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Reduce the cardinality of health endpoint metrics (#4650)

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The health endpoint histogram has a large amount of cardinality for a
simple endpoint. Introduce a new "Slim" set of buckets for `/health` to
reduce the metrics load on large deployments. Especially those that have
per-node DNS caching services.

Add a metric to count internal health check failures rather than use the
timeout value as side effect monitor of the check error. This avoids
incorrectly recording the timeout value if there is an error that is not
a timeout (ex. refused)

Signed-off-by: SuperQ <superq@gmail.com>
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Ben Kochie 2021-05-27 15:16:38 +02:00 • committed by GitHub
parent 4c0fdc3909
commit 9edfaed631
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3 changed files with 17 additions and 4 deletions
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plugin/plugin.go
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@ -105,5 +105,8 @@ const Namespace = "coredns"
// TimeBuckets is based on Prometheus client_golang prometheus.DefBuckets
var TimeBuckets = prometheus.ExponentialBuckets(0.00025, 2, 16) // from 0.25ms to 8 seconds
// SlimTimeBuckets is low cardinality set of duration buckets.
var SlimTimeBuckets = prometheus.ExponentialBuckets(0.00025, 10, 5) // from 0.25ms to 2.5 seconds
// ErrOnce is returned when a plugin doesn't support multiple setups per server.
var ErrOnce = errors.New("this plugin can only be used once per Server Block")