[lesnik512]

Summary

FastStream can run telemetry cleanup after concurrent dispatch returns, before the background task starts or finishes. This can leave the Kafka consumer process span unexported or end it too early.

During FastStream application startup, initialize_concurrent_processing() automatically adapts existing FastStream KafkaTelemetryMiddleware registrations that follow KafkaConcurrentProcessingMiddleware. The adapter preserves middleware order and telemetry settings, and ends the process span after both consume execution and middleware cleanup finish.

Downstream services using this setup only need to upgrade faststream-concurrent-aiokafka. They keep their existing middleware registrations and OpenTelemetry dependencies. The base package still works without OpenTelemetry.

Validation

• Live Kafka telemetry tests passed on unpatched FastStream 0.7.1 and 0.7.8, covering successful processing, handler failure, cancellation, inline processing, router registration, and repeated initialization.
• A clean base installation initialized successfully without OpenTelemetry.
• Full suite passed with 262 tests and 100% coverage. Ruff and ty checks passed.