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992d4c20db
* perf(loadbalance): fast-path zero-allocation roundRobin for homogeneous record sets Signed-off-by: Manuel Rüger <manuel@rueg.eu> * plugin/loadbalance: copy before shuffling in the fast path The fast path shuffled the caller's slice in place, which is not safe. roundRobin must not modify its input: a backend may hand back a slice it owns rather than one built for the response. plugin/file does exactly that - Lookup returns elem.Type(qtype), which is the zone tree's own []dns.RR - so an in-place shuffle reorders the zone itself, visible to every other query and racing with the ones running concurrently. Copy the records into a fresh slice and shuffle that instead. This is still a single allocation rather than the four slices the partitioning path builds, so most of the gain is kept: name old time/op new time/op delta RoundRobin 353 ns 244 ns -31% name old alloc/op new alloc/op delta RoundRobin 118 B 54 B -54% name old allocs/op new allocs/op delta RoundRobin 5 4 -20% Also reorder the type check so a response led by a CNAME is rejected on the first record instead of scanning the whole answer section first. TestRoundRobinDoesNotMutateInput pins the contract; it fails against the in-place version. Signed-off-by: Manuel Rüger <manuel@rueg.eu> --------- Signed-off-by: Manuel Rüger <manuel@rueg.eu>
257 lines
8.3 KiB
Go
257 lines
8.3 KiB
Go
package loadbalance
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import (
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"context"
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"testing"
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"github.com/coredns/coredns/plugin"
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"github.com/coredns/coredns/plugin/pkg/dnstest"
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"github.com/coredns/coredns/plugin/test"
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"github.com/miekg/dns"
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)
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func TestLoadBalanceRandom(t *testing.T) {
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rm := LoadBalance{Next: handler(), shuffle: randomShuffle}
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// the first X records must be cnames after this test
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tests := []struct {
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answer []dns.RR
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extra []dns.RR
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cnameAnswer int
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cnameExtra int
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addressAnswer int
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addressExtra int
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mxAnswer int
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mxExtra int
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}{
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{
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answer: []dns.RR{
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test.CNAME("cname1.region2.skydns.test. 300 IN CNAME cname2.region2.skydns.test."),
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test.CNAME("cname2.region2.skydns.test. 300 IN CNAME cname3.region2.skydns.test."),
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test.CNAME("cname5.region2.skydns.test. 300 IN CNAME cname6.region2.skydns.test."),
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test.CNAME("cname6.region2.skydns.test. 300 IN CNAME endpoint.region2.skydns.test."),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.1"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx1.region2.skydns.test."),
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test.MX("mx.region2.skydns.test. 300 IN MX 2 mx2.region2.skydns.test."),
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test.MX("mx.region2.skydns.test. 300 IN MX 3 mx3.region2.skydns.test."),
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},
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cnameAnswer: 4,
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addressAnswer: 1,
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mxAnswer: 3,
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},
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{
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answer: []dns.RR{
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.1"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx1.region2.skydns.test."),
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test.CNAME("cname.region2.skydns.test. 300 IN CNAME endpoint.region2.skydns.test."),
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},
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cnameAnswer: 1,
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addressAnswer: 1,
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mxAnswer: 1,
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},
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{
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answer: []dns.RR{
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx1.region2.skydns.test."),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.1"),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.2"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx2.region2.skydns.test."),
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test.CNAME("cname2.region2.skydns.test. 300 IN CNAME cname3.region2.skydns.test."),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.3"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx3.region2.skydns.test."),
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},
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extra: []dns.RR{
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.1"),
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test.AAAA("endpoint.region2.skydns.test. 300 IN AAAA ::1"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx1.region2.skydns.test."),
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test.CNAME("cname2.region2.skydns.test. 300 IN CNAME cname3.region2.skydns.test."),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx2.region2.skydns.test."),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.3"),
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test.AAAA("endpoint.region2.skydns.test. 300 IN AAAA ::2"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx3.region2.skydns.test."),
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},
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cnameAnswer: 1,
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cnameExtra: 1,
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addressAnswer: 3,
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addressExtra: 4,
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mxAnswer: 3,
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mxExtra: 3,
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},
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}
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rec := dnstest.NewRecorder(&test.ResponseWriter{})
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for i, test := range tests {
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req := new(dns.Msg)
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req.SetQuestion("region2.skydns.test.", dns.TypeSRV)
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req.Answer = test.answer
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req.Extra = test.extra
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_, err := rm.ServeDNS(context.TODO(), rec, req)
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if err != nil {
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t.Errorf("Test %d: Expected no error, but got %s", i, err)
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continue
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}
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cname, address, mx, sorted := countRecords(rec.Msg.Answer)
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if !sorted {
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t.Errorf("Test %d: Expected CNAMEs, then AAAAs, then MX in Answer, but got mixed", i)
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}
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if cname != test.cnameAnswer {
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t.Errorf("Test %d: Expected %d CNAMEs in Answer, but got %d", i, test.cnameAnswer, cname)
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}
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if address != test.addressAnswer {
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t.Errorf("Test %d: Expected %d A/AAAAs in Answer, but got %d", i, test.addressAnswer, address)
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}
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if mx != test.mxAnswer {
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t.Errorf("Test %d: Expected %d MXs in Answer, but got %d", i, test.mxAnswer, mx)
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}
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cname, address, mx, sorted = countRecords(rec.Msg.Extra)
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if !sorted {
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t.Errorf("Test %d: Expected CNAMEs, then AAAAs, then MX in Extra, but got mixed", i)
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}
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if cname != test.cnameExtra {
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t.Errorf("Test %d: Expected %d CNAMEs in Extra, but got %d", i, test.cnameAnswer, cname)
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}
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if address != test.addressExtra {
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t.Errorf("Test %d: Expected %d A/AAAAs in Extra, but got %d", i, test.addressAnswer, address)
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}
