDER_STATUS]-processing', 'total_count');
}
}add_action('woocommerce_process_shop_order_meta', 'check_order', 10, 1);
If this is a new order move on to 'woocommerce_order_status_[MY_CUSTOM_ORDER_STATUS]-processing' (with my function 'total_count')
function total_count($post_id){
$order = wc_get_order($post_id);
$customer_id = $order->get_user_id();
$user_role = get_user_meta($customer_id, 'wp_capabilities', true);
$custom = serialize(array('[MY_CUSTOM_USER_ROLE]' => true));
$today = date('Y-m-d');
if($user_role = $custom){
$current_total = get_user_meta($customer_id, 'total', true);
$increment_total = $current_total+1;
update_user_meta( $customer_id, 'total', $increment_total);
update_user_meta( $customer_id, 'last', $today);
}
}
Now I only get an increment on my custom user metas "total" and "last" if this is a new order and if the customer is of my custom user role. Another plus to this is that it will only work for one order status (i.e. in my case [MY_CUSTOM_ORDER_STATUS]-processing).
Just jotting down my solution here for anyone else looking to handle similar custom order creation work.