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076b8d4fba
Add OnReStartFailed which makes the health plugin stay up if the Corefile is corrupt and we revert to the previous version. Also needs a fix for the channel handling See #2659 Testing it will log the following when restarting with a corrupted Corefile ~~~ 2019-05-04T18:01:59.431Z [INFO] linux/amd64, go1.12.4, CoreDNS-1.5.0 linux/amd64, go1.12.4, [INFO] SIGUSR1: Reloading [INFO] Reloading [ERROR] Restart failed: Corefile:5 - Error during parsing: Unknown directive 'bdhfhdhj' [ERROR] SIGUSR1: starting with listener file descriptors: Corefile:5 - Error during parsing: Unknown directive 'bdhfhdhj' ~~~ After which the curl still works. This also needed a change to reset the channel used for the metrics go-routine which gets closed on shutdown, otherwise you'll see: ~~~ ^C[INFO] SIGINT: Shutting down panic: close of closed channel goroutine 90 [running]: github.com/coredns/coredns/plugin/health.(*health).OnFinalShutdown(0xc000089bc0, 0xc000063d88, 0x4afe6d) ~~~ Signed-off-by: Miek Gieben <miek@miek.nl>
79 lines
1.8 KiB
Markdown
79 lines
1.8 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 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, *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 endponts ":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* directive) then the following metric is exported:
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* `coredns_health_request_duration_seconds{}` - duration to process a HTTP query to the local
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`/health` endpoint. As this 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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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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