# Kubernetes Metadata Module (mmkubernetes)

Module Name: | mmkubernetes
Author: | Tomáš Heinrich Rich Megginson <rmeggins@redhat.com>

## Purpose

This module is used to add Kubernetes <https://kubernetes.io/> metadata to log messages logged by containers running in Kubernetes. It will add the namespace uuid, pod uuid, pod and namespace labels and annotations, and other metadata associated with the pod and namespace.

Note

This only works with log files in /var/log/containers/*.log (docker –log-driver=json-file, or CRI-O log files), or with journald entries with message properties CONTAINER_NAME and CONTAINER_ID_FULL (docker –log-driver=journald), and when the application running inside the container writes logs to stdout/stderr. This does not currently work with other log drivers.

For json-file and CRI-O logs, you must use the imfile module with the addmetadata=”on” parameter, and the filename must match the liblognorm rules specified by the filenamerules (filenamerules) or filenamerulebase (filenamerulebase) parameter values.

For journald logs, there must be a message property CONTAINER_NAME which matches the liblognorm rules specified by the containerrules (containerrules) or containerrulebase (containerrulebase) parameter values. The record must also have the message property CONTAINER_ID_FULL.

This module is implemented via the output module interface. This means that mmkubernetes should be called just like an action. After it has been called, there will be two new message properties: kubernetes and docker. There will be subfields of each one for the various metadata items: $!kubernetes!namespace_name $!kubernetes!labels!this-is-my-label, etc. There is currently only 1 docker subfield: $!docker!container_id. See https://github.com/ViaQ/elasticsearch-templates/blob/master/namespaces/kubernetes.yml and https://github.com/ViaQ/elasticsearch-templates/blob/master/namespaces/docker.yml for more details.

## Configuration Parameters

Note

Parameter names are case-insensitive; camelCase is recommended for readability.

### Action Parameters

Parameter | Summary
--- | ---
annotation_match | Selects pod or namespace annotations whose keys match given patterns.
allowunsignedcerts | Disables TLS peer certificate verification.
busyretryinterval | Sets the delay before retrying after a `429 Busy` response.
cacheentryttl | Sets the maximum age of entries in the metadata cache.
cacheexpireinterval | Controls how often to check for expired metadata cache entries.
containerrulebase | Specifies the rulebase file used to parse `CONTAINER_NAME` values.
containerrules | Defines lognorm rules to parse `CONTAINER_NAME` values for metadata.
de_dot | Replaces dots in annotation and label keys.
de_dot_separator | Defines the string used to replace dots when `de_dot` is enabled.
dstmetadatapath | Defines where the `kubernetes` and `docker` properties are written.
filenamerulebase | Specifies the rulebase file used to match json-file log filenames.
filenamerules | Defines lognorm rules to parse json-file log filenames for metadata.
KubernetesURL | Specifies the URL of the Kubernetes API server.
skipverifyhost | Skips verification of the Kubernetes API server hostname.
srcmetadatapath | Specifies the message property containing the original filename.
sslpartialchain | Enables OpenSSL `X509_V_FLAG_PARTIAL_CHAIN` verification.
tls.cacert | Specifies the CA certificate used to verify the Kubernetes API server.
tls.mycert | Specifies the client certificate for authenticating to Kubernetes.
tls.myprivkey | Specifies the unencrypted private key corresponding to `tls.mycert`.
token | Specifies the authentication token string.
tokenfile | Reads the authentication token from the specified file.

## Statistic Counter

This plugin maintains per-action statistics. The statistic is named “mmkubernetes($kubernetesurl)”, where $kubernetesurl is the KubernetesURL setting for the action.

Parameters are:

- recordseen - number of messages seen by the action which the action has determined have Kubernetes metadata associated with them

- namespacemetadatasuccess - the number of times a successful request was made to the Kubernetes API server for namespace metadata.

- namespacemetadatanotfound - the number of times a request to the Kubernetes API server for namespace metadata was returned with a 404 Not Found error code - the namespace did not exist at that time.

- namespacemetadatabusy - the number of times a request to the Kubernetes API server for namespace metadata was returned with a 429 Busy error code - the server was too busy to send a proper response.

- namespacemetadataerror - the number of times a request to the Kubernetes API server for namespace metadata was returned with some other error code not handled above. These are typically “hard” errors which require some sort of intervention to fix e.g. Kubernetes server down, credentials incorrect.

- podmetadatasuccess - the number of times a successful request was made to the Kubernetes API server for pod metadata.

