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Reference

Components

discovery

discovery.kubernetes

Open source

discovery.kubernetes

discovery.kubernetes allows you to find scrape targets from Kubernetes resources. It watches cluster state, and ensures targets are continually synced with what is currently running in your cluster.

If you supply no connection information, this component defaults to an in-cluster configuration. A kubeconfig file or manual connection settings can be used to override the defaults.

Usage

discovery.kubernetes "LABEL" {
  role = DISCOVERY_ROLE
}

Arguments

The following arguments are supported:

Name	Type	Description	Default	Required
`api_server`	`string`	URL of Kubernetes API server.		no
`role`	`string`	Type of Kubernetes resource to query.		yes
`kubeconfig_file`	`string`	Path of kubeconfig file to use for connecting to Kubernetes.		no
`bearer_token_file`	`string`	File containing a bearer token to authenticate with.		no
`bearer_token`	`secret`	Bearer token to authenticate with.		no
`enable_http2`	`bool`	Whether HTTP2 is supported for requests.	`true`	no
`follow_redirects`	`bool`	Whether redirects returned by the server should be followed.	`true`	no
`proxy_url`	`string`	HTTP proxy to send requests through.		no
`no_proxy`	`string`	Comma-separated list of IP addresses, CIDR notations, and domain names to exclude from proxying.		no
`proxy_from_environment`	`bool`	Use the proxy URL indicated by environment variables.	`false`	no
`proxy_connect_header`	`map(list(secret))`	Specifies headers to send to proxies during CONNECT requests.		no

At most, one of the following can be provided:

bearer_token argument.
bearer_token_file argument.
basic_auth block.
authorization block.
oauth2 block.

no_proxy can contain IPs, CIDR notations, and domain names. IP and domain names can contain port numbers. proxy_url must be configured if no_proxy is configured.

proxy_from_environment uses the environment variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY (or the lowercase versions thereof). Requests use the proxy from the environment variable matching their scheme, unless excluded by NO_PROXY. proxy_url and no_proxy must not be configured if proxy_from_environment is configured.

proxy_connect_header should only be configured if proxy_url or proxy_from_environment are configured.

The role argument is required to specify what type of targets to discover. role must be one of node, pod, service, endpoints, endpointslice, or ingress.

node role

The node role discovers one target per cluster node with the address defaulting to the HTTP port of the Kubelet daemon. The target address defaults to the first existing address of the Kubernetes node object in the address type order of NodeInternalIP, NodeExternalIP, NodeLegacyHostIP, and NodeHostName.

The following labels are included for discovered nodes:

__meta_kubernetes_node_name: The name of the node object.
__meta_kubernetes_node_provider_id: The cloud provider’s name for the node object.
__meta_kubernetes_node_label_<labelname>: Each label from the node object.
__meta_kubernetes_node_labelpresent_<labelname>: Set to true for each label from the node object.
__meta_kubernetes_node_annotation_<annotationname>: Each annotation from the node object.
__meta_kubernetes_node_annotationpresent_<annotationname>: Set to true for each annotation from the node object.
__meta_kubernetes_node_address_<address_type>: The first address for each node address type, if it exists.

In addition, the instance label for the node will be set to the node name as retrieved from the API server.

service role

The service role discovers a target for each service port for each service. This is generally useful for externally monitoring a service. The address will be set to the Kubernetes DNS name of the service and respective service port.

The following labels are included for discovered services:

__meta_kubernetes_namespace: The namespace of the service object.
__meta_kubernetes_service_annotation_<annotationname>: Each annotation from the service object.
__meta_kubernetes_service_annotationpresent_<annotationname>: true for each annotation of the service object.
__meta_kubernetes_service_cluster_ip: The cluster IP address of the service. This does not apply to services of type ExternalName.
__meta_kubernetes_service_external_name: The DNS name of the service. This only applies to services of type ExternalName.
__meta_kubernetes_service_label_<labelname>: Each label from the service object.
__meta_kubernetes_service_labelpresent_<labelname>: true for each label of the service object.
__meta_kubernetes_service_name: The name of the service object.
__meta_kubernetes_service_port_name: Name of the service port for the target.
__meta_kubernetes_service_port_number: Number of the service port for the target.
__meta_kubernetes_service_port_protocol: Protocol of the service port for the target.
__meta_kubernetes_service_type: The type of the service.

pod role

The pod role discovers all pods and exposes their containers as targets. For each declared port of a container, a single target is generated.

