Enable loss less rotation of log files

log/logger_test.go

@@ -0,0 +1,79 @@
+package log
+
+import (
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestLogRotation(t *testing.T) {
+	tempDir, err := ioutil.TempDir("", "traefik_")
+	if err != nil {
+		t.Fatalf("Error setting up temporary directory: %s", err)
+	}
+
+	fileName := tempDir + "traefik.log"
+	if err := OpenFile(fileName); err != nil {
+		t.Fatalf("Error opening temporary file %s: %s", fileName, err)
+	}
+	defer CloseFile()
+
+	rotatedFileName := fileName + ".rotated"
+
+	iterations := 20
+	halfDone := make(chan bool)
+	writeDone := make(chan bool)
+	go func() {
+		for i := 0; i < iterations; i++ {
+			Println("Test log line")
+			if i == iterations/2 {
+				halfDone <- true
+			}
+		}
+		writeDone <- true
+	}()
+
+	<-halfDone
+	err = os.Rename(fileName, rotatedFileName)
+	if err != nil {
+		t.Fatalf("Error renaming file: %s", err)
+	}
+
+	err = RotateFile()
+	if err != nil {
+		t.Fatalf("Error rotating file: %s", err)
+	}
+
+	select {
+	case <-writeDone:
+		gotLineCount := lineCount(t, fileName) + lineCount(t, rotatedFileName)
+		if iterations != gotLineCount {
+			t.Errorf("Wanted %d written log lines, got %d", iterations, gotLineCount)
+		}
+	case <-time.After(500 * time.Millisecond):
+		t.Fatalf("test timed out")
+	}
+
+	close(halfDone)
+	close(writeDone)
+}
+
+func lineCount(t *testing.T, fileName string) int {
+	t.Helper()
+	fileContents, err := ioutil.ReadFile(fileName)
+	if err != nil {
+		t.Fatalf("Error reading from file %s: %s", fileName, err)
+	}
+
+	count := 0
+	for _, line := range strings.Split(string(fileContents), "\n") {
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
+		count++
+	}
+
+	return count
+}