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Metrics (#1579)

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* plugin/metrics: set server address in context

Allow cross server block metrics to co-exist; for this we should label
each metric with the server label. Put this information in the context
and provide a helper function to get it out.

Abstracting with entirely away with difficult as the release client_go
(0.8.0) doesn't have the CurryWith functions yet. So current use is like
so:

define metric, with server label:

	RcodeCount = prometheus.NewCounterVec(prometheus.CounterOpts{
		Namespace: plugin.Namespace,
		Subsystem: "forward",
		Name:      "response_rcode_count_total",
		Help:      "Counter of requests made per upstream.",
	}, []string{"server", "rcode", "to"})

And report ith with the helper function metrics.WithServer:

	RcodeCount.WithLabelValues(metrics.WithServer(ctx), rc, p.addr).Add(1)
This commit is contained in:
Miek Gieben 2018-04-01 13:57:03 +01:00 • committed by GitHub
parent 5c5a98ee29
commit 4df416ca1d
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4 changed files with 43 additions and 7 deletions
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24
plugin/metrics/context.go Normal file
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package metrics
import (
"github.com/coredns/coredns/plugin"
"golang.org/x/net/context"
)
// WithServer returns the current server handling the request. It returns the
// server listening address: <scheme>://[<bind>]:<port> Normally this is
// something like "dns://:53", but if the bind plugin is used, i.e. "bind
// 127.0.0.53", it will be "dns://127.0.0.53:53", etc. If not address is found
// the empty string is returned.
//
// Basic usage with a metric:
//
// <metric>.WithLabelValues(metrics.WithServer(ctx), labels..).Add(1)
func WithServer(ctx context.Context) string {
srv := ctx.Value(plugin.ServerCtx{})
if srv == nil {
return ""
}
return srv.(string)
}