Don't double report metrics on error

When there is an error use a different function to report the metrics, in case the plugin chain handled the request the metrics are already reported. Builds up on #2716 Fixes: #2717 Signed-off-by: Miek Gieben <miek@miek.nl>
coredns · Mar 24, 2019 · dc32dcf · dc32dcf
1 parent e9b9a91
commit dc32dcf
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Showing 2 changed files with 14 additions and 5 deletions.
diff --git a/core/dnsserver/server.go b/core/dnsserver/server.go
@@ -205,7 +205,7 @@ func (s *Server) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 	// The default dns.Mux checks the question section size, but we have our
 	// own mux here. Check if we have a question section. If not drop them here.
 	if r == nil || len(r.Question) == 0 {
-		errorFunc(ctx, w, r, dns.RcodeServerFailure)
+		errorAndMetricsFunc(ctx, w, r, dns.RcodeServerFailure)
 		return
 	}
 
@@ -215,13 +215,13 @@ func (s *Server) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 			// need to make sure that we stay alive up here
 			if rec := recover(); rec != nil {
 				vars.Panic.Inc()
-				errorFunc(ctx, w, r, dns.RcodeServerFailure)
+				errorAndMetricsFunc(ctx, w, r, dns.RcodeServerFailure)
 			}
 		}()
 	}
 
 	if !s.classChaos && r.Question[0].Qclass != dns.ClassINET {
-		errorFunc(ctx, w, r, dns.RcodeRefused)
+		errorAndMetricsFunc(ctx, w, r, dns.RcodeRefused)
 		return
 	}
 
@@ -310,7 +310,7 @@ func (s *Server) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 	}
 
 	// Still here? Error out with REFUSED.
-	errorFunc(ctx, w, r, dns.RcodeRefused)
+	errorAndMetricsFunc(ctx, w, r, dns.RcodeRefused)
 }
 
 // OnStartupComplete lists the sites served by this server
@@ -338,6 +338,13 @@ func (s *Server) Tracer() ot.Tracer {
 
 // errorFunc responds to an DNS request with an error.
 func errorFunc(ctx context.Context, w dns.ResponseWriter, r *dns.Msg, rc int) {
+	answer := new(dns.Msg)
+	answer.SetRcode(r, rc)
+	state.SizeAndDo(answer)
+	w.WriteMsg(answer)
+}
+
+func errorAndMetricsFunc(ctx context.Context, w dns.ResponseWriter, r *dns.Msg, rc int) {
 	state := request.Request{W: w, Req: r}
 
 	answer := new(dns.Msg)

diff --git a/plugin/metrics/vars/report.go b/plugin/metrics/vars/report.go
@@ -10,7 +10,9 @@ import (
 	"github.com/miekg/dns"
 )
 
-// Report reports the metrics data associated with request.
+// Report reports the metrics data associated with request. This function is exported because it is also
+// called from core/dnsserver to report requests hitting the server that should not be handled and are thus
+// not sent down the plugin chain.
 func Report(ctx context.Context, req request.Request, zone, rcode string, size int, start time.Time) {
 	// Proto and Family.
 	net := req.Proto()