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Documentation Grafana Agent Flow mode Concepts Configuration language concepts

Configuration language concepts

The Grafana Agent Flow configuration language, River, refers to the language used in configuration files that define and configure components to run.

river Copy

prometheus.scrape "default" {
  targets = [{
    "__address__" = "demo.robustperception.io:9090",
  }]
  forward_to = [prometheus.remote_write.default.receiver]
}

prometheus.remote_write "default" {
  endpoint {
    url = "http://localhost:9009/api/prom/push"
  }
}

River is designed with the following requirements in mind:

• Fast: The configuration language must be fast so the component controller can quickly evaluate changes.
• Simple: The configuration language must be easy to read and write to minimize the learning curve.
• Debuggable: The configuration language must give detailed information when there’s a mistake in the configuration file.

Attributes

You use Attributes to configure individual settings. Attributes always take the form of ATTRIBUTE_NAME = ATTRIBUTE_VALUE.

The following example shows how to set the log_level attribute to "debug".

river Copy

log_level = "debug"

Expressions

You use expressions to compute the value of an attribute. The simplest expressions are constant values like "debug", 32, or [1, 2, 3, 4]. River supports complex expressions, for example:

• Referencing the exports of components: local.file.password_file.content
• Mathematical operations: 1 + 2, 3 * 4, (5 * 6) + (7 + 8)
• Equality checks: local.file.file_a.content == local.file.file_b.content
• Calling functions from River’s standard library: env("HOME") retrieves the value of the HOME environment variable.

You can use expressions for any attribute inside a component definition.

Referencing component exports

The most common expression is to reference the exports of a component, for example, local.file.password_file.content. You form a reference to a component’s exports by merging the component’s name (for example, local.file), label (for example, password_file), and export name (for example, content), delimited by a period.

Blocks

You use Blocks to configure components and groups of attributes. Each block can contain any number of attributes or nested blocks.

river Copy

prometheus.remote_write "default" {
  endpoint {
    url = "http://localhost:9009/api/prom/push"
  }
}

The preceding example has two blocks:

• prometheus.remote_write "default": A labeled block which instantiates a prometheus.remote_write component. The label is the string "default".
• endpoint: An unlabeled block inside the component that configures an endpoint to send metrics to. This block sets the url attribute to specify the endpoint.

More information

Refer to Configuration language for more information about River.