GenServer and Global Registration

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Quick question about a global process and restarts…

I have a genserver which is registered using {global, term} and I’ve been doing some testing using a 3 node cluster.

I can (from the terminal) kill the pid using whereis(); and I see the process get restarted; usually on the same node it was running on.

If I kill the VM on the node the process is running on (using control-C), the other two nodes (the supervisors), the process does not get restarted. genserver:whereis returns nil at this point.

The process is a worker managed by a supervisor; (there are a few other workers) and the restart strategy is one_to_one.

So I’m trying to figure out how/where to tell something that I want the remaining nodes to restart the process. Perhaps I need to monitor the pid and messages myself? Do I need to design a leader/election thing or is there an idiomatic / supervisor way of doing this?

Link to the GenServer code:

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You specify how/when/if an Application should replicate to another node based on the information at it’s setup. The official documentation (erlang) is at: http://erlang.org/doc/design_principles/distributed_applications.html

Basically you need to say what nodes it is allowed to run at and with what priorities at startup, and there are a ton more options too. :slight_smile:

For a specific GenServer, if you only want one instance of it running (when the application is running in multiple places), then something like gen_leader is what you want. :slight_smile:

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Zookeeper and other fancy consensus tools are useful if you need to be absolutely sure only one instance runs, even in the case of netsplits. If you can live with a weaker guarantee, then it’s very simple to setup the GenServer for automatic fallover:

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