git » dnss » commit 45365ba

diff --git a/internal/dnstox/caching_test.go b/internal/dnstox/caching_test.go
new file mode 100644
index 0000000..f798f2b
--- /dev/null
+++ b/internal/dnstox/caching_test.go
@@ -0,0 +1,339 @@
+package dnstox
+
+// Tests for the caching resolver.
+// Note the other resolvers have more functional tests in the testing/
+// directory.
+
+import (
+	"fmt"
+	"reflect"
+	"strconv"
+	"testing"
+	"time"
+
+	"blitiri.com.ar/go/dnss/testing/util"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/trace"
+)
+
+// A test resolver that we use as backing for the caching resolver under test.
+type TestResolver struct {
+	// Has this resolver been initialized?
+	init bool
+
+	// Maintain() sends a value over this channel.
+	maintain chan bool
+
+	// The last query we've seen.
+	lastQuery *dns.Msg
+
+	// What we will respond to queries.
+	response  *dns.Msg
+	respError error
+}
+
+func NewTestResolver() *TestResolver {
+	return &TestResolver{
+		maintain: make(chan bool, 1),
+	}
+}
+
+func (r *TestResolver) Init() error {
+	r.init = true
+	return nil
+}
+
+func (r *TestResolver) Maintain() {
+	r.maintain <- true
+}
+
+func (r *TestResolver) Query(req *dns.Msg, tr trace.Trace) (*dns.Msg, error) {
+	r.lastQuery = req
+	if r.response != nil {
+		r.response.Question = req.Question
+		r.response.Authoritative = true
+	}
+	return r.response, r.respError
+}
+
+//
+// === Tests ===
+//
+
+// Test basic functionality.
+func TestBasic(t *testing.T) {
+	r := NewTestResolver()
+
+	c := NewCachingResolver(r)
+
+	c.Init()
+	if !r.init {
+		t.Errorf("caching resolver did not initialize backing")
+	}
+	go c.Maintain()
+
+	// Check that the back resolver's Maintain() is called.
+	select {
+	case <-r.maintain:
+		t.Log("Maintain() called")
+	case <-time.After(1 * time.Second):
+		t.Errorf("back resolver Maintain() was not called")
+	}
+
+	resetStats()
+
+	resp := queryA(t, c, "test. A 1.2.3.4", "test.", "1.2.3.4")
+	if !statsEquals(1, 0, 1) {
+		t.Errorf("bad stats: %v", dumpStats())
+	}
+	if !resp.Authoritative {
+		t.Errorf("cache miss was not authoritative")
+	}
+
+	// Same query, should be cached.
+	resp = queryA(t, c, "", "test.", "1.2.3.4")
+	if !statsEquals(2, 1, 1) {
+		t.Errorf("bad stats: %v", dumpStats())
+	}
+	if resp.Authoritative {
+		t.Errorf("cache hit was authoritative")
+	}
+}
+
+// Test TTL handling.
+func TestTTL(t *testing.T) {
+	r := NewTestResolver()
+	c := NewCachingResolver(r)
+	c.Init()
+	resetStats()
+
+	// Note we don't start c.Maintain() yet, as we don't want the background
+	// TTL updater until later.
+
+	// Test a record with a larger-than-max TTL (1 day).
+	// The TTL of the response should be capped.
+	resp := queryA(t, c, "test. 86400 A 1.2.3.4", "test.", "1.2.3.4")
+	if !statsEquals(1, 0, 1) {
+		t.Errorf("bad stats: %v", dumpStats())
+	}
+	if ttl := getTTL(resp.Answer); ttl != maxTTL {
+		t.Errorf("expected max TTL (%v), got %v", maxTTL, ttl)
+	}
+
+	// Same query, should be cached, and TTL also capped.
+	// As we've not enabled cache maintenance, we can be sure TTL == maxTTL.
+	resp = queryA(t, c, "", "test.", "1.2.3.4")
+	if !statsEquals(2, 1, 1) {
+		t.Errorf("bad stats: %v", dumpStats())
+	}
+	if ttl := getTTL(resp.Answer); ttl != maxTTL {
+		t.Errorf("expected max TTL (%v), got %v", maxTTL, ttl)
+	}
+
+	// To test that the TTL is reduced appropriately, set a small maintenance
+	// period, and then repeatedly query the record. We should see its TTL
+	// shrinking down within 1s.
+	// Even though the TTL resolution in the protocol is in seconds, we don't
+	// need to wait that much "thanks" to rounding artifacts.
+	maintenancePeriod = 50 * time.Millisecond
+	go c.Maintain()
+	resetStats()
+
+	start := time.Now()
+	for time.Since(start) < 1*time.Second {
+		resp = queryA(t, c, "", "test.", "1.2.3.4")
+		t.Logf("TTL %v", getTTL(resp.Answer))
+		if ttl := getTTL(resp.Answer); ttl <= (maxTTL - 1*time.Second) {
+			break
+		}
+		time.Sleep(maintenancePeriod)
+	}
+	if ttl := getTTL(resp.Answer); ttl > (maxTTL - 1*time.Second) {
+		t.Errorf("expected maxTTL-1s, got %v", ttl)
+	}
+}
+
+// Test that we don't cache failed queries.
+func TestFailedQueries(t *testing.T) {
+	r := NewTestResolver()
+	c := NewCachingResolver(r)
+	c.Init()
+	resetStats()
+
+	// Do two failed identical queries, check that both are cache misses.
+	queryFail(t, c)
+	if !statsEquals(1, 0, 1) {
+		t.Errorf("bad stats: %v", dumpStats())
+	}
+
+	queryFail(t, c)
