# Dynamic nodes using global registry **URL:** \ **Category:** Questions / Help\ **Tags:** distributed-erlang, dynamic-nodes\ **Created:** [January 14, 2024, 7:48am UTC](https://erlangforums.com/t/dynamic-nodes-using-global-registry/3190 "2024-01-14T07:48:11Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![msheldon](https://erlangforums.com/letter_avatar_proxy/v4/letter/m/58f4c7/32.png) [@msheldon](https://erlangforums.com/u/msheldon)\ **Post date:** [January 14, 2024, 7:48am UTC](https://erlangforums.com/t/dynamic-nodes-using-global-registry/3190/1 "2024-01-14T07:48:11Z")
I apologize if this is a known issue — my searching has not turned up anything. I have a `gen_server` that globally registers itself, but I cannot seem to use it from a dynamic node. Non-dynamic nodes work: If I `erl -name something`, then `net_adm:ping('server_node')`, I can then use client functions (that do things like `gen_server:call({global, ?SERVER}, ...)` All good. But, if I `erl -name undefined`, then `net_kernel:connect_node('server_node')` that succeeds as do pings, but `nodes()` is empty and attempts to use client functions fail with ‘noproc’. `global:whereis_name('global_service_name')` produces `undefined`. If I register a process _locally_ on the server node, I can send messages to it using `gen_server:call({'registered_name', 'server_node'}, ...)`. Conclusion: dynamic nodes don’t seem to sync with the global registry. (I tried `global:sync()` without any change: `nodes()` is still `[]` and the service cannot be found.) I am running Erlang/OTP 25 on a Chromebook and version 26 on a MacBook Pro. Same behavior. Am I missing something? Is there a way to get dynamic nodes to participate in the global registry? Or do I have to plumb the registered name and node name through everything? Help is appreciated! ---
**Author:** ![mmin](https://erlangforums.com/user_avatar/erlangforums.com/mmin/32/2193_2.png) [@mmin](https://erlangforums.com/u/mmin)\ **Post date:** [January 14, 2024, 12:52pm UTC](https://erlangforums.com/t/dynamic-nodes-using-global-registry/3190/2 "2024-01-14T12:52:52Z")
Dynamic node is also a hidden node, so global doesn’t keep track of them. I don’t know if one can override that. One workaround would be to execute that gen\_server call on the node you’re connecting to, e.g. via `erpc`. ---
**Author:** ![rvirding](https://erlangforums.com/user_avatar/erlangforums.com/rvirding/32/178_2.png) [@rvirding](https://erlangforums.com/u/rvirding)\ **Post date:** [January 14, 2024, 3:19pm UTC](https://erlangforums.com/t/dynamic-nodes-using-global-registry/3190/3 "2024-01-14T15:19:24Z")
I am just guessing here but isn’t the problem that you have given the node the name `undefined` which is the same as if it was undefined. What do you get when you call `node()` in that node? Also try `nodes(hidden)` and `nodes(connected)` and `nodes(known)`? ---
**Author:** ![msheldon](https://erlangforums.com/letter_avatar_proxy/v4/letter/m/58f4c7/32.png) [@msheldon](https://erlangforums.com/u/msheldon)\ **Post date:** [January 14, 2024, 6:24pm UTC](https://erlangforums.com/t/dynamic-nodes-using-global-registry/3190/4 "2024-01-14T18:24:04Z")
Thank you! I forgot hidden nodes exist! Dynamic nodes (nodes started with the name `undefined`) when they connect, do so as hidden nodes, which makes sense: ```erlang (3MEFLP0EW3HOO@192.168.1.98)23> nodes(hidden). ['do@192.168.1.98'] (3MEFLP0EW3HOO@192.168.1.98)24> nodes(known). ['do@192.168.1.98','3MEFLP0EW3HOO@192.168.1.98'] (3MEFLP0EW3HOO@192.168.1.98)25> nodes(). [] (3MEFLP0EW3HOO@192.168.1.98)26> ``` And the documentation does say that hidden nodes don’t participate in the global registry, which also makes sense. Am I right that there is no way for a non-participating node to query the global registry so `gen\_server:call({global, service}, Message) works? If I’m right, I can think of two obvious solutions: 1. Don’t use the global registry. Register the server process locally on the server node, and have the client functions specify `{server_name, server_node}' in the `gen\_server:call`and`gen\_server:cast` calls. 2. Leave the server globally registered, but have dynamic clients run the operation on the server node using `rpc:call`. This is gross, but for this particular case, it’s a kind of low-volume, administrative node I’m popping up. In a related application, I expect nearly all interactions to arise from dynamic nodes, and I would stick with option 1. If I’m missing something, please let me know, and thank you for the help! ---
**Author:** ![msheldon](https://erlangforums.com/letter_avatar_proxy/v4/letter/m/58f4c7/32.png) [@msheldon](https://erlangforums.com/u/msheldon)\ **Post date:** [January 14, 2024, 6:30pm UTC](https://erlangforums.com/t/dynamic-nodes-using-global-registry/3190/5 "2024-01-14T18:30:44Z")
@mmin Indeed — I hadn’t realized dynamic nodes were hidden, but of course they are! I saw Robert’s answer first, because it was most recent in my email inbox, but you both got it. Thank you!