Kubernetes

The Kubernetes Filter allows to enrich your log files with Kubernetes metadata.

When Fluent Bit is deployed in Kubernetes as a DaemonSet and configured to read the log files from the containers (using tail plugin), this filter aims to perform the following operations:

• Analyze the Tag and extract the following metadata:

  • POD Name

  • Namespace

  • Container Name

  • Container ID

• Query Kubernetes API Server to obtain extra metadata for the POD in question:

  • POD ID

  • Labels

  • Annotations

The data is cached locally in memory and appended to each record.

Configuration Parameters

The plugin supports the following configuration parameters:

Key	Description	Default
Buffer_Size	Set the buffer size for HTTP client when reading responses from Kubernetes API server. The value must be according to the Unit Size specification.	32k
Kube_URL	API Server end-point	https://kubernetes.default.svc.cluster.local:443
Kube_CA_File	CA certificate file	/var/run/secrets/kubernetes.io/serviceaccount/ca.crt
Kube_CA_Path	Absolute path to scan for certificate files
Kube_Token_File	Token file	/var/run/secrets/kubernetes.io/serviceaccount/token
Merge_Log	When enabled, it checks if the log field content is a JSON string map, if so, it append the map fields as part of the log structure.	Off
Merge_Log_Key	When Merge_Log is enabled, the filter tries to assume the log field from the incoming message is a JSON string message and make a structured representation of it at the same level of the log field in the map. Now if Merge_Log_Key is set (a string name), all the new structured fields taken from the original log content are inserted under the new key.
Merge_Log_Trim	When Merge_Log is enabled, trim (remove possible \n or \r) field values.	On
tls.debug	Debug level between 0 (nothing) and 4 (every detail).	-1
tls.verify	When enabled, turns on certificate validation when connecting to the Kubernetes API server.	On
Use_Journal	When enabled, the filter reads logs coming in Journald format.	Off
Regex_Parser	Set an alternative Parser to process record Tag and extract pod_name, namespace_name, container_name and docker_id. The parser must be registered in a parsers file (refer to parser filter-kube-test as an example).
K8S-Logging.Parser	Allow Kubernetes Pods to suggest a pre-defined Parser (read more about it in Kubernetes Annotations section)	Off
K8S-Logging.Exclude	Allow Kubernetes Pods to exclude their logs from the log processor (read more about it in Kubernetes Annotations section).	Off
Annotations	Include Kubernetes resource annotations in the extra metadata.	On
Kube_meta_preload_cache_dir	If set, Kubernetes meta-data can be cached/pre-loaded from files in JSON format in this directory, named as namespace-pod.meta
Dummy_Meta	If set, use dummy-meta data (for test/dev purposes)	Off

Kubernetes Annotations

A flexible feature of Fluent Bit Kubernetes filter is that allow Kubernetes Pods to suggest certain behaviors for the log processor pipeline when processing the records. At the moment it support:

• Suggest a pre-defined parser

• Request to exclude logs

The following annotations are available:

Annotation	Description	Default
fluentbit.io/parser[_stream][-container]	Suggest a pre-defined parser. The parser must be registered already by Fluent Bit. This option will only be processed if Fluent Bit configuration (Kubernetes Filter) have enabled the option K8S-Logging.Parser. If present, the stream (stdout or stderr) will restrict that specific stream. If present, the container can override a specific container in a Pod.
fluentbit.io/exclude	Request to Fluent Bit to exclude or not the logs generated by the Pod. This option will only be processed if Fluent Bit configuration (Kubernetes Filter) have enabled the option K8S-Logging.Exclude.	False

Annotation Examples in Pod definition

Suggest a parser

The following Pod definition runs a Pod that emits Apache logs to the standard output, in the Annotations it suggest that the data should be processed using the pre-defined parser called apache:

apiVersion: v1
kind: Pod
metadata:
  name: apache-logs
  labels:
    app: apache-logs
  annotations:
    fluentbit.io/parser: apache
spec:
  containers:
  - name: apache
    image: edsiper/apache_logs

Request to exclude logs

There are certain situations where the user would like to request that the log processor simply skip the logs from the Pod in question:

apiVersion: v1
kind: Pod
metadata:
  name: apache-logs
  labels:
    app: apache-logs
  annotations:
    fluentbit.io/exclude: "true"
spec:
  containers:
  - name: apache
    image: edsiper/apache_logs

Note that the annotation value is boolean which can take a true or false and must be quoted.