fluent-plugin-kubernetes_metadata_filter, a plugin for Fluentd

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The Kubernetes metadata plugin filter enriches container log records with pod and namespace metadata.

This plugin derives basic metadata about the container that emitted a given log record using the source of the log record. Records from kubernetes containers encode metadata about the container in the file name. The initial metadata derived from the source is used to lookup additional metadata about the container's associated pod and namespace (e.g. UUIDs, labels, annotations) when the kubernetes_url is configured. If the plugin cannot authoritatively determine the namespace of the container emitting a log record, it will use an 'orphan' namespace ID in the metadata. This behaviors supports multi-tenant systems that rely on the authenticity of the namespace for proper log isolation.


fluent-plugin-kubernetes_metadata_filter fluentd ruby
>= 2.10.0 >= v1.10.0 >= 2.6
>= 2.5.0 >= v1.10.0 >= 2.5
>= 2.0.0 >= v0.14.20 >= 2.1
< 2.0.0 >= v0.12.0 >= 1.9

NOTE: For v0.12 version, you should use 1.x.y version. Please send patch into v0.12 branch if you encountered 1.x version's bug.

NOTE: This documentation is for fluent-plugin-kubernetes_metadata_filter-plugin-elasticsearch 2.x or later. For 1.x documentation, please see v0.12 branch.


gem install fluent-plugin-


Configuration options for fluent.conf are:

  • kubernetes_url - URL to the API server. Set this to retrieve further kubernetes metadata for logs from kubernetes API server. If not specified, environment variables KUBERNETES_SERVICE_HOST and KUBERNETES_SERVICE_PORT will be used if both are present which is typically true when running fluentd in a pod.
  • apiVersion - API version to use (default: v1)
  • ca_file - path to CA file for Kubernetes server certificate validation
  • verify_ssl - validate SSL certificates (default: true)
  • client_cert - path to a client cert file to authenticate to the API server
  • client_key - path to a client key file to authenticate to the API server
  • bearer_token_file - path to a file containing the bearer token to use for authentication
  • tag_to_kubernetes_name_regexp - the regular expression used to extract kubernetes metadata (pod name, container name, namespace) from the current fluentd tag. This must use named capture groups for container_name, pod_name, namespace, and either pod_uuid (/var/log/pods) or docker_id (/var/log/containers)
  • cache_size - size of the cache of Kubernetes metadata to reduce requests to the API server (default: 1000)
  • cache_ttl - TTL in seconds of each cached element. Set to negative value to disable TTL eviction (default: 3600 - 1 hour)
  • watch - set up a watch on pods on the API server for updates to metadata (default: true)
  • annotation_match - Array of regular expressions matching annotation field names. Matched annotations are added to a log record.
  • allow_orphans - Modify the namespace and namespace id to the values of orphaned_namespace_name and orphaned_namespace_id when true (default: true)
  • orphaned_namespace_name - The namespace to associate with records where the namespace can not be determined (default: .orphaned)
  • orphaned_namespace_id - The namespace id to associate with records where the namespace can not be determined (default: orphaned)
  • lookup_from_k8s_field - If the field kubernetes is present, lookup the metadata from the given subfields such as kubernetes.namespace_name, kubernetes.pod_name, etc. This allows you to avoid having to pass in metadata to lookup in an explicitly formatted tag name or in an explicitly formatted CONTAINER_NAME value. For example, set kubernetes.namespace_name, kubernetes.pod_name, kubernetes.container_name, and docker.id in the record, and the filter will fill in the rest. (default: true)
  • ssl_partial_chain - if ca_file is for an intermediate CA, or otherwise we do not have the root CA and want to trust the intermediate CA certs we do have, set this to true - this corresponds to the openssl s_client -partial_chain flag and X509_V_FLAG_PARTIAL_CHAIN (default: false)
  • skip_labels - Skip all label fields from the metadata.
  • skip_pod_labels - Skip only pod label fields from the metadata.
  • skip_namespace_labels - Skip only namespace label fields from the metadata.
  • skip_container_metadata - Skip some of the container data of the metadata. The metadata will not contain the container_image and container_image_id fields.
  • skip_master_url - Skip the master_url field from the metadata.
  • skip_namespace_metadata - Skip the namespace_id field from the metadata. The fetch_namespace_metadata function will be skipped. The plugin will be faster and cpu consumption will be less.
  • stats_interval - The interval to display cache stats (default: 30s). Set to 0 to disable stats collection and logging
  • watch_retry_interval - The time interval in seconds for retry backoffs when watch connections fail. (default: 10)
  • open_timeout - The time in seconds to wait for a connection to kubernetes service. (default: 3)
  • read_timeout - The time in seconds to wait for a read from kubernetes service. (default: 10)
  • include_ownerrefs_metadata - If set to true, it will include metadata (kind & name) in kubernetes.ownerrefs about the controller that owns the pod. (default: false)

Reading from a JSON formatted log files with in_tail and wildcard filenames while respecting the CRI-o log format with the same config you need the fluent-plugin "multi-format-parser":

fluent-gem install fluent-plugin-multi-format-parser

The config block could look like this:

  @type tail
  path /var/log/containers/*.log
  pos_file fluentd-docker.pos
  read_from_head true
  tag kubernetes.*
    @type multi_format
      format json
      time_key time
      time_type string
      time_format "%Y-%m-%dT%H:%M:%S.%NZ"
      keep_time_key false
      format regexp
      expression /^(?<time>.+) (?<stream>stdout|stderr)( (?<logtag>.))? (?<log>.*)$/
      time_format '%Y-%m-%dT%H:%M:%S.%N%:z'
      keep_time_key false

<filter kubernetes.var.log.containers.**.log>
  @type kubernetes_metadata

<match **>
  @type stdout

Environment variables for Kubernetes

If the name of the Kubernetes node the plugin is running on is set as an environment variable with the name K8S_NODE_NAME, it will reduce cache misses and needless calls to the Kubernetes API.

In the Kubernetes container definition, this is easily accomplished by:

- name: K8S_NODE_NAME
      fieldPath: spec.nodeName

Example input/output

Kubernetes creates symlinks to Docker log files in /var/log/containers/*.log. Docker logs in JSON format.

Assuming following inputs are coming from a log file named /var/log/containers/fabric8-console-controller-98rqc_default_fabric8-console-container-df14e0d5ae4c07284fa636d739c8fc2e6b52bc344658de7d3f08c36a2e804115.log:

  "log": "2015/05/05 19:54:41 \n",
  "stream": "stderr",
  "time": "2015-05-05T19:54:41.240447294Z"

Then output becomes as belows

  "log": "2015/05/05 19:54:41 \n",
  "stream": "stderr",
  "docker": {
    "id": "df14e0d5ae4c07284fa636d739c8fc2e6b52bc344658de7d3f08c36a2e804115",
  "kubernetes": {
    "host": "jimmi-redhat.localnet",
    "pod_id": "c76927af-f563-11e4-b32d-54ee7527188d",
    "pod_ip": "",
    "container_name": "fabric8-console-container",
    "namespace_name": "default",
    "namespace_id": "23437884-8e08-4d95-850b-e94378c9b2fd",
    "namespace_annotations": {
      "fabric8.io/git-commit": "5e1116f63df0bac2a80bdae2ebdc563577bbdf3c"
    "namespace_labels": {
      "product_version": "v1.0.0"
    "labels": {
      "component": "fabric8Console"


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Test it (GEM_HOME=vendor bundle install; GEM_HOME=vendor bundle exec rake test)
  5. Push to the branch (git push origin my-new-feature)
  6. Create new Pull Request

Copyright (c) 2015 jimmidyson