I’m doing some experimentation, and I ran into an issue with my Registry setup.
I have an event where I start some doomed tasks:
def handle_event("start_processes", _, socket) do
for _ <- 1..5 do
name = :rand.bytes(5) |> Base.url_encode64(padding: false)
task =
TaskSupervisor
|> Task.Supervisor.async_nolink(fn ->
Process.sleep(to_timeout(second: :rand.uniform(9)))
raise "Crash!"
end)
Registry.register(ProcessesRegistry, name, task.pid)
task
end
processes = Registry.select(ProcessesRegistry, registry_select_all())
{:noreply, assign(socket, processes: processes)}
end
I’d like to update my LiveView about the status of these tasks:
<div>
<p>Current process: {inspect(self())}</p>
<p>Registry process: {inspect(Process.whereis(ProcessesRegistry))}</p>
<.button phx-click="get_registered_processes">Refresh Processes</.button>
<.button phx-click="start_processes">Start Processes</.button>
<h2>Background Processes</h2>
<%= for pid <- @processes do %>
<div>PID: {inspect(pid)}</div>
<% end %>
</div>
def handle_info({:DOWN, _ref, :process, pid, _reason}, socket) do
IO.puts("handling DOWN message in #{inspect(socket.root_pid)}")
[{key, {_, _}}] = Registry.select(ProcessesRegistry, [{{:_, :_, pid}, [], [:"$_"]}])
Registry.unregister(ProcessesRegistry, key)
processes = Registry.select(ProcessesRegistry, registry_select_all())
{:noreply, assign(socket, processes: processes)}
end
But there is a very simple problem: what happens when the LiveView page is refreshed?
The PID of the LiveView is changed, which causes the :DOWN messages to be sent to the old LiveView process instead of the new one.
Is there a simple way to solve this problem?
Thanks 