+	if !statsEquals(2, 0, 2) {
+		t.Errorf("bad stats: %v", dumpStats())
+	}
+}
+
+// Test that we handle the cache filling up.
+// Note this test is tied to the current behaviour of not doing any eviction
+// when we're full, which is not ideal and will likely be changed in the
+// future.
+func TestCacheFull(t *testing.T) {
+	r := NewTestResolver()
+	c := NewCachingResolver(r)
+	c.Init()
+	resetStats()
+
+	r.response = newReply(mustNewRR(t, "test. A 1.2.3.4"))
+
+	// Do maxCacheSize+1 different requests.
+	for i := 0; i < maxCacheSize+1; i++ {
+		queryA(t, c, "", fmt.Sprintf("test%d.", i), "1.2.3.4")
+		if !statsEquals(i+1, 0, i+1) {
+			t.Errorf("bad stats: %v", dumpStats())
+		}
+	}
+
+	// Query up to maxCacheSize, they should all be hits.
+	resetStats()
+	for i := 0; i < maxCacheSize; i++ {
+		queryA(t, c, "", fmt.Sprintf("test%d.", i), "1.2.3.4")
+		if !statsEquals(i+1, i+1, 0) {
+			t.Errorf("bad stats: %v", dumpStats())
+		}
+	}
+
+	// Querying maxCacheSize+1 should be a miss, because the cache was full.
+	resetStats()
+	queryA(t, c, "", fmt.Sprintf("test%d.", maxCacheSize), "1.2.3.4")
+	if !statsEquals(1, 0, 1) {
+		t.Errorf("bad stats: %v", dumpStats())
+	}
+}
+
+// Test behaviour when the size of the cache is 0 (so users can disable it
+// that way).
+func TestZeroSize(t *testing.T) {
+	r := NewTestResolver()
+	c := NewCachingResolver(r)
+	c.Init()
+	resetStats()
+
+	// Override the max cache size to 0.
+	prevMaxCacheSize := maxCacheSize
+	maxCacheSize = 0
+	defer func() { maxCacheSize = prevMaxCacheSize }()
+
+	r.response = newReply(mustNewRR(t, "test. A 1.2.3.4"))
+
+	// Do 5 different requests.
+	for i := 0; i < 5; i++ {
+		queryA(t, c, "", fmt.Sprintf("test%d.", i), "1.2.3.4")
+		if !statsEquals(i+1, 0, i+1) {
+			t.Errorf("bad stats: %v", dumpStats())
+		}
+	}
+
+	// Query them back, they should all be misses.
+	resetStats()
+	for i := 0; i < 5; i++ {
+		queryA(t, c, "", fmt.Sprintf("test%d.", i), "1.2.3.4")
+		if !statsEquals(i+1, 0, i+1) {
+			t.Errorf("bad stats: %v", dumpStats())
+		}
+	}
+}
+
+//
+// === Helpers ===
+//
+
+func resetStats() {
+	stats.cacheTotal.Set(0)
+	stats.cacheBypassed.Set(0)
+	stats.cacheHits.Set(0)
+	stats.cacheMisses.Set(0)
+	stats.cacheRecorded.Set(0)
+}
+
+func statsEquals(total, hits, misses int) bool {
+	return (stats.cacheTotal.String() == strconv.Itoa(total) &&
+		stats.cacheHits.String() == strconv.Itoa(hits) &&
+		stats.cacheMisses.String() == strconv.Itoa(misses))
+}
+
+func dumpStats() string {
+	return fmt.Sprintf("(t:%v  h:%s  m:%v)",
+		stats.cacheTotal, stats.cacheHits, stats.cacheMisses)
+}
+
+func queryA(t *testing.T, c *cachingResolver, rr, domain, expected string) *dns.Msg {
+	// Set up the response from the given RR (if any).
+	if rr != "" {
+		back := c.back.(*TestResolver)
+		back.response = newReply(mustNewRR(t, rr))
+	}
+
+	tr := util.NewTestTrace(t)
+	defer tr.Finish()
+
+	req := newQuery(domain, dns.TypeA)
+	resp, err := c.Query(req, tr)
+	if err != nil {
+		t.Fatalf("query failed: %v", err)
+	}
+
+	a := resp.Answer[0].(*dns.A)
+	if a.A.String() != expected {
+		t.Errorf("expected %s, got %v", expected, a.A)
+	}
+
+	if !reflect.DeepEqual(req.Question, resp.Question) {
+		t.Errorf("question mis-match: request %v, response %v",
+			req.Question, resp.Question)
+	}
+
+	return resp
+}
+
+func queryFail(t *testing.T, c *cachingResolver) *dns.Msg {
+	back := c.back.(*TestResolver)
+	back.response = &dns.Msg{}
+	back.response.Response = true
+	back.response.Rcode = dns.RcodeNameError
+
+	tr := util.NewTestTrace(t)
+	defer tr.Finish()
+
+	req := newQuery("doesnotexist.", dns.TypeA)
+	resp, err := c.Query(req, tr)
+	if err != nil {
+		t.Fatalf("query failed: %v", err)
+	}
+
+	return resp
+}
+
+func mustNewRR(t *testing.T, s string) dns.RR {
+	rr, err := dns.NewRR(s)
+	if err != nil {
+		t.Fatalf("invalid RR %q: %v", s, err)
+	}
+	return rr
+}
+
+func newQuery(domain string, t uint16) *dns.Msg {
+	m := &dns.Msg{}
+	m.SetQuestion(domain, t)
+	return m
+}
+
+func newReply(answer dns.RR) *dns.Msg {
+	return &dns.Msg{
+		MsgHdr: dns.MsgHdr{
+			Response:      true,
+			Authoritative: false,
+			Rcode:         dns.RcodeSuccess,
+		},
+		Answer: []dns.RR{answer},
+	}
+}
diff --git a/internal/dnstox/resolver.go b/internal/dnstox/resolver.go
index 831d8b4..a90326b 100644
--- a/internal/dnstox/resolver.go
+++ b/internal/dnstox/resolver.go
@@ -289,7 +289,9 @@ func NewCachingResolver(back Resolver) *cachingResolver {
 	}
 }
 
