discovery.file
General availability (GA)

discovery.file

discovery.file discovers targets from a set of files, similar to the Prometheus file_sd_config.

Usage

alloy
discovery.file "<LABEL>" {
  files = ["<FILE_PATH_1>", "<FILE_PATH_2>", ...]
}

Arguments

You can use the following arguments with discovery.file:

NameTypeDescriptionDefaultRequired
fileslist(string)Files to read and discover targets from.yes
refresh_intervaldurationHow often to sync targets.“5m”no

The last path segment of each element in files may contain a single * that matches any character sequence, for example, my/path/tg_*.json.

Blocks

The discovery.file component doesn’t support any blocks. You can configure this component with arguments.

Exported fields

The following fields are exported and can be referenced by other components:

NameTypeDescription
targetslist(map(string))The set of targets discovered from the filesystem.

Each target includes the following labels:

  • __meta_filepath: The absolute path to the file the target was discovered from.

Component health

discovery.file is only reported as unhealthy when given an invalid configuration. In those cases, exported fields retain their last healthy values.

Debug information

discovery.file doesn’t expose any component-specific debug information.

Debug metrics

discovery.file doesn’t expose any component-specific debug metrics.

Examples

The following examples show you how to configure the discovery.file component.

Example target files

json
[
  {
    "targets": [ "127.0.0.1:9091", "127.0.0.1:9092" ],
    "labels": {
      "environment": "dev"
    }
  },
  {
    "targets": [ "127.0.0.1:9093" ],
    "labels": {
      "environment": "prod"
    }
  }
]
yaml
- targets:
  - 127.0.0.1:9999
  - 127.0.0.1:10101
  labels:
    job: worker
- targets:
  - 127.0.0.1:9090
  labels:
    job: prometheus

Basic file discovery

This example discovers targets from a single file, scrapes them, and writes metrics to a Prometheus remote write endpoint.

alloy
discovery.file "example" {
  files = ["/tmp/example.json"]
}

prometheus.scrape "default" {
  targets    = discovery.file.example.targets
  forward_to = [prometheus.remote_write.demo.receiver]
}

prometheus.remote_write "demo" {
  endpoint {
    url = "<PROMETHEUS_REMOTE_WRITE_URL>"

    basic_auth {
      username = "<USERNAME>"
      password = "<PASSWORD>"
    }
  }
}

Replace the following:

  • <PROMETHEUS_REMOTE_WRITE_URL>: The URL of the Prometheus remote_write-compatible server to send metrics to.
  • <USERNAME>: The username to use for authentication to the remote_write API.
  • <PASSWORD>: The password to use for authentication to the remote_write API.

File discovery with retained file path label

This example discovers targets from a wildcard file path, scrapes them, and writes metrics to a Prometheus remote write endpoint.

It also uses a relabeling rule to retain the file path as a label on each target.

alloy
discovery.file "example" {
  files = ["/tmp/example_*.yaml"]
}

discovery.relabel "keep_filepath" {
  targets = discovery.file.example.targets
  rule {
    source_labels = ["__meta_filepath"]
    target_label = "filepath"
  }
}

prometheus.scrape "default" {
  targets    = discovery.relabel.keep_filepath.output
  forward_to = [prometheus.remote_write.demo.receiver]
}

prometheus.remote_write "demo" {
  endpoint {
    url = <PROMETHEUS_REMOTE_WRITE_URL>

    basic_auth {
      username = <USERNAME>
      password = <PASSWORD>
    }
  }
}

Replace the following:

  • <PROMETHEUS_REMOTE_WRITE_URL>: The URL of the Prometheus remote_write-compatible server to send metrics to.
  • <USERNAME>: The username to use for authentication to the remote_write API.
  • <PASSWORD>: The password to use for authentication to the remote_write API.

Compatible components

discovery.file has exports that can be consumed by the following components:

Note

Connecting some components may not be sensible or components may require further configuration to make the connection work correctly. Refer to the linked documentation for more details.