Alert rules

An alert rule is a set of evaluation criteria for when an alert rule should fire. An alert rule consists of:

Queries and expressions that select the data set to evaluate.
A condition (the threshold) that the query must meet or exceed to trigger the alert instance.
An interval that specifies the frequency of alert rule evaluation and a duration indicating how long the condition must be met to trigger the alert instance.
Other customizable options, for example, setting what should happen in the absence of data, notification messages, and more.

Grafana supports two different alert rule types: Grafana-managed alert rules and data source-managed alert rules.

Grafana-managed alert rules

Grafana-managed alert rules are the most flexible alert rule type. They allow you to create alert rules that can act on data from any of the supported data sources, and use multiple data sources in a single alert rule.

How Grafana-managed alerting works by default

Alert rules are created within Grafana and query one or more data sources.
Alert rules are evaluated by the Alert Rule Evaluation Engine from within Grafana.
Firing and resolved alert instances are forwarded to handle their notifications.

Supported data sources

Grafana-managed alert rules can query backend data sources if Grafana Alerting is enabled by specifying {"backend": true, "alerting": true} in the plugin.json file.

Find the public data sources supporting Alerting in the Grafana Plugins directory.

Data source-managed alert rules

Data source-managed alert rules can only query Prometheus-based data sources, such as Prometheus, Grafana Mimir, or Grafana Loki.

Alert rules are stored within the data source. In this distributed architecture, the separation of components can provide high-availability and fault tolerance, enabling the scaling of your alerting setup.

Alert rules are created and stored within the data source itself.
Alert rules can only query Prometheus-based data.
Alert rules are evaluated by the Alert Rule Evaluation Engine.
Firing and resolved alert instances are forwarded to handle their notifications.

Comparison between alert rule types

We recommend using Grafana-managed alert rules whenever possible, and opting for data source-managed alert rules when you need to scale your alerting setup.

The table below compares Grafana-managed and data source-managed alert rules.

Feature	Grafana-managed alert rule	Data source-managed alert rule
Create alert rules that query data sources supporting Alerting	Yes	No. Only query Prometheus-based data sources.
Mix and match data sources	Yes	No
Add expressions to transform your data and set alert conditions	Yes	No
Use images in alert notifications	Yes	No
Support for recording rules	Yes	Yes
Organization	Organize and manage access with folders	Use namespaces
Alert rule evaluation and delivery	Alert evaluation is done in Grafana, while delivery can be handled by Grafana or an external Alertmanager.	Alert rule evaluation and alert delivery are distributed.
Scaling	Alert rules are stored in the Grafana database, which may experience transient errors. It only scales vertically.	Alert rules are stored within the data source and allow for horizontal scaling.

Recording rules

Similar to alert rules, recording rules are evaluated periodically. A recording rule pre-computes frequently used or computationally expensive queries, and saves the results as a new time series metric.

The new recording metric can then be used in alert rules and dashboards to optimize their queries.

For more details, refer to Create recording rules.