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if mx != test.mxExtra {
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t.Errorf("Test %d: Expected %d MXs in Extra, but got %d", i, test.mxAnswer, mx)
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}
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}
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}
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func TestLoadBalanceXFR(t *testing.T) {
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rm := LoadBalance{Next: handler()}
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answer := []dns.RR{
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test.SOA("skydns.test. 30 IN SOA ns.dns.skydns.test. hostmaster.skydns.test. 1542756695 7200 1800 86400 30"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx1.region2.skydns.test."),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.1"),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.2"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx2.region2.skydns.test."),
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test.CNAME("cname2.region2.skydns.test. 300 IN CNAME cname3.region2.skydns.test."),
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test.A("endpoint.region2.skydns.test. 300 IN A 10.240.0.3"),
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test.MX("mx.region2.skydns.test. 300 IN MX 1 mx3.region2.skydns.test."),
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test.SOA("skydns.test. 30 IN SOA ns.dns.skydns.test. hostmaster.skydns.test. 1542756695 7200 1800 86400 30"),
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}
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for _, xfrtype := range []uint16{dns.TypeIXFR, dns.TypeAXFR} {
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rec := dnstest.NewRecorder(&test.ResponseWriter{})
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req := new(dns.Msg)
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req.SetQuestion("skydns.test.", xfrtype)
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req.Answer = answer
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_, err := rm.ServeDNS(context.TODO(), rec, req)
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if err != nil {
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t.Errorf("Expected no error, but got %s for %s", err, dns.TypeToString[xfrtype])
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continue
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}
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if rec.Msg.Answer[0].Header().Rrtype != dns.TypeSOA {
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t.Errorf("Expected SOA record for first answer for %s", dns.TypeToString[xfrtype])
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}
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if rec.Msg.Answer[len(rec.Msg.Answer)-1].Header().Rrtype != dns.TypeSOA {
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t.Errorf("Expected SOA record for last answer for %s", dns.TypeToString[xfrtype])
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}
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}
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}
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func countRecords(result []dns.RR) (cname int, address int, mx int, sorted bool) {
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const (
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Start = iota
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CNAMERecords
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ARecords
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MXRecords
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Any
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)
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// The order of the records is used to determine if the round-robin actually did anything.
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sorted = true
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cname = 0
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address = 0
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mx = 0
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state := Start
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for _, r := range result {
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switch r.Header().Rrtype {
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case dns.TypeCNAME:
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sorted = sorted && state <= CNAMERecords
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state = CNAMERecords
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cname++
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case dns.TypeA, dns.TypeAAAA:
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sorted = sorted && state <= ARecords
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state = ARecords
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address++
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case dns.TypeMX:
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sorted = sorted && state <= MXRecords
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state = MXRecords
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mx++
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default:
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state = Any
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}
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}
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return cname, address, mx, sorted
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}
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func handler() plugin.Handler {
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return plugin.HandlerFunc(func(_ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
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w.WriteMsg(r)
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return dns.RcodeSuccess, nil
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})
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}
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func BenchmarkRoundRobin(b *testing.B) {
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answer := []dns.RR{
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test.A("a.example.org. 300 IN A 10.0.0.1"),
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test.A("a.example.org. 300 IN A 10.0.0.2"),
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test.A("a.example.org. 300 IN A 10.0.0.3"),
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}
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b.ReportAllocs()
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for b.Loop() {
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_ = roundRobin(answer)
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}
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}
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// TestRoundRobinDoesNotMutateInput guards the contract that roundRobin leaves its
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// input alone. Backends may return a slice they own - plugin/file answers directly
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// out of the zone tree - so shuffling in place would corrupt shared state and race
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// with concurrent queries.
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func TestRoundRobinDoesNotMutateInput(t *testing.T) {
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inputs := map[string][]dns.RR{
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"addresses only": {
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test.A("a.example.org. 300 IN A 10.0.0.1"),
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test.A("a.example.org. 300 IN A 10.0.0.2"),
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test.A("a.example.org. 300 IN A 10.0.0.3"),
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test.A("a.example.org. 300 IN A 10.0.0.4"),
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},
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"mixed": {
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test.CNAME("a.example.org. 300 IN CNAME b.example.org."),
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test.A("b.example.org. 300 IN A 10.0.0.1"),
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test.A("b.example.org. 300 IN A 10.0.0.2"),
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test.MX("example.org. 300 IN MX 10 mx.example.org."),
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},
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}
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for name, in := range inputs {
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before := make([]dns.RR, len(in))
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copy(before, in)
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// Shuffle repeatedly: a single call may leave the order untouched by chance.
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for range 50 {
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out := roundRobin(in)
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if len(out) != len(in) {
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t.Fatalf("%s: got %d records back, want %d", name, len(out), len(in))
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}
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}
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for i := range in {
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if in[i] != before[i] {
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t.Errorf("%s: roundRobin reordered its input at index %d", name, i)
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break
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}
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}
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}
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}
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