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* add detail to docs; bypass proxy in self health check Signed-off-by: Chris O'Haver <cohaver@infoblox.com>
81 lines
2.1 KiB
Markdown
81 lines
2.1 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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Enabled process wide health endpoint. When CoreDNS is up and running this returns a 200 OK HTTP
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status code. The 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.
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An extra option 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 delay shutdown for **DURATION**. /health will still answer 200 OK.
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Note: The *ready* plugin will not answer OK while CoreDNS is in lame duck mode prior to shutdown.
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If you have multiple Server Blocks, *health* can only be enabled in one of them (as it is process
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wide). If you really need multiple endpoints, you must run 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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Doing this is supported but both endpoints ":8080" and ":8081" will export the exact same health.
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## Metrics
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If monitoring is enabled (via the *prometheus* plugin) then the following metrics are exported:
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* `coredns_health_request_duration_seconds{}` - The *health* plugin performs a self health check
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once per second on the `/health` endpoint. This metric is the duration to process that request.
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As this is a local operation it should be fast. A (large) increase in this
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duration indicates the CoreDNS process is having trouble keeping up with its query load.
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* `coredns_health_request_failures_total{}` - The number of times the self health check failed.
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Note that these metrics *do 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 lame duck 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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