Monitoring
Nagios checks, plugins, alerting and reducing alert fatigue.
Monitoring articles
Alertmanager Routing and Silences
Alertmanager takes firing alerts from Prometheus and decides who gets paged, grouped how, and when. Here's the routing tree, grouping, inhibition, and silences.
October 24, 2026A node_exporter Metrics Guide
node_exporter emits hundreds of host metrics. Here are the two dozen that matter, the PromQL to graph them, and sensible alert thresholds.
October 24, 2026Loki for Logs
Loki is 'Prometheus for logs' — it indexes labels, not full text, so it's cheap. Here's LogQL, the cardinality rule, and how it differs from Elasticsearch.
October 24, 2026SLO Burn-Rate Alerts
Alerting on 'error rate > 1%' is noisy. Alerting on 'we'll burn the whole month's error budget in a day' is actionable. Here's the burn-rate method and the queries.
October 24, 2026The Prometheus Blackbox Exporter
The blackbox exporter probes your services the way a user would — is it up, is TLS valid, is DNS resolving. Here's the module config and the relabeling that makes one exporter probe many targets.
October 24, 2026PromQL for Beginners
PromQL trips people up because counters must be wrapped in rate() and you can't average a percentile. Here's the mental model and the queries you'll actually write.
October 24, 2026Monitoring What Actually Matters
You can't monitor everything, and you shouldn't try. The golden signals, RED/USE, and SLOs give you a short list that catches real problems.
October 24, 2026Alert Fatigue and How to Fix It
When every alert is ignorable, the one that matters gets ignored too. A practical process for cutting alert volume by 80% without losing coverage.
October 24, 2026Nagios Active vs Passive Checks, and When to Use Each
The difference between Nagios polling a service and a service reporting in — and the freshness-check setting that keeps passive checks honest.
October 24, 2026Prometheus Cardinality Management
Every unique label combination is a time series, and Prometheus holds them all in memory. A label with a request ID in it can OOM your Prometheus — here's how to find and fix it.
August 31, 2026Writing a Custom Nagios Plugin
A Nagios plugin is any executable that follows four exit codes and a one-line output convention. Here's the contract and two complete, correct examples.
August 28, 2026Nagios Notifications and Escalations
Nagios notification logic has a lot of moving parts — states, intervals, time periods, escalations, dependencies. Here's how they combine to page the right person once.
August 28, 2026