c39e5cd014
* plugin/health: add lameduck mode Add a way to configure lameduck more, i.e. set health to false, stop polling plugins. Then wait for a duration before shutting down. As the health middleware is configured early on in the plugin list, it will hold up all other shutdown, meaning we still answer queries. * Add New * More tests * golint * remove confusing text
health
Name
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
lameduckwill 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
}
}