Function TestNegativeStaleMaskingPositiveCache

plugin/cache/cache_test.go:622–706

(t *testing.T)

}

func TestNegativeStaleMaskingPositiveCache(t *testing.T) {
	c := New()
	c.staleUpTo = time.Minute * 10
	c.Next = nxDomainBackend(60)

	req := new(dns.Msg)
	qname := "cached.org."
	req.SetQuestion(qname, dns.TypeA)
	ctx := context.TODO()

	// Add an entry to Negative Cache": cached.org. = NXDOMAIN
	expectedResult := dns.RcodeNameError
	if ret, _ := c.ServeDNS(ctx, &test.ResponseWriter{}, req); ret != expectedResult {
		t.Errorf("Test 0 Negative Cache Population: expecting %v; got %v", expectedResult, ret)
	}

	// Confirm item was added to negative cache and not to positive cache
	if c.ncache.Len() == 0 {
		t.Errorf("Test 0 Negative Cache Population: item not added to negative cache")
	}
	if c.pcache.Len() != 0 {
		t.Errorf("Test 0 Negative Cache Population: item added to positive cache")
	}

	// Set the Backend to return non-cachable errors only
	c.Next = plugin.HandlerFunc(func(context.Context, dns.ResponseWriter, *dns.Msg) (int, error) {
		return 255, nil // Below, a 255 means we tried querying upstream.
	})

	// Confirm we get the NXDOMAIN from the negative cache, not the error form the backend
	rec := dnstest.NewRecorder(&test.ResponseWriter{})
	req = new(dns.Msg)
	req.SetQuestion(qname, dns.TypeA)
	expectedResult = dns.RcodeNameError
	if c.ServeDNS(ctx, rec, req); rec.Rcode != expectedResult {
		t.Errorf("Test 1 NXDOMAIN from Negative Cache: expecting %v; got %v", expectedResult, rec.Rcode)
	}

	// Jump into the future beyond when the negative cache item would go stale
	// but before the item goes rotten (exceeds serve stale time)
	c.now = func() time.Time { return time.Now().Add(time.Duration(5) * time.Minute) }

	// Set Backend to return a positive NOERROR + A record response
	c.Next = BackendHandler()

	// Make a query for the stale cache item
	rec = dnstest.NewRecorder(&test.ResponseWriter{})
	req = new(dns.Msg)
	req.SetQuestion(qname, dns.TypeA)
	expectedResult = dns.RcodeNameError
	if c.ServeDNS(ctx, rec, req); rec.Rcode != expectedResult {
		t.Errorf("Test 2 NOERROR from Backend: expecting %v; got %v", expectedResult, rec.Rcode)
	}

	// Confirm that prefetch removes the negative cache item.
	waitFor := 3
	for i := 1; i <= waitFor; i++ {
		if c.ncache.Len() != 0 {