Tracing middleware powered by the instrument library.

Opens one server span per request, attaches OpenTelemetry HTTP server semantic attributes (method, status, route, scheme, protocol, peer), and propagates W3C traceparent/tracestate context extracted from the inbound headers.

State: #{tracer => binary() | atom()} (defaults to <<"livery">>).

The span is kind => server and gets these attributes:

• http.request.method
• url.path
• url.scheme
• network.protocol.name (http/1.1 / http/2 / http/3)
• server.address
• client.address
• user_agent.original
• http.response.status_code (set after the handler returns)

Errors from the handler are recorded on the span via instrument_tracer:record_exception/2 and re-raised so the request process's own crash handling still runs.

Correlating logs with traces

Call install_logger/0 once at boot to add the instrument logger filter. It enriches every logger event emitted while a span is active (so, inside this middleware) with trace_id, span_id, and trace_flags in the event metadata. Stack this middleware outside livery_access_log and the access-log lines carry the same ids as the request's span.