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package cache
import (
"context"
"fmt"
"testing"
"time"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/pkg/dnstest"
"github.com/coredns/coredns/plugin/test"
"github.com/miekg/dns"
)
func TestPrefetch(t *testing.T) {
tests := []struct {
qname string
ttl int
prefetch int
verifications []verification
}{
{
qname: "hits.reset.example.org.",
ttl: 80,
prefetch: 1,
verifications: []verification{
{
after: 0 * time.Second,
answer: "hits.reset.example.org. 80 IN A 127.0.0.1",
fetch: true, // Initial fetch
},
{
after: 73 * time.Second,
answer: "hits.reset.example.org. 7 IN A 127.0.0.1",
fetch: true, // Triggers prefetch with 7 TTL (10% of 80 = 8 TTL threshold)
},
{
after: 80 * time.Second,
answer: "hits.reset.example.org. 73 IN A 127.0.0.2",
},
},
},
{
qname: "short.ttl.example.org.",
ttl: 5,
prefetch: 1,
verifications: []verification{
{
after: 0 * time.Second,
answer: "short.ttl.example.org. 5 IN A 127.0.0.1",
fetch: true,
},
{
after: 1 * time.Second,
answer: "short.ttl.example.org. 4 IN A 127.0.0.1",
},
{
after: 4 * time.Second,
answer: "short.ttl.example.org. 1 IN A 127.0.0.1",
fetch: true,
},
{
after: 5 * time.Second,
answer: "short.ttl.example.org. 4 IN A 127.0.0.2",
},
},
},
{
qname: "no.prefetch.example.org.",
ttl: 30,
prefetch: 0,
verifications: []verification{
{
after: 0 * time.Second,
answer: "no.prefetch.example.org. 30 IN A 127.0.0.1",
fetch: true,
},
{
after: 15 * time.Second,
answer: "no.prefetch.example.org. 15 IN A 127.0.0.1",
},
{
after: 29 * time.Second,
answer: "no.prefetch.example.org. 1 IN A 127.0.0.1",
},
{
after: 30 * time.Second,
answer: "no.prefetch.example.org. 30 IN A 127.0.0.2",
fetch: true,
},
},
},
{
// tests whether cache prefetches with the do bit
qname: "do.prefetch.example.org.",
ttl: 80,
prefetch: 1,
verifications: []verification{
{
after: 0 * time.Second,
answer: "do.prefetch.example.org. 80 IN A 127.0.0.1",
do: true,
fetch: true,
},
{
after: 73 * time.Second,
answer: "do.prefetch.example.org. 7 IN A 127.0.0.1",
do: true,
fetch: true,
},
{
after: 80 * time.Second,
answer: "do.prefetch.example.org. 73 IN A 127.0.0.2",
do: true,
},
{
// Should be 127.0.0.3 as 127.0.0.2 was the prefetch WITH do bit
after: 80 * time.Second,
answer: "do.prefetch.example.org. 80 IN A 127.0.0.3",
fetch: true,
},
},
},
{
// tests whether cache prefetches with the cd bit
qname: "cd.prefetch.example.org.",
ttl: 80,
prefetch: 1,
verifications: []verification{
{
after: 0 * time.Second,
answer: "cd.prefetch.example.org. 80 IN A 127.0.0.1",
cd: true,
fetch: true,
},
{
after: 73 * time.Second,
answer: "cd.prefetch.example.org. 7 IN A 127.0.0.1",
cd: true,
fetch: true,
},
{
after: 80 * time.Second,
answer: "cd.prefetch.example.org. 73 IN A 127.0.0.2",
cd: true,
},
{
// Should be 127.0.0.3 as 127.0.0.2 was the prefetch WITH cd bit
after: 80 * time.Second,
answer: "cd.prefetch.example.org. 80 IN A 127.0.0.3",
fetch: true,
},
},
},
}
t0, err := time.Parse(time.RFC3339, "2018-01-01T14:00:00+00:00")
if err != nil {
t.Fatal(err)
}
for _, tt := range tests {
t.Run(tt.qname, func(t *testing.T) {
fetchc := make(chan struct{}, 1)
c := New()
c.Next = prefetchHandler(tt.qname, tt.ttl, fetchc)
c.prefetch = tt.prefetch
rec := dnstest.NewRecorder(&test.ResponseWriter{})
for _, v := range tt.verifications {
c.now = func() time.Time { return t0.Add(v.after) }
req := new(dns.Msg)
req.SetQuestion(tt.qname, dns.TypeA)
req.CheckingDisabled = v.cd
req.SetEdns0(512, v.do)
c.ServeDNS(context.TODO(), rec, req)
if v.fetch {
select {
case <-fetchc:
// Prefetch handler was called.
case <-time.After(time.Second):
t.Fatalf("After %s: want request to trigger a prefetch", v.after)
}
}
if want, got := dns.RcodeSuccess, rec.Rcode; want != got {
t.Errorf("After %s: want rcode %d, got %d", v.after, want, got)
}
if want, got := 1, len(rec.Msg.Answer); want != got {
t.Errorf("After %s: want %d answer RR, got %d", v.after, want, got)
}
if want, got := test.A(v.answer).String(), rec.Msg.Answer[0].String(); want != got {
t.Errorf("After %s: want answer %s, got %s", v.after, want, got)
}
}
})
}
}
type verification struct {
after time.Duration
answer string
do bool
cd bool
// fetch defines whether a request is sent to the next handler.
fetch bool
}
// prefetchHandler is a fake plugin implementation which returns a single A
// record with the given qname and ttl. The returned IP address starts at
// 127.0.0.1 and is incremented on every request.
func prefetchHandler(qname string, ttl int, fetchc chan struct{}) plugin.Handler {
i := 0
return plugin.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
i++
m := new(dns.Msg)
m.SetQuestion(qname, dns.TypeA)
m.Response = true
m.Answer = append(m.Answer, test.A(fmt.Sprintf("%s %d IN A 127.0.0.%d", qname, ttl, i)))
w.WriteMsg(m)
fetchc <- struct{}{}
return dns.RcodeSuccess, nil
})
}
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