Highly available gen server

[molten cradle]

Hi,

Let's say I have application node A, B and C and I have a global registered gen server registered, so it's only spawned on node C. When node C dies, I want it to be started on either note A or B.

Is this possible? It seems like it's not happening by default.

Additional information
I'm writing a chat module for my application where I spawn a gen server for each chat session (only holding 10 chat messages per process).

I've used a dynamic supervisor so I can spawn them alá carte and I'm using a global registry so only one gen_server for the chat session can be spawned.

This worked great until I tried to add and remove nodes from my elixir cluster.

[molten cradle]

I guess I could implement my own thing using a monitor

[native elm]

Sounds like you want something like Horde: https://github.com/derekkraan/horde

For a more audio-visual demonstration of Horde: https://www.youtube.com/watch?v=nLApFANtkHs

[undone kestrel]

Here's a walkthrough of the monitor based solution: https://moosecode.nl/blog/highlander_there_can_be_only_one

[native elm]

Such a good name.

[molten cradle]

Ah yes, Horde is something I've had my eyes on. I thought there would be something in OTP that handles it for me though 🙂

[undone kestrel]

For what it's worth, you're probably better off using something like persistent hashing + a hashring to spread processes across your cluster rather than having every node monitor each one. Especially since it sounds like you will have many