Hooking Up Fly Metrics

Summary

Fly apps include built-in Prometheus instrumentation, exposing automatically collected metrics through a public Prometheus endpoint and allowing applications to export custom metrics. The walkthrough connects an organization’s Fly Prometheus URL to Grafana with a Fly token, then explains dashboard variables and PromQL queries using counters, gauges, histograms, labels, irate(), rate(), increase(), sum(), and regional grouping. Examples cover network traffic, TCP connections, HTTP response rates by region, and response-time heatmaps built from histogram buckets ranging from 5ms to 120s. Application instrumentation is shown for Go, Python Flask, and Node.js, with scraping configured in fly.toml through a metrics port and path. The post concludes that metrics are currently free, with some tier free forever, although a future pricing plan is expected for ambitious usage.

Takeaways

1. 1

   Fly’s Prometheus endpoint is organization-specific; Grafana authentication is configured with a custom Authorization header containing a Fly token.

2. 2

   The examples use counters for network and HTTP events, increase() for connection charts, regional aggregation for request rates, and histogram buckets for response-time heatmaps.

3. 3

   Applications can expose custom Prometheus metrics through a /metrics endpoint, with Fly scraping the configured port and path; metrics are currently free, though future pricing is planned for ambitious usage.