benzene-otel

OpenTelemetry integration for Benzene Python. The port already traces itself — benzene.mesh.trace_middleware emits one TraceEvent per invocation — but that tracing was Benzene-internal only, feeding a mesh collector rather than a general OTel pipeline. This package exports it to a real OpenTelemetry SDK, and adds a response-as-event pattern mirroring .NET's Benzene.ResponseEvents. Depends on benzene-core and benzene-mesh.

pip install "benzene-otel[otel]"   # the [otel] extra pulls opentelemetry-api / opentelemetry-sdk

OtelTraceExporter is a benzene.mesh.TraceExporter, so it wires into the existing tracing middleware — no second instrumentation. Each finished span maps one-to-one onto an OTel span: topic → span name, started_at/duration_ms → OTel start/end nanoseconds, every field → a benzene.* attribute, and the semantic status → the OTel span status.

from benzene.mesh import trace_middleware
from benzene.otel import OtelTraceExporter, RecordingSink, response_event_interception

# Trace export: forward the port's own spans to OpenTelemetry (real tracer acquired lazily).
definition.middleware.insert(0, trace_middleware(OtelTraceExporter(), service="orders"))

# Response-as-event: publish each result to a sink after the handler runs.
sink = RecordingSink()  # swap for an OTel-log / outbox / audit-topic sink in production
definition.middleware.append(response_event_interception(sink))

• OtelTraceExporter — consumes the mesh trace model and pushes each TraceEvent to an injected (or lazily created) OTel tracer. The tracer is a duck-typed seam (OtelTracer / OtelSpan), so a fake tracer exercises it with no opentelemetry installed; export is non-blocking and never raises, so a bad tracer can't break the invocation it observes.
• response_event_interception(sink, *, when=..., include_payload=...) — after await next(), emits a ResponseEvent (topic, status, correlation id, optional payload) to a ResponseEventSink. Emits every result by default; pass when=lambda r: r.is_successful for successes only. A sink that raises is logged and swallowed — emitting an event never breaks the pipeline.
• RecordingSink — an in-memory list of emitted events, the fake for tests and dogfooding.

Nothing here needs a collector, a real clock, or the OpenTelemetry package to run in tests: the tracer and sink are injectable seams, so the whole surface is exercised in memory. Mirrors the role of .NET's Benzene.Diagnostics OTel wiring and Benzene.ResponseEvents, and contributes the benzene.otel subpackage to the shared benzene namespace.