Alloy 404s OTLP metrics, so each service gets a MeterProvider with a
PrometheusMetricReader (same Resource as traces) served by
prometheus_client on its own port instead of a FastAPI route: gateway's
port 8000 is publicly routed by Traefik, and the audit worker has no HTTP
app. Host/port come from OTEL_EXPORTER_PROMETHEUS_HOST/PORT. Setting the
provider before the instrumentors also turns on their built-in HTTP and
DB pool metrics.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Movses AslanyanandClaude Opus 5.5
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