Feature: add custom DNS support (#56)

common/cache/cache.go

@@ -0,0 +1,91 @@
+package cache
+
+import (
+	"runtime"
+	"sync"
+	"time"
+)
+
+// Cache store element with a expired time
+type Cache struct {
+	*cache
+}
+
+type cache struct {
+	mapping sync.Map
+	janitor *janitor
+}
+
+type element struct {
+	Expired time.Time
+	Payload interface{}
+}
+
+// Put element in Cache with its ttl
+func (c *cache) Put(key interface{}, payload interface{}, ttl time.Duration) {
+	c.mapping.Store(key, &element{
+		Payload: payload,
+		Expired: time.Now().Add(ttl),
+	})
+}
+
+// Get element in Cache, and drop when it expired
+func (c *cache) Get(key interface{}) interface{} {
+	item, exist := c.mapping.Load(key)
+	if !exist {
+		return nil
+	}
+	elm := item.(*element)
+	// expired
+	if time.Since(elm.Expired) > 0 {
+		c.mapping.Delete(key)
+		return nil
+	}
+	return elm.Payload
+}
+
+func (c *cache) cleanup() {
+	c.mapping.Range(func(k, v interface{}) bool {
+		key := k.(string)
+		elm := v.(*element)
+		if time.Since(elm.Expired) > 0 {
+			c.mapping.Delete(key)
+		}
+		return true
+	})
+}
+
+type janitor struct {
+	interval time.Duration
+	stop     chan struct{}
+}
+
+func (j *janitor) process(c *cache) {
+	ticker := time.NewTicker(j.interval)
+	for {
+		select {
+		case <-ticker.C:
+			c.cleanup()
+		case <-j.stop:
+			ticker.Stop()
+			return
+		}
+	}
+}
+
+func stopJanitor(c *Cache) {
+	c.janitor.stop <- struct{}{}
+}
+
+// New return *Cache
+func New(interval time.Duration) *Cache {
+	j := &janitor{
+		interval: interval,
+		stop:     make(chan struct{}),
+	}
+	c := &cache{janitor: j}
+	go j.process(c)
+	C := &Cache{c}
+	runtime.SetFinalizer(C, stopJanitor)
+	return C
+}

common/cache/cache_test.go

@@ -0,0 +1,70 @@
+package cache
+
+import (
+	"runtime"
+	"testing"
+	"time"
+)
+
+func TestCache_Basic(t *testing.T) {
+	interval := 200 * time.Millisecond
+	ttl := 20 * time.Millisecond
+	c := New(interval)
+	c.Put("int", 1, ttl)
+	c.Put("string", "a", ttl)
+
+	i := c.Get("int")
+	if i.(int) != 1 {
+		t.Error("should recv 1")
+	}
+
+	s := c.Get("string")
+	if s.(string) != "a" {
+		t.Error("should recv 'a'")
+	}
+}
+
+func TestCache_TTL(t *testing.T) {
+	interval := 200 * time.Millisecond
+	ttl := 20 * time.Millisecond
+	c := New(interval)
+	c.Put("int", 1, ttl)
+
+	i := c.Get("int")
+	if i.(int) != 1 {
+		t.Error("should recv 1")
+	}
+
+	time.Sleep(ttl * 2)
+	i = c.Get("int")
+	if i != nil {
+		t.Error("should recv nil")
+	}
+}
+
+func TestCache_AutoCleanup(t *testing.T) {
+	interval := 10 * time.Millisecond
+	ttl := 15 * time.Millisecond
+	c := New(interval)
+	c.Put("int", 1, ttl)
+
+	time.Sleep(ttl * 2)
+	i := c.Get("int")
+	if i != nil {
+		t.Error("should recv nil")
+	}
+}
+
+func TestCache_AutoGC(t *testing.T) {
+	sign := make(chan struct{})
+	go func() {
+		interval := 10 * time.Millisecond
+		ttl := 15 * time.Millisecond
+		c := New(interval)
+		c.Put("int", 1, ttl)
+		sign <- struct{}{}
+	}()
+
+	<-sign
+	runtime.GC()
+}

common/picker/picker.go

@@ -0,0 +1,22 @@
+package picker
+
+import "context"
+
+func SelectFast(ctx context.Context, in <-chan interface{}) <-chan interface{} {
+	out := make(chan interface{})
+	go func() {
+		select {
+		case p, open := <-in:
+			if open {
+				out <- p
+			}
+		case <-ctx.Done():
+		}
+
+		close(out)
+		for range in {
+		}
+	}()
+
+	return out
+}

common/picker/picker_test.go

@@ -0,0 +1,44 @@
+package picker
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func sleepAndSend(delay int, in chan<- interface{}, input interface{}) {
+	time.Sleep(time.Millisecond * time.Duration(delay))
+	in <- input
+}
+
+func sleepAndClose(delay int, in chan interface{}) {
+	time.Sleep(time.Millisecond * time.Duration(delay))
+	close(in)
+}
+
+func TestPicker_Basic(t *testing.T) {
+	in := make(chan interface{})
+	fast := SelectFast(context.Background(), in)
+	go sleepAndSend(20, in, 1)
+	go sleepAndSend(30, in, 2)
+	go sleepAndClose(40, in)
+
+	number, exist := <-fast
+	if !exist || number != 1 {
+		t.Error("should recv 1", exist, number)
+	}
+}
+
+func TestPicker_Timeout(t *testing.T) {
+	in := make(chan interface{})
+	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*5)
+	defer cancel()
+	fast := SelectFast(ctx, in)
+	go sleepAndSend(20, in, 1)
+	go sleepAndClose(30, in)
+
+	_, exist := <-fast
+	if exist {
+		t.Error("should recv false")
+	}
+}