4c7ae4ea95
* plugin/health: update README Make more clear in the readme that health is limited to 1 server. Fixes #1722 * rephrase and remove ~~~ corefile because it will fail
health
Name
health - enables a health check endpoint.
Description
By enabling health any plugin that implements healt.Healther interface 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 this server is healthy. It returns
a 503. health periodically (1s) polls plugins that exports health information. If any of the
plugins 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.
If you have multiple Server Blocks and need to export health for each of the plugins, you must run health endpoints on different ports:
com {
whoami
health :8080
}
net {
erratic
health :8081
}
Note that if you format this in one server block you will get an error on startup, that the second server can't setup the health plugin (on the same port).
com net {
whoami
erratic
health :8080
}
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 with its query load.
Note that this metric does not have a server label, because being overloaded is a symptom of
the running process, not a specific server.
Examples
Run another health endpoint on http://localhost:8091.
. {
health localhost:8091
}
Set a lameduck duration of 1 second:
. {
health localhost:8092 {
lameduck 1s
}
}