The SDK's OTP application. Declared as mod: in mix.exs, so it starts
automatically the moment :metrixwire is a dependency of the host app.
On boot it:
- resolves
MetrixWire.Config(app env + ENV fallbacks), - starts
:inetsand the:metrixwirehttpc profile (transport HTTP client), - starts a
Task.Supervisor(fire-and-forget batch sends) and theMetrixWire.TransportGenServer (batching + flushing), - attaches every
:telemetryhandler.
Result: adding the dep + setting METRIXWIRE_KEY makes Phoenix fully automatic —
zero code changes. With no API key the SDK boots in disabled mode (a warning is
logged) and attaches nothing, so it's inert.