Merge pull request #6 from Alkorin/helpers

Helpers

helpers.go

@@ -0,0 +1,40 @@
+package cache
+
+import (
+	"time"
+)
+
+type timeOutResult struct {
+	r interface{}
+	e error
+}
+
+func WithTimeout(f cacheGetterFunc, t time.Duration, err error) cacheGetterFunc {
+	return func(v interface{}) (interface{}, error) {
+		c := make(chan timeOutResult)
+		go func() {
+			r, e := f(v)
+			c <- timeOutResult{r, e}
+		}()
+		select {
+		case r := <-c:
+			return r.r, r.e
+		case <-time.After(t):
+		}
+		return nil, err
+	}
+}
+
+func WithRetry(f cacheGetterFunc, n int) cacheGetterFunc {
+	return func(v interface{}) (interface{}, error) {
+		var lastError error
+		for i := 0; i < n; i++ {
+			r, e := f(v)
+			if e == nil {
+				return r, e
+			}
+			lastError = e
+		}
+		return nil, lastError
+	}
+}

helpers_test.go

@@ -0,0 +1,53 @@
+package cache
+
+import (
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestTimeout(t *testing.T) {
+	// Func which waits v and returns OK
+	f := func(v interface{}) (interface{}, error) {
+		time.Sleep(v.(time.Duration))
+		return "OK", nil
+	}
+
+	// Returns err if call is more than 100ms
+	f = WithTimeout(f, 100*time.Millisecond, errors.New("timed out"))
+
+	// Call with 50ms, should return 'OK'
+	if v, e := f(50 * time.Millisecond); v.(string) != "OK" || e != nil {
+		t.Fatalf("Should have returned OK, nil; received: %v, %v", v, e)
+	}
+
+	// Call with 200ms, should return 'timed out'
+	if v, e := f(200 * time.Millisecond); v != nil || e == nil || e.Error() != "timed out" {
+		t.Fatalf("Should have returned nil, 'timed out'; received: %v, %v", v, e)
+	}
+}
+
+func TestRetry(t *testing.T) {
+	nbCalled := 0
+	// Func which returns OK only at the second call
+	f := func(v interface{}) (interface{}, error) {
+		nbCalled++
+		if nbCalled == 2 {
+			return "OK", nil
+		}
+		return nil, errors.New("not second")
+	}
+
+	// Try to call func 3 times
+	f = WithRetry(f, 3)
+
+	// First try, should call the function 2 times and return success
+	if v, e := f(nil); nbCalled != 2 || v.(string) != "OK" || e != nil {
+		t.Fatalf("Should have returned 2, OK, nil; received: %v, %v, %v", nbCalled, v, e)
+	}
+
+	// Second try, should call the function 3 times and return error
+	if v, e := f(nil); nbCalled != 5 || v != nil || e == nil || e.Error() != "not second" {
+		t.Fatalf("Should have returned 5, nil, 'not second'; received: %v, %v, %v", nbCalled, v, e)
+	}
+}