For deployments that have https://hg.prosody.im/trunk/file/tip/plugins/muc/register.lib.lua#l7 and use https://modules.prosody.im/mod_muc_http_auth.html users can still register to a MUC even if they are not allowed to join. That means they would receive RAI or RMN, for instance.

module:set_global();

local log = _G.log;

module:add_timer(60-os.date("%S"), function (now)
	log("info", "-- MARK --");
	return 90 - ((now + 30) % 60);
end);