If a container has no specified ports, a port-free target per container is created. These targets must have a port manually injected using a discovery.relabel component before metrics can be collected from them.

The following labels are included for discovered pods:

__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.

endpoints role

The endpoints role discovers targets from listed endpoints of a service. For each endpoint address one target is discovered per port. If the endpoint is backed by a pod, all container ports of a pod are discovered as targets even if they are not bound to an endpoint port.

The following labels are included for discovered endpoints:

__meta_kubernetes_namespace: The namespace of the endpoints object.
__meta_kubernetes_endpoints_name: The names of the endpoints object.
__meta_kubernetes_endpoints_label_<labelname>: Each label from the endpoints object.
__meta_kubernetes_endpoints_labelpresent_<labelname>: true for each label from the endpoints object.
The following labels are attached for all targets discovered directly from the endpoints list:
- __meta_kubernetes_endpoint_hostname: Hostname of the endpoint.
- __meta_kubernetes_endpoint_node_name: Name of the node hosting the endpoint.
- __meta_kubernetes_endpoint_ready: Set to true or false for the endpoint’s ready state.
- __meta_kubernetes_endpoint_port_name: Name of the endpoint port.
- __meta_kubernetes_endpoint_port_protocol: Protocol of the endpoint port.
- __meta_kubernetes_endpoint_address_target_kind: Kind of the endpoint address target.
- __meta_kubernetes_endpoint_address_target_name: Name of the endpoint address target.
If the endpoints belong to a service, all labels of the service role discovery are attached.
For all targets backed by a pod, all labels of the pod role discovery are attached.

endpointslice role

The endpointslice role discovers targets from existing Kubernetes endpoint slices. For each endpoint address referenced in the EndpointSlice object, one target is discovered. If the endpoint is backed by a Pod, all container ports of a Pod are discovered as targets even if they are not bound to an endpoint port.

The following labels are included for discovered endpoint slices:

__meta_kubernetes_namespace: The namespace of the endpoints object.
__meta_kubernetes_endpointslice_name: The name of endpoint slice object.
The following labels are attached for all targets discovered directly from the endpoint slice list:
- __meta_kubernetes_endpointslice_address_target_kind: Kind of the referenced object.
- __meta_kubernetes_endpointslice_address_target_name: Name of referenced object.
- __meta_kubernetes_endpointslice_address_type: The IP protocol family of the address of the target.
- __meta_kubernetes_endpointslice_endpoint_conditions_ready: Set to true or false for the referenced endpoint’s ready state.
- __meta_kubernetes_endpointslice_endpoint_topology_kubernetes_io_hostname: Name of the node hosting the referenced endpoint.
- __meta_kubernetes_endpointslice_endpoint_topology_present_kubernetes_io_hostname: true if the referenced object has a kubernetes.io/hostname annotation.
- __meta_kubernetes_endpointslice_port: Port of the referenced endpoint.
- __meta_kubernetes_endpointslice_port_name: Named port of the referenced endpoint.
- __meta_kubernetes_endpointslice_port_protocol: Protocol of the referenced endpoint.
If the endpoints belong to a service, all labels of the service role discovery are attached.
For all targets backed by a pod, all labels of the pod role discovery are attached.

ingress role

The ingress role discovers a target for each path of each ingress. This is generally useful for externally monitoring an ingress. The address will be set to the host specified in the Kubernetes Ingress’s spec block.

