Convenience wrapper library around Erlang's global module to ensure
a single instance of a process is kept running on a cluster of nodes.
The package can be installed as:
- Add
singletonto your list of dependencies inmix.exs:
```elixir
def deps do
[{:singleton, "~> 1.0.0"}]
end
```
- Ensure
singletonis started before your application:
```elixir
def application do
[applications: [:singleton]]
end
```
Use Singleton.start_child/3 to start a unique GenServer process.
Singleton.start_child(MyServer, [1], {:myserver, 1})
Execute this command on all nodes. The MyServer GenServer is now
globally registered under the name {:global, {:myserver, 1}}.
As soon as you connect nodes together, you'll see logger messages like:
04:56:29.003 [info] global: Name conflict terminating {MyServer, #PID<12501.68.0>}
When you now stop (or disconnect) the node on which the singleton process runs, you'll see it get started on one of the other nodes.
In case you run more than 3 singleton you'll need to increase the
max_restarts of DynamicSupervisor.
config :singleton,
dynamic_supervisor: [max_restarts: 100]