Update kubernetes filter documentation with the usage of Owner_References. (#1577)

Signed-off-by: shuaichen <[email protected]>

Author: shuaich

pipeline/filters/kubernetes.md

@@ -9,9 +9,10 @@ When Fluent Bit is deployed in Kubernetes as a DaemonSet and configured to read
   * Namespace
   * Container Name
   * Container ID
-* Query Kubernetes API Server to obtain extra metadata for the POD in question:
+* Query Kubernetes API Server or Kubelet to obtain extra metadata for the POD in question:
   * Pod ID
   * Labels
+  * Owner References
   * Annotations
   * Namespace Labels
   * Namespace Annotations
@@ -59,6 +60,7 @@ The plugin supports the following configuration parameters:
 | Namespace\_Labels | Include Kubernetes namespace resource labels in the extra metadata. See [Kubernetes Namespace Meta](#kubernetes-namespace-meta)| Off |
 | Namespace\_Annotations | Include Kubernetes namespace resource annotations in the extra metadata. See [Kubernetes Namespace Meta](#kubernetes-namespace-meta)| Off |
 | Namespace\_Metadata\_Only | Include Kubernetes namespace metadata only and no pod metadata. If this is set, the values of `Labels` and `Annotations` are ignored. See [Kubernetes Namespace Meta](#kubernetes-namespace-meta)| Off |
+| Owner\_References | Include Kubernetes owner references in the extra metadata | Off |
 
 ## Processing the 'log' value
 
@@ -156,6 +158,14 @@ spec:
 
 Note that the annotation value is boolean which can take a _true_ or _false_ and **must** be quoted.
 
+## Kubernetes Owner References
+
+An opt-in feature of Fluent Bit Kubernetes filter to include owner references information under `kubernetes.ownerReferences` field in the record when enabled. An example of record is shown below.
+
+```
+"kubernetes"=>{"pod_name"=>"fluentbit-gke-2p6b5", "namespace_name"=>"kube-system", "pod_id"=>"c759a5f5-xxxx-xxxx-9117-8a1dc0b1f907", "labels"=>{"component"=>"xxxx", "controller-revision-hash"=>"77665fff9", "k8s-app"=>"fluentbit-xxxx"}, "ownerReferences"=>[{"apiVersion"=>"apps/v1", "kind"=>"DaemonSet", "name"=>"fluentbit-gke", "uid"=>"1a12c3e2-d6c4-4a8a-b877-dd3c857d1aea", "controller"=>true, "blockOwnerDeletion"=>true}], "host"=>"xxx-2a9c049c-qgw3", "pod_ip"=>"10.128.0.111", "container_name"=>"fluentbit", "docker_id"=>"2accxxx", "container_hash"=>"xxxx", "container_image"=>"sha256:5163dxxxxea2"}}
+```
+
 ## Workflow of Tail + Kubernetes Filter
 
 Kubernetes Filter depends on either [Tail](../inputs/tail.md) or [Systemd](../inputs/systemd.md) input plugins to process and enrich records with Kubernetes metadata. Here we will explain the workflow of Tail and how it configuration is correlated with Kubernetes filter. Consider the following configuration example \(just for demo purposes, not production\):