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Allow debug queries to etcd middleware (#150)

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With this you can retreive the raw data that the etcd middleware
used to create the reply. The debug data is put in TXT records
that are stuffed in the CH classs. This is only enabled if you
specify `debug` in the etcd stanza.

You can retrieve it by prefixing your query with 'o-o.debug.'
For instance:

; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost -p 1053 SRV o-o.debug.production.*.skydns.local
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47798
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 3

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;o-o.debug.production.*.skydns.local. IN	SRV

;; ANSWER SECTION:
production.*.skydns.local. 154	IN	SRV	10 50 8080 service1.example.com.
production.*.skydns.local. 154	IN	SRV	10 50 8080 service2.example.com.

;; ADDITIONAL SECTION:
skydns.local.skydns.east.production.rails.1. 154 CH TXT	"service1.example.com:8080(10,0,,false)[0,]"
skydns.local.skydns.west.production.rails.2. 154 CH TXT	"service2.example.com:8080(10,0,,false)[0,]"
This commit is contained in:
Miek Gieben
2016-05-22 21:16:26 +01:00
parent d35394a8df
commit c30671f4c0
9 changed files with 323 additions and 62 deletions
Download Patch File Download Diff File Expand all files Collapse all files

59
middleware/etcd/handler.go
View File

@@ -4,6 +4,7 @@ import (
"fmt"
"github.com/miekg/coredns/middleware"
"github.com/miekg/coredns/middleware/etcd/msg"
"github.com/miekg/dns"
"golang.org/x/net/context"
@@ -14,11 +15,18 @@ func (e Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
if state.QClass() != dns.ClassINET {
return dns.RcodeServerFailure, fmt.Errorf("can only deal with ClassINET")
}
name := state.Name()
if e.Debug {
if debug := isDebug(name); debug != "" {
e.debug = r.Question[0].Name
state.Clear()
state.Req.Question[0].Name = debug
}
}
// We need to check stubzones first, because we may get a request for a zone we
// are not auth. for *but* do have a stubzone forward for. If we do the stubzone
// handler will handle the request.
name := state.Name()
if e.Stubmap != nil && len(*e.Stubmap) > 0 {
for zone, _ := range *e.Stubmap {
if middleware.Name(zone).Matches(name) {
@@ -36,52 +44,62 @@ func (e Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
return e.Next.ServeDNS(ctx, w, r)
}
m := new(dns.Msg)
m.SetReply(r)
m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
var (
records, extra []dns.RR
debug []msg.Service
err error
)
switch state.Type() {
case "A":
records, err = e.A(zone, state, nil)
records, debug, err = e.A(zone, state, nil)
case "AAAA":
records, err = e.AAAA(zone, state, nil)
records, debug, err = e.AAAA(zone, state, nil)
case "TXT":
records, err = e.TXT(zone, state)
records, debug, err = e.TXT(zone, state)
case "CNAME":
records, err = e.CNAME(zone, state)
records, debug, err = e.CNAME(zone, state)
case "MX":
records, extra, err = e.MX(zone, state)
records, extra, debug, err = e.MX(zone, state)
case "SRV":
records, extra, err = e.SRV(zone, state)
records, extra, debug, err = e.SRV(zone, state)
case "SOA":
records = []dns.RR{e.SOA(zone, state)}
records, debug, err = e.SOA(zone, state)
case "NS":
if state.Name() == zone {
records, extra, err = e.NS(zone, state)
records, extra, debug, err = e.NS(zone, state)
break
}
fallthrough
default:
// Do a fake A lookup, so we can distinguish betwen NODATA and NXDOMAIN
_, err = e.A(zone, state, nil)
// Do a fake A lookup, so we can distinguish between NODATA and NXDOMAIN
_, debug, err = e.A(zone, state, nil)
}
if e.debug != "" {
// substitute this name with the original when we return the request.
state.Clear()
state.Req.Question[0].Name = e.debug
}
if isEtcdNameError(err) {
return e.Err(zone, dns.RcodeNameError, state)
return e.Err(zone, dns.RcodeNameError, state, debug)
}
if err != nil {
return dns.RcodeServerFailure, err
}
if len(records) == 0 {
return e.Err(zone, dns.RcodeSuccess, state)
return e.Err(zone, dns.RcodeSuccess, state, debug)
}
m := new(dns.Msg)
m.SetReply(r)
m.Authoritative, m.RecursionAvailable, m.Compress = true, true, true
m.Answer = append(m.Answer, records...)
m.Extra = append(m.Extra, extra...)
if e.debug != "" {
m.Extra = append(m.Extra, servicesToTxt(debug)...)
}
m = dedup(m)
state.SizeAndDo(m)
@@ -90,11 +108,12 @@ func (e Etcd) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
return dns.RcodeSuccess, nil
}
// NoData write a nodata response to the client.
func (e Etcd) Err(zone string, rcode int, state middleware.State) (int, error) {
// Err write an error response to the client.
func (e Etcd) Err(zone string, rcode int, state middleware.State, debug []msg.Service) (int, error) {
m := new(dns.Msg)
m.SetRcode(state.Req, rcode)
m.Ns = []dns.RR{e.SOA(zone, state)}
m.Ns, _, _ = e.SOA(zone, state)
m.Extra = servicesToTxt(debug)
state.SizeAndDo(m)
state.W.WriteMsg(m)
return rcode, nil