I’m trying with ETS tables. There’s something I don’t get.. I create the table in the Command module, as soon as it’s loaded:
@on_load :init
def init() do
res = :ets.new(:commands, [
:named_table,
:ordered_set,
:public,
{:read_concurrency, true},
{:write_concurrency, true}
])
whereis = :ets.whereis(:commands)
content = :ets.tab2list(:commands)
Logger.debug("table created: #{inspect(res)} #{inspect(whereis)} #{inspect(content)}")
end
This works fine:
21:45:58.988 [debug] table created: :commands #Reference<0.2865878229.9043973.175739> []
The __using__ macro is like this now, with a Process.sleep to make sure the ETS table is setup at that point:
defmacro __using__(opts) do
quote do
@behaviour Command
@on_load :register_command
def register_command() do
Process.sleep(5000)
Command.register_command(__MODULE__, unquote(opts))
end
def parse_args(_cmd_args), do: {:ok, nil}
defoverridable [parse_args: 1]
end
end
And then in the register_command, I try to insert:
def register_command(module, cmd_opts) do
Logger.debug("register_command: #{module} #{inspect(cmd_opts)}")
cmd_name = Keyword.fetch!(cmd_opts, :name)
:ets.insert(:commands, {cmd_name, module})
end
But this, after the 5 seconds, crashes:
21:53:54.865 [warn] The on_load function for module Elixir.Commands.Info returned:
{:badarg,
[
{:ets, :insert, [:commands, {"info", Commands.Info}],
[error_info: %{cause: :id, module: :erl_stdlib_errors}]},
{Command, :register_command, 2, [file: 'lib/command.ex', line: 60]},
{:code_server, :"-handle_on_load/5-fun-0-", 1,
[file: 'code_server.erl', ...]}
]}
21:53:54.858 [error] Process #PID<0.211.0> raised an exception
** (ArgumentError) errors were found at the given arguments:
* 1st argument: the table identifier does not refer to an existing ETS table
(stdlib 3.15.2) :ets.insert(:commands, {"info", Commands.Info})
lib/command.ex:60: Command.register_command/2
(kernel 8.0.2) code_server.erl:1317: anonymous fn/1 in :code_server.handle_on_load/5
How does the table name, :commands, not refer to an existing ETS table? I don’t get. Is this because it’s happening at compile time and when the compilation finishes, the ETS table dies?