Am totally new to Libcluster but I want to start two phoenix app instances on my local machine in dev mode. So this is what I have done so far based on the libcluster documentation.

This is my application.ex.

def start(_type, _args) do
  topologies = Application.get_env(:libcluster, :topologies) || []
  children = [
   # start libcluster
   {Cluster.Supervisor, [topologies, [name: MyApp.ClusterSupervisor]]},
   # ..other children..

And my config/dev.exs

config :libcluster,
topologies: [
  example: [
    # The selected clustering strategy. Required.
    strategy: Cluster.Strategy.Epmd,
    # Configuration for the provided strategy. Optional.
    config: [hosts: [:"a@127.0.0.1", :"b@127.0.0.1"]],
    # The function to use for connecting nodes. The node
    # name will be appended to the argument list. Optional
    connect: {:net_kernel, :connect_node, []},
    # The function to use for disconnecting nodes. The node
    # name will be appended to the argument list. Optional
    disconnect: {:erlang, :disconnect_node, []},
    # The function to use for listing nodes.
    # This function must return a list of node names. Optional
    list_nodes: {:erlang, :nodes, [:connected]},
  ]
]

My first question is what is the example key above? can it be renamed to anything? Should it be the application name?. Secondly, how would I start this in my shell. I tried

PORT=4000 elixir --name a@127.0.0.1 -S mix phx.server  & PORT=4001 elixir --name 
b@127.0.0.1 -S mix phx.server

It just got a warning message unable to connect to :"b@127.0.0.1" and the normal phoenix app was started. I have no idea how to do this properly. Any ideas or guidance are welcome.