Feature: implemented a strategy similar to optimistic DNS (#647)

common/cache/lrucache_test.go

@@ -136,3 +136,31 @@ func TestEvict(t *testing.T) {
 
 	assert.Equal(t, temp, 3)
 }
+
+func TestSetWithExpire(t *testing.T) {
+	c := NewLRUCache(WithAge(1))
+	now := time.Now().Unix()
+
+	tenSecBefore := time.Unix(now-10, 0)
+	c.SetWithExpire(1, 2, tenSecBefore)
+
+	// res is expected not to exist, and expires should be empty time.Time
+	res, expires, exist := c.GetWithExpire(1)
+	assert.Equal(t, nil, res)
+	assert.Equal(t, time.Time{}, expires)
+	assert.Equal(t, false, exist)
+
+}
+
+func TestStale(t *testing.T) {
+	c := NewLRUCache(WithAge(1), WithStale(true))
+	now := time.Now().Unix()
+
+	tenSecBefore := time.Unix(now-10, 0)
+	c.SetWithExpire(1, 2, tenSecBefore)
+
+	res, expires, exist := c.GetWithExpire(1)
+	assert.Equal(t, 2, res)
+	assert.Equal(t, tenSecBefore, expires)
+	assert.Equal(t, true, exist)
+}