refactor seek routine

tail.go

@@ -231,13 +231,11 @@ func (tail *Tail) tailFileSync() {
 					case <-tail.Dying():
 						return
 					}
-					_, err := tail.file.Seek(0, 2) // Seek to fine end
+					err = tail.seekEnd()
 					if err != nil {
-						tail.Killf("Seek error on %s: %s", tail.Filename, err)
+						tail.Kill(err)
 						return
 					}
-					// Reset the read buffer whenever the file is re-seek'ed
-					tail.reader.Reset(tail.file)
 				}
 			}
 		case io.EOF:
@@ -321,6 +319,16 @@ func (tail *Tail) newReader() *bufio.Reader {
 	}
 }
 
+func (tail *Tail) seekEnd() error {
+	_, err := tail.file.Seek(0, 2)
+	if err != nil {
+		return fmt.Errorf("Seek error on %s: %s", tail.Filename, err)
+	}
+	// Reset the read buffer whenever the file is re-seek'ed
+	tail.reader.Reset(tail.file)
+	return nil
+}
+
 // sendLine sends the line(s) to Lines channel, splitting longer lines
 // if necessary. Return false if rate limit is reached.
 func (tail *Tail) sendLine(line []byte) bool {

tail_test.go

@@ -268,7 +268,7 @@ func TestRateLimiting(_t *testing.T) {
 
 	// TODO: also verify that tail resumes after the cooloff period.
 	go t.VerifyTailOutput(
-		tail, 
+		tail,
 		[]string{"hello", "world", "again", expecting, "more", "data"})
 
 	// Add more data only after reasonable delay.