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Metrics: expand coredns_dns_responses_total with plugin label (#4914)

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* Metrics: expand coredns_dns_responses_total with plugin label

This adds (somewhat hacky?) code to add a plugin label to the
coredns_dns_responses_total metric. It's completely obvlious to the
plugin as we just check who called the *recorder.WriteMsg method. We use
runtime.Caller( 1 2 3) to get multiple levels of callers, this should be
deep enough, but it depends on the dns.ResponseWriter wrapping that's
occuring.

README.md of metrics updates and test added in test/metrics_test.go to
check for the label being set.

I went through the plugin to see what metrics could be removed, but
actually didn't find any, the plugin push out metrics that make sense.

Due to the path fiddling to figure out the plugin name I doubt this
works (out-of-the-box) for external plugins, but I haven't tested that.

Signed-off-by: Miek Gieben <miek@miek.nl>

* better comment

Signed-off-by: Miek Gieben <miek@miek.nl>

* Metrics: expand coredns_dns_responses_total with plugin label

This adds (somewhat hacky?) code to add a plugin label to the
coredns_dns_responses_total metric. It's completely obvlious to the
plugin as we just check who called the *recorder.WriteMsg method. We use
runtime.Caller( 1 2 3) to get multiple levels of callers, this should be
deep enough, but it depends on the dns.ResponseWriter wrapping that's
occuring.

README.md of metrics updates and test added in test/metrics_test.go to
check for the label being set.

I went through the plugin to see what metrics could be removed, but
actually didn't find any, the plugin push out metrics that make sense.

Due to the path fiddling to figure out the plugin name I doubt this
works (out-of-the-box) for external plugins, but I haven't tested that.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Update core/dnsserver/server.go

Co-authored-by: dilyevsky <ilyevsky@gmail.com>

* Use [3]string

Signed-off-by: Miek Gieben <miek@miek.nl>

* imports

Signed-off-by: Miek Gieben <miek@miek.nl>

* remove dnstest changes

Signed-off-by: Miek Gieben <miek@miek.nl>

* revert

Signed-off-by: Miek Gieben <miek@miek.nl>

* Add some sleeps to make it less flaky

Signed-off-by: Miek Gieben <miek@miek.nl>

* Revert "Add some sleeps to make it less flaky"

This reverts commit b5c6655196.

* Remove forward when not needed

Signed-off-by: Miek Gieben <miek@miek.nl>

* remove newline

Signed-off-by: Miek Gieben <miek@miek.nl>

Co-authored-by: dilyevsky <ilyevsky@gmail.com>
This commit is contained in:
Miek Gieben 2021-11-12 16:07:05 +00:00 • committed by GitHub
parent 29cae57932
commit 6953ab2b4f
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GPG key ID: 4AEE18F83AFDEB23
8 changed files with 85 additions and 20 deletions
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21
plugin/metrics/handler.go
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@ -2,10 +2,10 @@ package metrics
import (
"context"
"path/filepath"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/metrics/vars"
"github.com/coredns/coredns/plugin/pkg/dnstest"
"github.com/coredns/coredns/plugin/pkg/rcode"
"github.com/coredns/coredns/request"
@ -23,7 +23,7 @@ func (m *Metrics) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
}
// Record response to get status code and size of the reply.
rw := dnstest.NewRecorder(w)
rw := NewRecorder(w)
status, err := plugin.NextOrFailure(m.Name(), m.Next, ctx, rw, r)
rc := rw.Rcode
@ -33,10 +33,25 @@ func (m *Metrics) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
// see https://github.com/coredns/coredns/blob/master/core/dnsserver/server.go#L318
rc = status
}
vars.Report(WithServer(ctx), state, zone, rcode.ToString(rc), rw.Len, rw.Start)
plugin := m.authoritativePlugin(rw.Caller)
vars.Report(WithServer(ctx), state, zone, rcode.ToString(rc), plugin, rw.Len, rw.Start)
return status, err
}
// Name implements the Handler interface.
func (m *Metrics) Name() string { return "prometheus" }
// authoritativePlugin returns which of made the write, if none is found the empty string is returned.
func (m *Metrics) authoritativePlugin(caller [3]string) string {
// a b and c contain the full path of the caller, the plugin name 2nd last elements
// .../coredns/plugin/whoami/whoami.go --> whoami
// this is likely FS specific, so use filepath.
for _, c := range caller {
plug := filepath.Base(filepath.Dir(c))
if _, ok := m.plugins[plug]; ok {
return plug
}
}
return ""
}