Add ability to capture logs

main.go

@@ -33,6 +33,7 @@ type Client struct {
 	MaxRetries  int
 	Backoff     BackoffStrategy
 	KeepLog     bool
+	LogHook     LogHook
 
 	SuccessReqNum   int
 	SuccessRetryNum int
@@ -95,6 +96,10 @@ func NewExtendedClient(hc *http.Client) *Client {
 	return c
 }
 
+// PrintErrStrategy is used to log attempts as they happen.
+// You know, more visible
+type LogHook func(e ErrEntry)
+
 // BackoffStrategy is used to determine how long a retry request should wait until attempted
 type BackoffStrategy func(retry int) time.Duration
 
@@ -336,12 +341,17 @@ func (c *Client) LogString() string {
 	defer c.Unlock()
 	var res string
 	for _, e := range c.ErrLog {
-		res += fmt.Sprintf("%d %s [%s] %s request-%d retry-%d error: %s\n",
-			e.Time.Unix(), e.Method, e.Verb, e.URL, e.Request, e.Retry, e.Err)
+		res += c.FormatError(e)
 	}
 	return res
 }
 
+// Format the Error to human readable string
+func (c *Client) FormatError(e ErrEntry) string {
+	return fmt.Sprintf("%d %s [%s] %s request-%d retry-%d error: %s\n",
+		e.Time.Unix(), e.Method, e.Verb, e.URL, e.Request, e.Retry, e.Err)
+}
+
 // LogErrCount is a helper method used primarily for test validation
 func (c *Client) LogErrCount() int {
 	c.Lock()
@@ -358,8 +368,12 @@ func (c *Client) EmbedHTTPClient(hc *http.Client) {
 func (c *Client) log(e ErrEntry) {
 	if c.KeepLog {
 		c.Lock()
+		defer c.Unlock()
 		c.ErrLog = append(c.ErrLog, e)
-		c.Unlock()
+	} else if c.LogHook != nil {
+		// NOTE: There is a possibility that Log Printing hook slows it down.
+		// but the consumer can always do the Job in a go-routine.
+		c.LogHook(e)
 	}
 }
 

main_test.go

@@ -100,6 +100,63 @@ func TestDefaultBackoff(t *testing.T) {
 
 }
 
+func TestCustomLogHook(t *testing.T) {
+	t.Parallel()
+
+	expectedRetries := 5
+	errorLines := []ErrEntry{}
+
+	c := New()
+	//c.KeepLog = true
+	c.MaxRetries = expectedRetries
+	c.Backoff = func(_ int) time.Duration {
+		return 10 * time.Microsecond
+	}
+
+	c.LogHook = func(e ErrEntry) {
+		errorLines = append(errorLines, e)
+	}
+
+	nonExistantURL := "http://localhost:9000/foo"
+
+	_, err := c.Get(nonExistantURL)
+	if err == nil {
+		t.Fatal("expected to get an error")
+	}
+	c.Wait()
+
+	// in the event of an error, let's see what the logs were
+	if expectedRetries != len(errorLines) {
+		t.Errorf("Expected %d lines to be emitted. Got %d", expectedRetries, errorLines)
+	}
+}
+
+func TestDefaultLogHook(t *testing.T) {
+	t.Parallel()
+
+	errorLines := 0
+
+	c := New()
+	//c.KeepLog = true
+	c.MaxRetries = 5
+	c.Backoff = func(_ int) time.Duration {
+		return 10 * time.Microsecond
+	}
+
+	nonExistantURL := "http://localhost:9000/foo"
+
+	_, err := c.Get(nonExistantURL)
+	if err == nil {
+		t.Fatal("expected to get an error")
+	}
+	c.Wait()
+
+	// in the event of an error, let's see what the logs were
+	if errorLines != 0 {
+		t.Errorf("Expected 0 lines to be emitted. Got %d", errorLines)
+	}
+}
+
 func TestLinearJitterBackoff(t *testing.T) {
 	t.Parallel()
 	c := New()