Monitoring

Aeron exposes a rich set of lock-free counters in shared memory. Knowing which ones matter — and what a bad value looks like — is the difference between catching a problem at 2pm and getting paged at 2am.

In this section

• Monitoring Aeron®: Metrics and Alerting for Your Observability Platform — How to get Aeron and Aeron Cluster telemetry out of the CnC file and into Prometheus/Grafana/Datadog, the counters that matter mapped to failure modes, and the alert conditions to wire up — OSS DIY exporter vs Premium Aeron Insights.
• Hot-Path Logging & Metrics Capture — How to log events, record per-stage latencies, and expose your own metrics from the matching thread without adding jitter — async logging off the hot path, in-process HdrHistogram, and publishing your own counters into Aeron®'s shared-memory counter infrastructure.

The counters that page you

Signal	What it means	Look for
Back-pressure	Publisher is being throttled by an unready subscriber	Sustained non-zero → consumer can’t keep up
NAKs / retransmits	Packet loss on the wire	Rising rate → network or buffer sizing problem
Loss gaps	Receiver waiting on missing data	Non-trivial gaps → loss + slow recovery
Conductor duty cycle	Driver event loop latency	Spikes → CPU contention / lost core isolation

Monitor before you tune

Counters are also your tuning feedback loop. Change one knob, watch the relevant counter, keep the change only if the signal improves. See Performance Tuning.

Note

For the meaning of each counter at the protocol level, The Aeron Files has a dedicated counters section. Here we focus on which to watch in production and why.