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Grafana Alloy

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Components

loki

loki.source.kubernetes

Grafana Cloud

loki.source.kubernetes

loki.source.kubernetes tails logs from Kubernetes containers using the Kubernetes API.

Note
This component collects logs from Kubernetes Pods. You can’t use this component to collect logs from Kubernetes Nodes.

This component has the following benefits over loki.source.file:

It works without a privileged container.
It works without a root user.
It works without needing access to the filesystem of the Kubernetes node.
It doesn’t require a DaemonSet to collect logs, so one Alloy could collect logs for the whole cluster.

Note
Because loki.source.kubernetes uses the Kubernetes API to tail logs, it uses more network traffic and CPU consumption of Kubelets than loki.source.file.

You can specify multiple loki.source.kubernetes components by giving them different labels.

Usage

loki.source.kubernetes "LABEL" {
  targets    = TARGET_LIST
  forward_to = RECEIVER_LIST
}

Arguments

The component starts a new reader for each of the given targets and fans out log entries to the list of receivers passed in forward_to.

loki.source.kubernetes supports the following arguments:

Name	Type	Description	Default	Required
`targets`	`list(map(string))`	List of files to read from.		yes
`forward_to`	`list(LogsReceiver)`	List of receivers to send log entries to.		yes

Each target in targets must have the following labels:

__meta_kubernetes_namespace or __pod_namespace__ to specify the namespace of the pod to tail.
__meta_kubernetes_pod_name or __pod_name__ to specify the name of the pod to tail.
__meta_kubernetes_pod_container_name or __pod_container_name__ to specify the container within the pod to tail.
__meta_kubernetes_pod_uid or __pod_uid__ to specify the UID of the pod to tail.

By default, all of these labels are present when the output discovery.kubernetes is used.

A log tailer is started for each unique target in targets. Log tailers will reconnect with exponential backoff to Kubernetes if the log stream returns before the container has permanently terminated.

Blocks

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

Hierarchy	Block	Description	Required
client	client	Configures Kubernetes client used to tail logs.	no
client > basic_auth	basic_auth	Configure `basic_auth` for authenticating to the endpoint.	no
client > authorization	authorization	Configure generic authorization to the endpoint.	no
client > oauth2	oauth2	Configure OAuth2 for authenticating to the endpoint.	no
client > oauth2 > tls_config	tls_config	Configure TLS settings for connecting to the endpoint.	no
client > tls_config	tls_config	Configure TLS settings for connecting to the endpoint.	no
clustering	clustering	Configure the component for when Alloy is running in clustered mode.	no

The > symbol indicates deeper levels of nesting. For example, client > basic_auth refers to a basic_auth block defined inside a client block.

client block

The client block configures the Kubernetes client used to tail logs from containers. If the client block isn’t provided, the default in-cluster configuration with the service account of the running Alloy pod is used.

The following arguments are supported:

Name	Type	Description	Default	Required
`api_server`	`string`	URL of the Kubernetes API server.		no
`kubeconfig_file`	`string`	Path of the `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.

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 isn’t 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)

clustering block

Name	Type	Description	Default	Required
`enabled`	`bool`	Distribute log collection with other cluster nodes.		yes

When Alloy is using clustering, and enabled is set to true, then this loki.source.kubernetes component instance opts-in to participating in the cluster to distribute the load of log collection between all cluster nodes.

If Alloy is not running in clustered mode, then the block is a no-op and loki.source.kubernetes collects logs from every target it receives in its arguments.

Clustering looks only at the following labels for determining the shard key:

__pod_namespace__
__pod_name__
__pod_container_name__
__pod_uid__
__meta_kubernetes_namespace
__meta_kubernetes_pod_name
__meta_kubernetes_pod_container_name
__meta_kubernetes_pod_uid
container
pod
job
namespace

Exported fields

loki.source.kubernetes doesn’t export any fields.

Component health

loki.source.kubernetes is only reported as unhealthy if given an invalid configuration.

Debug information

loki.source.kubernetes exposes some target-level debug information per target:

The labels associated with the target.
The full set of labels which were found during service discovery.
The most recent time a log line was read and forwarded to the next components in the pipeline.
The most recent error from tailing, if any.

Debug metrics

loki.source.kubernetes does not expose any component-specific debug metrics.

Example

This example collects logs from all Kubernetes Pods and forwards them to a loki.write component so they are written to Loki.

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

loki.source.kubernetes "pods" {
  targets    = discovery.kubernetes.pods.targets
  forward_to = [loki.write.local.receiver]
}

loki.write "local" {
  endpoint {
    url = sys.env("LOKI_URL")
  }
}

Compatible components

loki.source.kubernetes can accept arguments from the following components:

Components that export Targets
Components that export Loki LogsReceiver

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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