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k8s_event

Name

k8s_event - reports CoreDNS status to Kubernetes events.

Description

k8s_event listens for log printings, and reports them as Events to Kubernetes APIServer.

This plugin requires ...

  • the kubeapi plugin to create a connection to the Kubernetes API.
  • create/patch/update permission to the Events API.

Enabling this plugin is process-wide: enabling k8s_event in at least one server block enables it globally.

Syntax

k8s_event {
    level LEVELS...
    rate [QPS] [Burst] [CacheSize]
}
  • levels selects what level of logs should be reported as Kubernetes events. LEVELS is a space-separated list of log levels, supported levels are debug, error, fatal, info, and warning. The level of the log will be reflected on the Reason field of event, e.g. it will use CoreDNSWarning as Reason field for a warning log. If no level is specified, it defaults to error and warning.
  • rate is used to control the throttling of events.
    • QPS is the fill rate of the token bucket in queries per second, which is 1/300 by default.
    • Burst is the burst size used by the token bucket rate filtering, which is 25 by default.
    • CacheSize is the lru cache size used for event caching locally, which is 4096 by default.

External Plugin

To use this plugin, compile CoreDNS with this plugin added to the plugin.cfg. This plugin also requires the kubeapi plugin, which should be added to the end of plugin.cfg.

Deployment

By default, this plugin reports events on behalf of its own CoreDNS Pod, PodName and Namespace are collected through the Downward API.

When deploying CoreDNS in kubernetes, you should include the following environment variables.

env:
  - name: COREDNS_POD_NAME
    valueFrom:
      fieldRef:
        fieldPath: metadata.name
  - name: COREDNS_NAMESPACE
    valueFrom:
      fieldRef:
        fieldPath: metadata.namespace

When these environment variables are missing, this plugin reports events on behalf of the default namespace.

Also, the system:coredns ClusterRole should be appended with following.

- apiGroups:
  - events.k8s.io
  resources:
  - events
  verbs:
  - create
  - patch
  - update

Example

Listens for log printings of info, error, and warning levels, and reports them via in-cluster Kubernetes API. The event sending rate is controlled by QPS 0.15 token/sec, Burst 10 tokens, and LRUCacheSize 1024 tokens.

.:53 {
    kubeapi
    k8s_event {
      level info error warning
      rate 0.15 10 1024
    }
}

Outputs

$ kubectl get ev -A -w
NAMESPACE   LAST SEEN   TYPE      REASON           OBJECT              MESSAGE
default     1s          Normal    CoreDNSInfo      namespace/default   plugin/reload: Running configuration SHA512 = <omitted>
default     1s          Warning   CoreDNSError     namespace/default   plugin/errors: 2 <omitted>. A: read udp <omitted>: i/o timeout
default     1s          Warning   CoreDNSError     namespace/default   plugin/reload: Corefile changed but reload failed: <omitted>