health

health enables a health check endpoint.

Description

By enabling health any plugin that implements it will be queried for it’s health. The combined health is exported, by default, on port 8080/health .

Syntax

health [ADDRESS]

Optionally takes an address; the default is :8080. The health path is fixed to /health. The health endpoint returns a 200 response code and the word “OK” when CoreDNS is healthy. It returns a 503. health periodically (1s) polls plugin that exports health information. If any of the plugin signals that it is unhealthy, the server will go unhealthy too. Each plugin that supports health checks has a section “Health” in their README.

More options can be set with this extended syntax:

health [ADDRESS] {
    lameduck DURATION
}
  • Where lameduck will make the process unhealthy then wait for DURATION before the process shuts down.

Plugins

Any plugin that implements the Healther interface will be used to report health.

Metrics

If monitoring is enabled (via the prometheus directive) then the following metric is exported:

  • coredns_health_request_duration_seconds{} - duration to process a /health query. As this should be a local operation it should be fast. A (large) increases in this duration indicates the CoreDNS process is having trouble keeping up.

Examples

Run another health endpoint on http://localhost:8091.

. {
    health localhost:8091
}

Set a lameduck duration of 1 second:

. {
    health localhost:8091 {
        lameduck 1s
    }
}