Simple patch to add extra TRACE level logging for failed requests

consul-dns-log.patch

diff --git a/command/agent/dns.go b/command/agent/dns.go
index 7f373cd4..9fa78b66 100644
--- a/command/agent/dns.go
+++ b/command/agent/dns.go
@@ -270,6 +270,9 @@ func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
        if err := resp.WriteMsg(m); err != nil {
                d.logger.Printf("[WARN] dns: failed to respond: %v", err)
        }
+       if m.MsgHdr.Rcode != 0 {
+               d.logger.Printf("[TRACE] dns: request for %v failed: rcode=%s", q, dns.RcodeToString[m.MsgHdr.Rcode])
+       }
 }

 // addSOA is used to add an SOA record to a message for the given domain
@@ -939,6 +942,9 @@ func (d *DNSServer) handleRecurse(resp dns.ResponseWriter, req *dns.Msg) {
                        if err := resp.WriteMsg(r); err != nil {
                                d.logger.Printf("[WARN] dns: failed to respond: %v", err)
                        }
+                       if r.MsgHdr.Rcode != 0 {
+                               d.logger.Printf("[TRACE] dns: request for %v failed: rcode=%s", q, dns.RcodeToString[r.MsgHdr.Rcode])
+                       }
                        return
                }
                d.logger.Printf("[ERR] dns: recurse failed: %v", err)