[Question] No env and prod converges to the same value. Invitation to human error?

[linearregression]

When people (or mistake in the script) forget to put value for env, it will output the same
value as if "prod" has been put in. It looks like it hides a mistake, and makes is a hard to find error.

Suggest to make env a required settings, not optional, during init for least surprises.

File: elixometer/lib/elixometer.ex

def name_to_exometer(metric_type, name) when is_bitstring(name) do
    config = Application.get_all_env(:elixometer)
    prefix = config[:metric_prefix] || "elixometer"
    base_name = case config[:env] do
                  nil -> "#{prefix}.#{metric_type}.#{name}"    <<<<<<<<<<<<<<<<<<<<<<<
                  :prod -> "#{prefix}.#{metric_type}.#{name}"   <<<<<<<<<<<<<<<<<<<<<<
                  env -> "#{prefix}.#{env}.#{metric_type}.#{name}"
                end

[scohen]

I think it would be bad if your application failed to boot because your metrics package wasn't configured correctly; especially if you left out the env.
This default is reasonable; it leave out an environment, and the worst possible outcome is you taint a metric with non-prod data.

[linearregression]

It can go both ways. It is about what do you mean by a good state.
If it fails to boot, it will be right from the start of the whole app, not in the middle of it.
Whoever deployed it will be forced to fix it.

Right now the process owns the ets. So risk is small.
Same argument goes with if you want a default, why no a :dev or :test env. Why :prod which is more important to make sure the state is as valid and clean as you can get

[scohen]

I think prod is more valid because that's the env where I really don't want stuff to fail.

Imagine this: deploy goes out, servers don't boot and I'm running at reduced capacity until I can roll back. Not a great scenario.

[linearregression]

Then at least log a warning or something, a default is being used.
It sounds like you are referring deploy it all at once but not issue if it is under canary deployment.

[zorbash]

I think it makes sense at least to log a warning when config[:env] is missing.
Other alternatives would be to try to guess the env from Mix.env or use something harmless like "default_env".