[SR-Users] Notify registered users of primary server status change

Hi, I'm using kamailio as an intermediate proxy with survivability. That means I'm monitoring the primary server using the dispatch module, and if it goes down, I take control of all further requests. The main server acts as registrar, but I keep a copy a of the registered users list. There's a feature of Siemens (now Unify) phones and SBC where in this same scenario, the SBC will send a NOTIFY packet informing the status change to the phones. The phones then display a message indicating "limited service" and re-register. To indicate that they support this feature, phones send a "Supported: X-Siemens-Proxy-State" header when registering. The NOTIFY packet from the SBC includes the header "Event: server-mode-backup" or "Event: server-mode-normal" according to the main server status. I would like to replicate this functionality in kamailio. I looked at the presence module, as it already sends NOTIFY requests, but UACs have to subscribe to events first, and Siemens phones do not. I am trying to do it manually in the event_route[dispatcher:dst-down/up] triggers, but I can't find a way to iterate through all registered users. I would appreciate some assistance: - Is there some module I'm missing that implements something similar? - If not, how to iterate through all registered users to manually send a request to each of them? - If I send the requests using uac_req_send, will they be sent sequentially from the same thread? Thanks Neven Boric