mastodon user federation request prioritisation

server.nginx

map $request_uri $ap_resource_user {
  ~^/@(\w+)$                    $1;
  ~^/@(\w+)/\d+$                $1;
  ~^/users/(\w+)$               $1;
  ~^/users/(\w+)/\w+$           $1;
  ~^/users/(\w+)/statuses/\d+$  $1;

  default         "";
}

lua_shared_dict your_dict_name 10m;

server {
  # ...
  
  set_by_lua_file $lua_prioritized /etc/nginx/lua/user_link_resolve_prio.lua your_dict_name;

  # ...
}

user_link_resolve_prio.lua

local ap_likely_user_url = ngx.var.ap_likely_user_url
local traffic_class = ngx.var.traffic_class
local ap_resource_id = ngx.var.ap_resource_id
local ap_resource_user = ngx.var.ap_resource_user

if (not (traffic_class == "AP_G" or traffic_class == "AP_F"))
    or ap_resource_user == "" or ap_resource_user == nil then
    return nil
end

local shared_dict = ngx.shared[ngx.arg[1]]

local shared_val, _ = shared_dict:get(ap_resource_user)

if shared_val then
    ngx.var.traffic_class = "AP_G"
    return 1
end

if ap_likely_user_url == "1" then
    shared_dict:set(ap_resource_user, true, 10)
    ngx.var.traffic_class = "AP_G"
    return 1
end

return 0