The following labels are included for discovered ingress objects:

__meta_kubernetes_namespace: The namespace of the ingress object.
__meta_kubernetes_ingress_name: The name of the ingress object.
__meta_kubernetes_ingress_label_<labelname>: Each label from the ingress object.
__meta_kubernetes_ingress_labelpresent_<labelname>: true for each label from the ingress object.
__meta_kubernetes_ingress_annotation_<annotationname>: Each annotation from the ingress object.
__meta_kubernetes_ingress_annotationpresent_<annotationname>: true for each annotation from the ingress object.
__meta_kubernetes_ingress_class_name: Class name from ingress spec, if present.
__meta_kubernetes_ingress_scheme: Protocol scheme of ingress, https if TLS config is set. Defaults to http.
__meta_kubernetes_ingress_path: Path from ingress spec. Defaults to /.

Blocks

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

Hierarchy	Block	Description	Required
namespaces	namespaces	Information about which Kubernetes namespaces to search.	no
selectors	selectors	Selectors to filter discovered Kubernetes resources.	no
attach_metadata	attach_metadata	Optional metadata to attach to discovered targets.	no
basic_auth	basic_auth	Configure basic_auth for authenticating to the endpoint.	no
authorization	authorization	Configure generic authorization to the endpoint.	no
oauth2	oauth2	Configure OAuth2 for authenticating to the endpoint.	no
oauth2 > tls_config	tls_config	Configure TLS settings for connecting to the endpoint.	no
tls_config	tls_config	Configure TLS settings for connecting to the endpoint.	no

The > symbol indicates deeper levels of nesting. For example, oauth2 > tls_config refers to a tls_config block defined inside an oauth2 block.

namespaces block

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

Name	Type	Description	Default	Required
`own_namespace`	`bool`	Include the namespace Alloy is running in.		no
`names`	`list(string)`	List of namespaces to search.		no

selectors block

The selectors block contains optional label and field selectors to limit the discovery process to a subset of resources.

Name	Type	Description	Required
`role`	`string`	Role of the selector.	yes
`label`	`string`	Label selector string.	no
`field`	`string`	Field selector string.	no

See Kubernetes’ documentation for Field selectors and Labels and selectors to learn more about the possible filters that can be used.

The endpoints role supports Pod, service, and endpoints selectors. The Pod role supports node selectors when configured with attach_metadata: {node: true}. Other roles only support selectors matching the role itself (e.g. node role can only contain node selectors).

Note
Using multiple discovery.kubernetes components with different selectors may result in a bigger load against the Kubernetes API.
Selectors are recommended for retrieving a small set of resources in a very large cluster. Smaller clusters are recommended to avoid selectors in favor of filtering with a discovery.relabel component instead.

attach_metadata block

The attach_metadata block allows to attach node metadata to discovered targets. Valid for roles: pod, endpoints, endpointslice.

Name	Type	Description	Default	Required
`node`	`bool`	Attach node metadata.		no

basic_auth block

Name	Type	Description	Required
`password_file`	`string`	File containing the basic auth password.	no
`password`	`secret`	Basic auth password.	no
`username`	`string`	Basic auth username.	no

password and password_file are mutually exclusive, and only one can be provided inside a basic_auth block.

authorization block

Name	Type	Description	Required
`credentials_file`	`string`	File containing the secret value.	no
`credentials`	`secret`	Secret value.	no
`type`	`string`	Authorization type, for example, “Bearer”.	no

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

oauth2 block

Name	Type	Description	Default	Required
`client_id`	`string`	OAuth2 client ID.		no
`client_secret_file`	`string`	File containing the OAuth2 client secret.		no
`client_secret`	`secret`	OAuth2 client secret.		no
`endpoint_params`	`map(string)`	Optional parameters to append to the token URL.		no
`proxy_url`	`string`	HTTP proxy to send requests through.		no
`no_proxy`	`string`	Comma-separated list of IP addresses, CIDR notations, and domain names to exclude from proxying.		no
`proxy_from_environment`	`bool`	Use the proxy URL indicated by environment variables.	`false`	no
`proxy_connect_header`	`map(list(secret))`	Specifies headers to send to proxies during CONNECT requests.		no
`scopes`	`list(string)`	List of scopes to authenticate with.		no
`token_url`	`string`	URL to fetch the token from.		no

client_secret and client_secret_file are mutually exclusive, and only one can be provided inside an oauth2 block.

