---
title: "Measure rate, errors and duration · Agent Wranglers"
url: https://agentwranglers.se/playbook/operations/metrics-and-traces/red-metrics
updated: 2026-10-20
licence: "All rights reserved"
---

# Measure rate, errors and duration

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Required
- Chapter: [Metrics and traces](https://agentwranglers.se/playbook/operations/metrics-and-traces)
- Rule: For every service, record the request rate, the error rate and the time each request takes, split by route.
- How: Use a metrics library or an agent, such as OpenTelemetry or a Prometheus client. Record duration as a histogram, so you can read percentiles such as p95 and p99. Averages hide the slow requests users notice. For a single small service, derive the three numbers from the access log, such as status codes and request times per line.
- Check: For each service, a query returns requests per second, errors per second and p95 duration for the last hour, per route. For a single service, a daily script over the access log may produce the same three numbers.

Example:

```text
# Prometheus queries
# OpenTelemetry metric http.server.request.duration, as exported to Prometheus
sum by (http_route) (rate(http_server_request_duration_seconds_count[5m]))
sum by (http_route) (rate(http_server_request_duration_seconds_count{http_response_status_code=~"5.."}[5m]))
histogram_quantile(0.95, sum by (le, http_route) (rate(http_server_request_duration_seconds_bucket[5m])))
```

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers operations playbook: https://agentwranglers.se/playbook/operations/metrics-and-traces/red-metrics`.

- Next: [Keep metric labels few and bounded](https://agentwranglers.se/playbook/operations/metrics-and-traces/bounded-metric-labels)
- [Metrics and traces](https://agentwranglers.se/playbook/operations/metrics-and-traces)