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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
66 lines
1.6 KiB
Markdown
66 lines
1.6 KiB
Markdown
# health
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## Name
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*health* - enables a health check endpoint.
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## Description
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By enabling *health* any plugin that implements it will be queried for it's health. The combined
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health is exported, by default, on port 8080/health .
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## Syntax
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~~~
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health [ADDRESS]
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~~~
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Optionally takes an address; the default is `:8080`. The health path is fixed to `/health`. The
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health endpoint returns a 200 response code and the word "OK" when CoreDNS is healthy. It returns
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a 503. *health* periodically (1s) polls plugin that exports health information. If any of the
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plugin signals that it is unhealthy, the server will go unhealthy too. Each plugin that
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supports health checks has a section "Health" in their README.
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More options can be set with this extended syntax:
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~~~
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health [ADDRESS] {
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lameduck DURATION
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}
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~~~
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* Where `lameduck` will make the process unhealthy then *wait* for **DURATION** before the process
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shuts down.
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## Plugins
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Any plugin that implements the Healther interface will be used to report health.
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## Metrics
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If monitoring is enabled (via the *prometheus* directive) then the following metric is exported:
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* `coredns_health_request_duration_seconds{}` - duration to process a /health query. As this should
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be a local operation it should be fast. A (large) increases in this duration indicates the
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CoreDNS process is having trouble keeping up.
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## Examples
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Run another health endpoint on http://localhost:8091.
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~~~ corefile
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. {
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health localhost:8091
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}
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~~~
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Set a lameduck duration of 1 second:
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~~~ corefile
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. {
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health localhost:8091 {
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lameduck 1s
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}
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}
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~~~
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