- podmetadatanotfound - the number of times a request to the Kubernetes API server for pod metadata was returned with a 404 Not Found error code - the pod did not exist at that time.

- podmetadatabusy - the number of times a request to the Kubernetes API server for pod metadata was returned with a 429 Busy error code - the server was too busy to send a proper response.

- podmetadataerror - the number of times a request to the Kubernetes API server for pod metadata was returned with some other error code not handled above. These are typically “hard” errors which require some sort of intervention to fix e.g. Kubernetes server down, credentials incorrect.

- podcachenumentries - the number of entries in the pod metadata cache.

- namespacecachenumentries - the number of entries in the namespace metadata cache.

- podcachehits - the number of times a requested entry was found in the pod metadata cache.

- namespacecachehits - the number of times a requested entry was found in the namespace metadata cache.

- podcachemisses - the number of times a requested entry was not found in the pod metadata cache, and had to be requested from Kubernetes.

- namespacecachemisses - the number of times a requested entry was not found in the namespace metadata cache, and had to be requested from Kubernetes.

### Fields

These are the fields added from the metadata in the json-file filename, or from the CONTAINER_NAME and CONTAINER_ID_FULL fields from the imjournal input:

$!kubernetes!namespace_name, $!kubernetes!pod_name, $!kubernetes!container_name, $!docker!id, $!kubernetes!master_url.

If mmkubernetes can extract the above fields from the input, the following fields will always be present. If they are not present, mmkubernetes failed to look up the namespace or pod in Kubernetes:

$!kubernetes!namespace_id, $!kubernetes!pod_id, $!kubernetes!creation_timestamp, $!kubernetes!host

The following fields may be present, depending on how the namespace and pod are defined in Kubernetes, and depending on the value of the directive annotation_match:

$!kubernetes!labels, $!kubernetes!annotations, $!kubernetes!namespace_labels, $!kubernetes!namespace_annotations

More fields may be added in the future.

### Error Handling

If the plugin encounters a 404 Not Found in response to a request for namespace or pod metadata, that is, the pod or namespace is missing, the plugin will cache that result, and no metadata will be available for that pod or namespace forever. If the pod or namespace is recreated, you will need to restart rsyslog in order to clear the cache and allow it to find that metadata.

If the plugin gets a 429 Busy response, the plugin will _not_ cache that result, and will _not_ add the metadata to the record. This can happen in very large Kubernetes clusters when you run into the upper limit on the number of concurrent Kubernetes API service connections. You may have to increase that limit. In the meantime, you can control what the plugin does with those records using the busyretryinterval setting. If you want to continue to process the records, but with incomplete metadata, set busyretryinterval to a non-zero value, which will be the number of seconds after which mmkubernetes will retry the connection. The default value is 5, so by default, the plugin will retry the connection every 5 seconds. If the 429 error condition in the Kubernetes API server is brief and transient, this means you will have some (hopefully small) number of records without the metadata such as the uuids, labels, and annotations, but your pipeline will not stop. If the 429 error condition in the Kubernetes API server is persistent, it may require Kubernetes API server administrator intervention to address, and you may want to use the busyretryinterval value of “0”. This will cause the module to return a “hard” error (see below).

For other errors, the plugin will assume they are “hard” errors requiring admin intervention, return an error code, and rsyslog will suspend the plugin. Use the Statistic Counter to monitor for problems getting data from the Kubernetes API service.

### Example

Assuming you have an imfile input reading from docker json-file container logs managed by Kubernetes, with addmetadata=”on” so that mmkubernetes can get the basic necessary Kubernetes metadata from the filename:

    input(type="imfile" file="/var/log/containers/*.log"
          tag="kubernetes" addmetadata="on")

(Add reopenOnTruncate=”on” if using Docker, not required by CRI-O).

and/or an imjournal input for docker journald container logs annotated by Kubernetes:

    input(type="imjournal")

Then mmkubernetes can be used to annotate log records like this:

    module(load="mmkubernetes")

    action(type="mmkubernetes")

After this, you should have log records with fields described in the Fields section above.

### Credits

This work is based on https://github.com/fabric8io/fluent-plugin-kubernetes_metadata_filter and has many of the same features.

Support: rsyslog Assistant | GitHub Discussions | GitHub Issues: rsyslog source project

Contributing: Source & docs: rsyslog source project

© 2008–2025 Rainer Gerhards and others. Licensed under the Apache License 2.0.