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fix(metrics): preserve request size from plugins (#7313)

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The rewrite plugin modifies DNS messages, affecting the request
size observed in the coredns_dns_request_size_bytes metric.

This change captures the original request size before any plugins
can modify it. It adds a functional options pattern to Report() to
pass this information while maintaining API compatibility.

Tests have been added to verify the fix prevents rewrite from
affecting the request size metrics.

Docs included.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
This commit is contained in:
Ville Vesilehto
2025-05-22 16:38:22 +03:00
committed by GitHub
parent 528cc26a4c
commit 32ea433a29
7 changed files with 337 additions and 15 deletions
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7
plugin/metrics/handler.go
View File

@@ -16,6 +16,9 @@ import (
func (m *Metrics) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
state := request.Request{W: w, Req: r}
// Capture the original request size before any plugins modify it
originalSize := r.Len()
qname := state.QName()
zone := plugin.Zones(m.ZoneNames()).Matches(qname)
if zone == "" {
@@ -34,7 +37,9 @@ func (m *Metrics) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
rc = status
}
plugin := m.authoritativePlugin(rw.Caller)
vars.Report(WithServer(ctx), state, zone, WithView(ctx), rcode.ToString(rc), plugin, rw.Len, rw.Start)
// Pass the original request size to vars.Report
vars.Report(WithServer(ctx), state, zone, WithView(ctx), rcode.ToString(rc), plugin,
rw.Len, rw.Start, vars.WithOriginalReqSize(originalSize))
return status, err
}