Round initialTime in RollingFileManager

Caching of filesystem timestamps (at least in ext4 on Linux) results in non-accurate creation timestamp.

Thus, let's round it to the second.

Rounding is also applied for the lastModified time, but I'm not sure whether it's needed there.

Fixes #3068.

Author: kelunik

log4j-core-test/src/test/java/org/apache/logging/log4j/core/appender/rolling/RollingFileManagerTest.java

@@ -224,4 +224,20 @@ void testRolloverOfDeletedFile() throws IOException {
         }
         assertEquals(testContent, new String(Files.readAllBytes(file.toPath()), StandardCharsets.US_ASCII));
     }
+
+    @Test
+    @Issue("https://github.com/apache/logging-log4j2/issues/3068")
+    void testInitialTimeRounded() throws IOException {
+        assertEquals(1755031147000L, RollingFileManager.alignMillisToSecond(1755031147000L));
+        assertEquals(1755031147000L, RollingFileManager.alignMillisToSecond(1755031147123L));
+        assertEquals(1755031147000L, RollingFileManager.alignMillisToSecond(1755031147499L));
+        assertEquals(1755031148000L, RollingFileManager.alignMillisToSecond(1755031147500L));
+        assertEquals(1755031148000L, RollingFileManager.alignMillisToSecond(1755031147999L));
+        assertEquals(1755031148000L, RollingFileManager.alignMillisToSecond(1755031148000L));
+
+        final File file = File.createTempFile("testFile", "log");
+        file.deleteOnExit();
+
+        assertEquals(0, RollingFileManager.initialFileTime(file) % 1000);
+    }
 }

log4j-core/src/main/java/org/apache/logging/log4j/core/appender/rolling/RollingFileManager.java

@@ -910,23 +910,32 @@ public RollingFileManager createManager(final String name, final FactoryData dat
         }
     }
 
-    private static long initialFileTime(final File file) {
+    static long initialFileTime(final File file) {
         final Path path = file.toPath();
         if (Files.exists(path)) {
             try {
                 final BasicFileAttributes attrs = Files.readAttributes(path, BasicFileAttributes.class);
                 final FileTime fileTime = attrs.creationTime();
                 if (fileTime.compareTo(EPOCH) > 0) {
                     LOGGER.debug("Returning file creation time for {}", file.getAbsolutePath());
-                    return fileTime.toMillis();
+
+                    return alignMillisToSecond(fileTime.toMillis());
                 }
-                LOGGER.info("Unable to obtain file creation time for " + file.getAbsolutePath());
+                LOGGER.info("Unable to obtain file creation time for {}", file.getAbsolutePath());
             } catch (final Exception ex) {
-                LOGGER.info("Unable to calculate file creation time for " + file.getAbsolutePath() + ": "
-                        + ex.getMessage());
+                LOGGER.info(
+                        "Unable to calculate file creation time for {}: {}", file.getAbsolutePath(), ex.getMessage());
             }
         }
-        return file.lastModified();
+
+        return alignMillisToSecond(file.lastModified());
+    }
+
+    /**
+     * @see <a href="https://github.com/apache/logging-log4j2/issues/3068">Issue #3068</a>
+     */
+    static long alignMillisToSecond(long millis) {
+        return Math.round(millis / 1000d) * 1000;
     }
 
     private static class EmptyQueue extends ArrayBlockingQueue<Runnable> {