-const (
+// Constants that tune the cache.
+// They are declared as variables so we can tweak them for testing.
+var (
 	// Maximum number of entries we keep in the cache.
 	// 2k should be reasonable for a small network.
 	// Keep in mind that increasing this too much will interact negatively
diff --git a/testing/util/util.go b/testing/util/util.go
index 9964691..1f046a2 100644
--- a/testing/util/util.go
+++ b/testing/util/util.go
@@ -3,6 +3,7 @@ package util
 
 import (
 	"fmt"
+	"testing"
 	"time"
 
 	"github.com/miekg/dns"
@@ -38,3 +39,28 @@ func WaitForDNSServer(addr string) error {
 
 	return fmt.Errorf("not reachable")
 }
+
+// TestTrace implements the tracer.Trace interface, but prints using the test
+// logging infrastructure.
+type TestTrace struct {
+	T *testing.T
+}
+
+func NewTestTrace(t *testing.T) *TestTrace {
+	return &TestTrace{t}
+}
+
+func (t *TestTrace) LazyLog(x fmt.Stringer, sensitive bool) {
+	t.T.Logf("trace %p (%b): %s", t, sensitive, x)
+}
+
+func (t *TestTrace) LazyPrintf(format string, a ...interface{}) {
+	prefix := fmt.Sprintf("trace %p: ", t)
+	t.T.Logf(prefix+format, a...)
+}
+
+func (t *TestTrace) SetError()                           {}
+func (t *TestTrace) SetRecycler(f func(interface{}))     {}
+func (t *TestTrace) SetTraceInfo(traceID, spanID uint64) {}
+func (t *TestTrace) SetMaxEvents(m int)                  {}
+func (t *TestTrace) Finish()                             {}