How to check globally named Agent?

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5

As was already pointed out, the BEAM won’t let you start a second process with the same name. Since in your code you’re not handling the return:

you could just have Agent.start_link(fn -> %{} end, [name: {:global, user_id}]) and get the same result. Assuming that’s just example code and you do care about the response, you can do something like:

def ensure_agent(user_id) do
  case Agent.start_link(fn -> %{} end, [name: {:global, user_id}]) do
    {:ok, pid} -> {:ok, pid}
    {:error, {:already_started, pid}} -> {:ok, pid}
    response -> response
  end
end

Your code can then call ensure_agent/1and will know that if {:ok, pid} is returned an agent is ready.

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