Metrics

The library emits OpenTelemetry-compatible metrics via System.Diagnostics.Metrics. When no listener is attached, metrics are zero-cost no-ops.

Table of contents

1. Available Metrics
   1. Tag Values
2. Subscribing to Metrics
3. Compatible Listeners
   1. Local Debugging with dotnet-counters

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Available Metrics

Instrument	Type	Tags	Description
kafkaworker.messages.processed	Counter	topic, status	Messages processed by the main consumer
kafkaworker.messages.processing_duration	Histogram (ms)	topic	Processing duration per message
kafkaworker.messages.dlq_published	Counter	topic, dlq_topic	Messages published to the dead letter queue
kafkaworker.dlq.messages_reprocessed	Counter	topic, dlq_topic	Messages reprocessed from the DLQ back to the original topic
kafkaworker.dlq.messages_skipped	Counter	topic, reason	Messages skipped during DLQ reprocessing

Tag Values

status (on messages.processed):

• success — Message processed successfully
• invalid — Message rejected via InvalidMessageException
• failed — Message failed after all retries

reason (on dlq.messages_skipped):

• invalid — Message marked as invalid (will never succeed)
• max_attempts — Message exceeded the maximum reprocess attempts
• missing_topic — Original topic header is missing from the DLQ message

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Subscribing to Metrics

Add the KafkaWorker meter to your OpenTelemetry configuration:

builder.Services.AddOpenTelemetry()
    .WithMetrics(metrics =>
    {
        metrics.AddMeter("KafkaWorker");
        metrics.AddPrometheusExporter(); // or any exporter
    });

The meter name is "KafkaWorker" — this is the only name you need to subscribe to.

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Compatible Listeners

Metrics work with any System.Diagnostics.Metrics-compatible listener:

• OpenTelemetry — Export to Prometheus, Jaeger, OTLP, etc.
• Azure Monitor — Via the Azure Monitor OpenTelemetry exporter
• dotnet-counters — CLI tool for local debugging
• Prometheus — Direct export via AddPrometheusExporter()

Local Debugging with dotnet-counters

dotnet counters monitor --process-id <PID> --counters KafkaWorker

This shows real-time metric values without any exporter configuration.