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* 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
96 lines
2.3 KiB
Markdown
96 lines
2.3 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
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[healt.Healther interface](https://godoc.org/github.com/coredns/coredns/plugin/health#Healther)
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will be queried for it's health. The combined 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 this server is healthy. It returns
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a 503. *health* periodically (1s) polls plugins that exports health information. If any of the
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plugins signals that it is unhealthy, the server will go unhealthy too. Each plugin that supports
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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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If you have multiple Server Blocks and need to export health for each of the plugins, you must run
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health endpoints on different ports:
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~~~ corefile
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com {
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whoami
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health :8080
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}
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net {
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erratic
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health :8081
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}
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~~~
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Note that if you format this in one server block you will get an error on startup, that the second
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server can't setup the health plugin (on the same port).
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~~~ txt
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com net {
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whoami
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erratic
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health :8080
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}
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~~~~
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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 with its query load.
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Note that this metric *does not* have a `server` label, because being overloaded is a symptom of
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the running process, *not* a specific server.
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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:8092 {
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lameduck 1s
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}
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}
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~~~
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