opentelemetry_experimental: `otel_metric_reader` crashes when `export_interval_ms` config isn't specified

[cheerfulstoic]

The server crashes when trying to call collect_ because export_interval_ms/tref are undefined. Probably export_interval_ms should have a default or be validated earlier.

[cheerfulstoic]

Also, I noticed that things seem to go wrong when if unit and description aren't strings (for :otel_meter.create_counter, for example)

[tsloughter]

Thanks!

What is trying to call collect_? Do you just mean you did an Erlang trace or got a stacktrace that showed collect_ was being called when it crashed?

The export should be able to be undefined because that is what is used for polling vs pushing of metrics from the reader.

[cheerfulstoic]

Oh, sorry, I was debugging a lot of things 😅 I don't think it was a crash, I think it was simply that the metrics silently weren't sending when export_interval_ms wasn't set.

Here is an example config. If I set export_interval_ms then the metrics send, if I don't then the metrics don't send.

config :opentelemetry_experimental,
  readers: [
    %{
      module: :otel_metric_reader,
      config: %{
        # export_interval_ms: 1_000,
        exporter: {
          :otel_exporter_metrics_otlp,
          %{endpoints: ["http://0.0.0.0:4318"], protocol: :http_protobuf, ssl_options: nil}
        }
      }
    }
  ]