openapi: 3.1.0
info:
  title: CoreDNS Health API
  description: >-
    The CoreDNS health plugin exposes an HTTP health check endpoint at /health
    on port 8080 by default. It reports the overall health of the CoreDNS
    process and is used by Kubernetes liveness and readiness probes to determine
    if the DNS server is operational. When lameduck mode is enabled, the health
    endpoint returns HTTP 503 for a configurable duration before shutdown to
    allow graceful traffic draining.
  version: '2.x'
  contact:
    name: CoreDNS Community
    url: https://coredns.io/community/
  license:
    name: Apache 2.0
    url: https://www.apache.org/licenses/LICENSE-2.0
externalDocs:
  description: CoreDNS Health Plugin Documentation
  url: https://coredns.io/plugins/health/
servers:
  - url: http://localhost:8080
    description: CoreDNS Health HTTP server (default port, configurable)
tags:
  - name: Health
    description: >-
      Health check endpoints used by Kubernetes liveness and readiness probes
      to assess the operational state of the CoreDNS process.
  - name: Ready
    description: >-
      Readiness check endpoints that indicate whether CoreDNS plugins have
      finished initializing and are ready to serve DNS queries.
paths:
  /health:
    get:
      operationId: getHealth
      summary: CoreDNS liveness health check
      description: >-
        Returns the overall health status of the CoreDNS process. Returns HTTP
        200 with body "OK" when CoreDNS is alive and healthy. Returns HTTP 503
        during the lameduck shutdown period to signal that the instance is
        draining and should not receive new traffic. This endpoint is typically
        used as the Kubernetes liveness probe target.
      tags:
        - Health
      responses:
        '200':
          description: CoreDNS is healthy and alive.
          content:
            text/plain:
              schema:
                type: string
                example: OK
        '503':
          description: >-
            CoreDNS is in lameduck mode (shutting down gracefully). The process
            is still running but draining connections before exit.
          content:
            text/plain:
              schema:
                type: string
                example: lameduck
  /ready:
    get:
      operationId: getReadiness
      summary: CoreDNS readiness check
      description: >-
        Returns the readiness status of all CoreDNS plugins. Returns HTTP 200
        with body "OK" when all plugins that implement the Readiness interface
        report they are ready to serve traffic. Returns HTTP 503 if any plugin
        is not yet ready. This endpoint is typically used as the Kubernetes
        readiness probe target and requires the ready plugin to be enabled in
        the Corefile.
      tags:
        - Ready
      responses:
        '200':
          description: All CoreDNS plugins are ready to serve traffic.
          content:
            text/plain:
              schema:
                type: string
                example: OK
        '503':
          description: >-
            One or more CoreDNS plugins are not yet ready. The server is still
            initializing.
          content:
            text/plain:
              schema:
                type: string
                example: not ready