Lots of Telemetry Warnings

[andyl]

When I compile or run Tableau, I get many Telemetry Warnings

I get the same behavior on Elixir 1.15 and 1.16

I believe the warnings come from a library schematic in the telemetry_wrap function of schematic.ex.

Here's my workaround to remove the telemetry warnings:

Does anyone else see these warnings?

Are the telemetry metrics in Schematic necessary?

Is there a way to suppress the telemetry warnings without altering the Schematic code?

[mhanberg]

It happens because schematic is being run at compile time, but the telemetry application hasn't started yet.

I haven't looked closely into how to fix it yet.

[andyl]

Gotcha. If you're up for it, I could submit PR to schematic to disable telemetry at compile time, and/or to allow application config to optionally disable schematic telemetry at run time. If you'd rather defer, no problem - lmk.

[mhanberg]

I think it makes more sense to figure out how to start the telemetry application before the modules compile, or (which i think i'll do anyway) rewrite the parts that use schematic at compile time to use it at runtime.

[andyl]

Sounds good. Just FYI here is the predicate code I used in my fork:

defmodule Schematic.TelemetryCfg do
  @moduledoc """
  Manage telemetry settings for Schematic.

  This module performs two functions:

  1. check to see if the current execution environment is `run-time` or
    `compile-time` (we want to disable telemetry at compile time).

  2. check to see if the application config has disabled telemetry

  ## Example

  In `config/config.exs`:

  ```elixir
    config :schematic, :config, disable_telemetry: true
  \```
  """

  @disable_telemetry_predicate Application.compile_env(:schematic, :config)[:disable_telemetry]

  @doc """
  Predicate used to determine if telemetry should be enabled in `Schematic`.

  To optionally disable schematic telemetry in your application, enter the following into your `config/config.exs` file:

  ```elixir
    config :schematic, :config, disable_telemetry: true
  \```
   """
  def enable_telemetry? do
    running?() && telemetry_allowed?()
  end

  defp telemetry_disabled? do
    @disable_telemetry_predicate
  end

  defp telemetry_allowed? do
    !telemetry_disabled?()
  end

  # from https://elixirforum.com/t/is-it-possible-to-detect-if-code-is-executing-at-compile-time/57728

  def compiling? do
    # TODO: When we depend on Elixir v1.11+ only, remove function_exported and elixir_compiler_pid
    process_alive?(:can_await_module_compilation?) ||
      process_alive?(:elixir_compiler_pid)
  end

  defp process_alive?(:can_await_module_compilation?) do
    Code.ensure_loaded?(Code) &&
      function_exported?(Code, :can_await_module_compilation?, 0) &&
      apply(Code, :can_await_module_compilation?, [])
  end

  defp process_alive?(name) do
    case Process.get(name) do
      nil -> false
      pid when is_pid(pid) -> true
    end
  end

  defp running? do
    ! compiling?()
  end
end

[mhanberg]

a partial fix i believe is released with 0.14.2

[mhanberg]

This should be completely fixed with 0.14.3