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Caution

Grafana Alloy is the new name for our distribution of the OTel collector. Grafana Agent has been deprecated and is in Long-Term Support (LTS) through October 31, 2025. Grafana Agent will reach an End-of-Life (EOL) on November 1, 2025. Read more about why we recommend migrating to Grafana Alloy.

Important: This documentation is about an older version. It's relevant only to the release noted, many of the features and functions have been updated or replaced. Please view the current version.

Beta

discovery.kubelet

discovery.kubelet discovers Kubernetes pods running on the specified Kubelet and exposes them as scrape targets.

Usage

river
discovery.kubelet "LABEL" {
}

Requirements

  • The Kubelet must be reachable from the grafana-agent pod network.
  • Follow the Kubelet authorization documentation to configure authentication to the Kubelet API.

Arguments

The following arguments are supported:

NameTypeDescriptionDefaultRequired
urlstringURL of the Kubelet server.no
bearer_tokensecretBearer token to authenticate with.no
bearer_token_filestringFile containing a bearer token to authenticate with.no
refresh_intervaldurationHow often the Kubelet should be polled for scrape targets5sno
namespaceslist(string)A list of namespaces to extract target pods fromno

One of the following authentication methods must be provided if kubelet authentication is enabled

The namespaces list limits the namespaces to discover resources in. If omitted, all namespaces are searched.

Blocks

The following blocks are supported inside the definition of discovery.kubelet:

HierarchyBlockDescriptionRequired
authorizationauthorizationConfigure generic authorization to the endpoint.no
tls_configtls_configConfigure TLS settings for connecting to the endpoint.no

authorization block

NameTypeDescriptionDefaultRequired
typestringAuthorization type, for example, “Bearer”.no
credentialssecretSecret value.no
credentials_filestringFile containing the secret value.no

credential and credentials_file are mutually exclusive and only one can be provided inside of an authorization block.

tls_config block

NameTypeDescriptionDefaultRequired
ca_pemstringCA PEM-encoded text to validate the server with.no
ca_filestringCA certificate to validate the server with.no
cert_pemstringCertificate PEM-encoded text for client authentication.no
cert_filestringCertificate file for client authentication.no
key_pemsecretKey PEM-encoded text for client authentication.no
key_filestringKey file for client authentication.no
server_namestringServerName extension to indicate the name of the server.no
insecure_skip_verifyboolDisables validation of the server certificate.no
min_versionstringMinimum acceptable TLS version.no

The following pairs of arguments are mutually exclusive and cannot both be set simultaneously:

  • ca_pem and ca_file
  • cert_pem and cert_file
  • key_pem and key_file

When configuring client authentication, both the client certificate (using cert_pem or cert_file) and the client key (using key_pem or key_file) must be provided.

When min_version is not provided, the minimum acceptable TLS version is inherited from Go’s default minimum version, TLS 1.2. If min_version is provided, it must be set to one of the following strings:

  • "TLS10" (TLS 1.0)
  • "TLS11" (TLS 1.1)
  • "TLS12" (TLS 1.2)
  • "TLS13" (TLS 1.3)

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 Kubelet API.

Each target includes the following labels:

  • __address__: The target address to scrape derived from the pod IP and container port.
  • __meta_kubernetes_namespace: The namespace of the pod object.
  • __meta_kubernetes_pod_name: The name of the pod object.
  • __meta_kubernetes_pod_ip: The pod IP of the pod object.
  • __meta_kubernetes_pod_label_<labelname>: Each label from the pod object.
  • __meta_kubernetes_pod_labelpresent_<labelname>: true for each label from the pod object.
  • __meta_kubernetes_pod_annotation_<annotationname>: Each annotation from the pod object.
  • __meta_kubernetes_pod_annotationpresent_<annotationname>: true for each annotation from the pod object.
  • __meta_kubernetes_pod_container_init: true if the container is an InitContainer.
  • __meta_kubernetes_pod_container_name: Name of the container the target address points to.
  • __meta_kubernetes_pod_container_id: ID of the container the target address points to. The ID is in the form <type>://<container_id>.
  • __meta_kubernetes_pod_container_image: The image the container is using.
  • __meta_kubernetes_pod_container_port_name: Name of the container port.
  • __meta_kubernetes_pod_container_port_number: Number of the container port.
  • __meta_kubernetes_pod_container_port_protocol: Protocol of the container port.
  • __meta_kubernetes_pod_ready: Set to true or false for the pod’s ready state.
  • __meta_kubernetes_pod_phase: Set to Pending, Running, Succeeded, Failed or Unknown in the lifecycle.
  • __meta_kubernetes_pod_node_name: The name of the node the pod is scheduled onto.
  • __meta_kubernetes_pod_host_ip: The current host IP of the pod object.
  • __meta_kubernetes_pod_uid: The UID of the pod object.
  • __meta_kubernetes_pod_controller_kind: Object kind of the pod controller.
  • __meta_kubernetes_pod_controller_name: Name of the pod controller.

Note: The Kubelet API used by this component is an internal API and therefore the data in the response returned from the API cannot be guaranteed between different versions of the Kubelet.

Component health

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

Debug information

discovery.kubelet does not expose any component-specific debug information.

Debug metrics

discovery.kubelet does not expose any component-specific debug metrics.

Examples

Bearer token file authentication

This example uses a bearer token file to authenticate to the Kubelet API:

river
discovery.kubelet "k8s_pods" {
  bearer_token_file = "/var/run/secrets/kubernetes.io/serviceaccount/token"
}

prometheus.scrape "demo" {
  targets    = discovery.kubelet.k8s_pods.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.

Limit searched namespaces

This example limits the namespaces where pods are discovered using the namespaces argument:

river
discovery.kubelet "k8s_pods" {
  bearer_token_file = "/var/run/secrets/kubernetes.io/serviceaccount/token"
  namespaces = ["default", "kube-system"]
}

prometheus.scrape "demo" {
  targets    = discovery.kubelet.k8s_pods.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.