Documentation Grafana Alloy Reference Components loki loki.source.podlogs

loki.source.podlogs

loki.source.podlogs discovers PodLogs resources on Kubernetes. The PodLogs resources provide rules for which Kubernetes Pods to discover on your cluster.

loki.source.podlogs uses the Kubernetes API to tail the logs from the discovered Kubernetes Pods.

loki.source.podlogs is similar to loki.source.kubernetes, but uses custom resources rather than being fed targets from another component.

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

Usage

alloy Copy

loki.source.podlogs "<LABEL>" {
  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.

You can use the following arguments with loki.source.podlogs:

loki.source.podlogs searches for PodLogs resources on Kubernetes. Each PodLogs resource describes a set of pods to tail logs from.

When tail_from_end is false (the default), loki.source.podlogs reads all available logs from the Kubernetes API for newly discovered Pod containers. For long-running Pods, this can result in a large volume of logs being processed, which may be rejected by the downstream Loki instance if they are too old. Set tail_from_end to true to only read new logs from the point of discovery, ignoring the historical log buffer. If a last-read offset is already saved for a Pod, loki.source.podlogs will resume from that position and ignore the tail_from_end argument.

PodLogs custom resource

The PodLogs resource describes a set of Pods to collect logs from.

PodLogsSpec

PodLogsSpec describes a set of Pods to collect logs from.

If selector is left as the default value, all Pods are discovered. If namespaceSelector is left as the default value, all Namespaces are used for Pod discovery.

The relabelings field can be used to modify labels from discovered Pods. The following meta labels are available for relabeling:

• __meta_kubernetes_namespace: The namespace of the Pod.
• __meta_kubernetes_pod_annotation_<annotationname>: Each annotation from the Pod.
• __meta_kubernetes_pod_annotationpresent_<annotationname>: true for each annotation from the Pod.
• __meta_kubernetes_pod_container_image: The image the container is using.
• __meta_kubernetes_pod_container_init: true if the container is an InitContainer.
• __meta_kubernetes_pod_container_name: Name of the container.
• __meta_kubernetes_pod_controller_kind: Object kind of the Pod’s controller.
• __meta_kubernetes_pod_controller_name: Name of the Pod’s controller.
• __meta_kubernetes_pod_host_ip: The current host IP of the Pod object.
• __meta_kubernetes_pod_ip: The Pod IP of the Pod.
• __meta_kubernetes_pod_label_<labelname>: Each label from the Pod.
• __meta_kubernetes_pod_labelpresent_<labelname>: true for each label from the Pod.
• __meta_kubernetes_pod_name: The name of the Pod.
• __meta_kubernetes_pod_node_name: The name of the node the Pod is scheduled onto.
• __meta_kubernetes_pod_phase: Set to Pending, Running, Succeeded, Failed or Unknown in the lifecycle.
• __meta_kubernetes_pod_ready: Set to true or false for the Pod’s ready state.
• __meta_kubernetes_pod_uid: The UID of the Pod.

In addition to the meta labels, the following labels are exposed to tell loki.source.podlogs which container to tail:

• __pod_container_name__: The container name within the Pod.
• __pod_name__: The name of the Pod.
• __pod_namespace__: The namespace of the Pod.
• __pod_uid__: The UID of the Pod.

Blocks

You can use the following blocks with loki.source.podlogs:

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

client

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:

At most, one of the following can be provided:

• authorization block
• basic_authblock
• bearer_token_file argument
• bearer_token argument
• oauth2 block

authorization

basic_auth

clustering

When Alloy is using clustering, and enabled is set to true, then this loki.source.podlogs 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.podlogs collects logs based on every PodLogs resource discovered.

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

node_filter

The node_filter block configures node-based filtering for Pod discovery.

The following arguments are supported:

When you set enabled to true, loki.source.podlogs only discovers and collects logs from Pods running on the specified node. This is particularly useful when running Alloy as a DaemonSet to avoid collecting logs from Pods on other nodes.

If you don’t specify node_name, loki.source.podlogs attempts to use the NODE_NAME environment variable. This allows for easy configuration in DaemonSet deployments where you can inject the node name with the Kubernetes downward API.

Example DaemonSet configuration:

YAML Copy

env:
  - name: NODE_NAME
    valueFrom:
      fieldRef:
        fieldPath: spec.nodeName

Node filtering significantly reduces API server load and network traffic by limiting Pod discovery to only the local node, making it highly recommended for DaemonSet deployments in large clusters.

match_expression

The match_expression block describes a Kubernetes label match expression for PodLogs or Namespace discovery.

The following arguments are supported:

The operator argument must be one of the following strings:

• "In"
• "NotIn"
• "Exists"
• "DoesNotExist"

Both selector and namespace_selector can make use of multiple match_expression inner blocks which are treated as AND clauses.

oauth2

selector and namespace_selector

The selector and namespce_selector blocks describe a Kubernetes label selector for PodLogs or Namespace discovery.

The following arguments are supported:

When the match_labels argument is empty, all resources are matched.

tls_config

Exported fields

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

Component health

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

Debug information

loki.source.podlogs 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.podlogs doesn’t expose any component-specific debug metrics.

Example

This example discovers all PodLogs resources and forwards collected logs to a loki.write component so they’re written to Loki.

alloy Copy

loki.source.podlogs "default" {
  forward_to = [loki.write.local.receiver]
}

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

This example shows how to use node filtering for DaemonSet deployments to collect logs only from Pods running on the current node:

alloy Copy

loki.source.podlogs "daemonset" {
  forward_to = [loki.write.local.receiver]
  
  node_filter {
    enabled = true
    // node_name will be automatically read from NODE_NAME environment variable
  }
}

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

Compatible components

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

• Components that export Loki LogsReceiver