gus
Calling a GenServer on a remote machine
Hey all, happy 2024!
I think I have on my hands a configuration and OTP problem - I’m pretty sure I have all the pieces, just not sure how to put it together.
I have a Nerves device which is connected to a sensor. I have created a GenServer to read the sensor periodically, save the data and provide it upon a caller’s request. This device also a has a LiveView UI which graphs the value of the sensor over time. This all works great on the device.
Where it breaks down is in development - I want to be able to develop the UI on my local machine, but use live data by calling the GenServer running on the device. I have enabled epmd and can connect to the remote node through iex, but now I’m trying to figure out how to ‘re-route’ all of the calls to the sensor GenServer to the Nerves device when running the application on the host.
I am considering two approaches to this problem. First, GenServer will accept any name registration as outlined in the docs, including processes on remote nodes. I think I could look up the remote PID on application start, and store that in application config for use later. As a second approach, I think there should be a way to use Registry or :global to lookup the correct process to direct the requests to.
Are there any recommendations on how to best do this?
Thanks!
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hubertlepicki
No, and it’d be interesting to see what works and what doesn’t work.
I am mentioning it because I saw the erlang/elixir code explicitly handling endiness in some blog posts about handling data from smart sensors, and I suspect that the distribution protocol will handle it just fine but the payloads you send between nodes may require conversion. For example: Smart Sensors with Erlang and AtomVM: Smart cities, smart houses and manufacturing monitoring - Erlang Solutions
mudasobwa
Well, there are a lot of good libraries above, but as I see the problem statement, one does not need any external library, nor even pg here.
Just name a process as {:global, Name}, and make sure the nodes are connected (by calling Node.connect/1 and checking it with Node.list/0.
Then :global.whereis_name/1 will give you a remote PID back, and you might use all the functions from GenServer using {:global, Name} as a remote process name.
D4no0
Well that is another question.
I am not entirely sure, but my thinking is that inter-node communication is using functionality from term_to_binary, there seems to be a more comprehensive documentation here: Erlang -- External Term Format
schneebyte
Erlang -- pg is simple, flexible and already included in Erlang.
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