The oauth2 block may also contain a separate tls_config sub-block.

no_proxy can contain IPs, CIDR notations, and domain names. IP and domain names can contain port numbers. proxy_url must be configured if no_proxy is configured.

proxy_connect_header should only be configured if proxy_url or proxy_from_environment are configured.

tls_config block

Name	Type	Description	Required
`ca_pem`	`string`	CA PEM-encoded text to validate the server with.	no
`ca_file`	`string`	CA certificate to validate the server with.	no
`cert_pem`	`string`	Certificate PEM-encoded text for client authentication.	no
`cert_file`	`string`	Certificate file for client authentication.	no
`insecure_skip_verify`	`bool`	Disables validation of the server certificate.	no
`key_file`	`string`	Key file for client authentication.	no
`key_pem`	`secret`	Key PEM-encoded text for client authentication.	no
`min_version`	`string`	Minimum acceptable TLS version.	no
`server_name`	`string`	ServerName extension to indicate the name of the server.	no

The following pairs of arguments are mutually exclusive and can’t 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:

Name	Type	Description
`targets`	`list(map(string))`	The set of targets discovered from the Kubernetes API.

Component health

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

Debug information

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

Debug metrics

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

Examples

In-cluster discovery

This example uses in-cluster authentication to discover all pods:

discovery.kubernetes "k8s_pods" {
  role = "pod"
}

prometheus.scrape "demo" {
  targets    = discovery.kubernetes.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.

Kubeconfig authentication

This example uses a Kubeconfig file to authenticate to the Kubernetes API:

discovery.kubernetes "k8s_pods" {
  role = "pod"
  kubeconfig_file = "/etc/k8s/kubeconfig.yaml"
}

prometheus.scrape "demo" {
  targets    = discovery.kubernetes.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 and filter by labels value

This example limits the searched namespaces and only selects pods with a specific label value attached to them:

discovery.kubernetes "k8s_pods" {
  role = "pod"

  selectors {
    role = "pod"
    label = "app.kubernetes.io/name=prometheus-node-exporter"
  }

  namespaces {
    names = ["myapp"]
  }
}

prometheus.scrape "demo" {
  targets    = discovery.kubernetes.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 to only pods on the same node

This example limits the search to pods on the same node as this Alloy. This configuration could be useful if you are running Alloy as a DaemonSet.

Note
This example assumes you have used Helm chart to deploy Alloy in Kubernetes and sets HOSTNAME to the Kubernetes host name. If you have a custom Kubernetes Deployment, you must adapt this example to your configuration.

discovery.kubernetes "k8s_pods" {
  role = "pod"
  selectors {
    role = "pod"
    field = "spec.nodeName=" + coalesce(env("HOSTNAME"), constants.hostname)
  }
}

prometheus.scrape "demo" {
  targets    = discovery.kubernetes.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.

Compatible components

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

Components that consume Targets

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.

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Feedback

discovery.kubernetes

Usage

Arguments

node role

service role

pod role

endpoints role

endpointslice role

ingress role

Blocks

namespaces block

selectors block

attach_metadata block

basic_auth block

authorization block

oauth2 block

tls_config block

Exported fields

Component health

Debug information

Debug metrics

Examples

In-cluster discovery

Kubeconfig authentication

Limit searched namespaces and filter by labels value

Limit to only pods on the same node

Compatible components

Was this page helpful?

Related documentation

discovery.kubernetes

Usage

Arguments

node role

service role

pod role

endpoints role

endpointslice role

ingress role

Blocks

namespaces block

selectors block

attach_metadata block

basic_auth block

authorization block

oauth2 block

tls_config block

Exported fields

Component health

Debug information

Debug metrics

Examples

In-cluster discovery

Kubeconfig authentication

Limit searched namespaces and filter by labels value

Limit to only pods on the same node

Compatible components

Was this page helpful?

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