Document metrics alerting, retention, cost, and limits#2413
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The metrics page covered querying and dashboards but never said how to set up alerting, how long metrics are retained, whether the managed Prometheus and Grafana cost anything, or what limits apply. - Add an Alerting section: Fly has no built-in alerting, so set it up against the Prometheus endpoint with Grafana alerting or Prometheus + Alertmanager, or deploy the Observability for User Apps blueprint. - Add a Retention, cost, and limits section: ~15-day retention (with a pointer to run your own stack for longer), no current additional charge (subject to change), and the 16 KiB metrics-endpoint response cap plus high-cardinality drop behavior.
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kcmartin
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Jun 17, 2026
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Thank you! I left a few small suggested copy changes and naming updates.
Co-authored-by: Kristin Martin <kcmartin@users.noreply.github.com>
Co-authored-by: Kristin Martin <kcmartin@users.noreply.github.com>
Co-authored-by: Kristin Martin <kcmartin@users.noreply.github.com>
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The metrics page covered querying and dashboards but never said how to set up alerting, how long metrics are retained, whether the managed Prometheus and Grafana cost anything, or what limits apply.
Add an Alerting section: Fly has no built-in alerting, so set it up against the Prometheus endpoint with Grafana alerting or Prometheus + Alertmanager, or deploy the Observability for User Apps blueprint.
Add a Retention, cost, and limits section: ~15-day retention (with a pointer to run your own stack for longer), no current additional charge (subject to change), and the 16 KiB metrics-endpoint response cap plus high-cardinality drop behavior.