Documentation Grafana Alloy Reference Components local local.file_match

local.file_match

local.file_match discovers files on the local filesystem using glob patterns and the doublestar library.

Usage

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local.file_match "LABEL" {
  path_targets = [{"__path__" = DOUBLESTAR_PATH}]
}

Arguments

You can use the following arguments with local.file_match:

path_targets structure

Each target in path_targets is a map that can contain the following keys:

The __path__ field uses doublestar style glob patterns:

• /tmp/**/*.log matches all subdirectories of tmp and include any files that end in *.log.
• /tmp/apache/*.log matches only files in /tmp/apache/ that end in *.log.
• /tmp/** matches all subdirectories of tmp, tmp itself, and all files.

local.file_match doesn’t ignore files when you set ignore_older_than to the default, 0s.

When you provide __path_exclude__, the component excludes any files matching the __path__ pattern that also match the __path_exclude__ pattern from the exported list.

The component preserves any additional labels you provide in the path_targets map and includes them in the exported targets alongside the discovered paths. This enables you to add metadata such as service names, instance identifiers, or other contextual information to the discovered files.

Blocks

The local.file_match 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:

Each target includes the following labels:

• __path__: Absolute path to the discovered file.
• All additional labels from the corresponding entry in path_targets with original values preserved.

Component health

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

Debug information

local.file_match doesn’t expose any component-specific debug information.

Debug metrics

local.file_match doesn’t expose any component-specific debug metrics.

Examples

The following examples show you how to use local.file_match to find and send log files to Loki

Send /tmp/logs/*.log files to Loki

This example discovers all files and folders under /tmp/logs except for files in the /tmp/logs/excluded directory. loki.source.file.files targets use absolute paths in the __path__ label.

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local.file_match "tmp" {
  path_targets = [{"__path__" = "/tmp/logs/**/*.log", "__path_exclude__" = "/tmp/logs/excluded/*.log"}]
}

loki.source.file "files" {
  targets    = local.file_match.tmp.targets
  forward_to = [loki.write.endpoint.receiver]
}

loki.write "endpoint" {
  endpoint {
      url = <LOKI_URL>
      basic_auth {
          username = <USERNAME>
          password = <PASSWORD>
      }
  }
}

Replace the following:

• <LOKI_URL>: The URL of the Loki server to send logs to.
• <USERNAME>: The username to use for authentication to the Loki API.
• <PASSWORD>: The password to use for authentication to the Loki API.

Send files with additional labels

This example shows how to include additional labels with discovered files. The component preserves the additional labels in the exported targets and you can use them for filtering or enrichment. It attaches the additional labels instance, job, and service to each discovered file. Downstream components like loki.source.file can access these labels for processing and enrichment.

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Expand code

local.file_match "labeled_logs" {
  path_targets = [
    {
      "__path__"    = "/var/log/apache2/*.log",
      "__address__" = "localhost",
      "instance"    = "web-server-01", 
      "job"         = "apache",
      "service"     = "web"
    },
    {
      "__path__"       = "/var/log/nginx/*.log",
      "__path_exclude__" = "/var/log/nginx/*.gz",
      "__address__"    = "localhost",
      "instance"       = "web-server-01",
      "job"            = "nginx", 
      "service"        = "web"
    }
  ]
}

loki.source.file "web_logs" {
  targets    = local.file_match.labeled_logs.targets
  forward_to = [loki.write.endpoint.receiver]
}

loki.write "endpoint" {
  endpoint {
      url = <LOKI_URL>
      basic_auth {
          username = <USERNAME>
          password = <PASSWORD>
      }
  }
}

Replace the following:

• <LOKI_URL>: The URL of the Loki server to send logs to.
• <USERNAME>: The username to use for authentication to the Loki API.
• <PASSWORD>: The password to use for authentication to the Loki API.

Send Kubernetes Pod logs to Loki

This example finds all the logs on Pods and monitors them.

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Expand code

discovery.kubernetes "k8s" {
  role = "pod"
}

discovery.relabel "k8s" {
  targets = discovery.kubernetes.k8s.targets

  rule {
    source_labels = ["__meta_kubernetes_namespace", "__meta_kubernetes_pod_label_name"]
    target_label  = "job"
    separator     = "/"
  }

  rule {
    source_labels = ["__meta_kubernetes_pod_uid", "__meta_kubernetes_pod_container_name"]
    target_label  = "__path__"
    separator     = "/"
    replacement   = "/var/log/pods/*$1/*.log"
  }
}

local.file_match "pods" {
  path_targets = discovery.relabel.k8s.output
}

loki.source.file "pods" {
  targets = local.file_match.pods.targets
  forward_to = [loki.write.endpoint.receiver]
}

loki.write "endpoint" {
  endpoint {
      url = <LOKI_URL>
      basic_auth {
          username = <USERNAME>
          password = <PASSWORD>
      }
  }
}

Replace the following:

• <LOKI_URL>: The URL of the Loki server to send logs to.
• <USERNAME>: The username to use for authentication to the Loki API.
• <PASSWORD>: The password to use for authentication to the Loki API.

Compatible components

local.file_match can accept arguments from the following components:

• Components that export Targets

local.file_match has exports that can be consumed by the following components:

• Components that consume Targets