Bug 43374

The DailyRollingFileAppender (DRFA) tries to rename the log file during roll over. 
However, when the rename fails, it ends up overwriting the log file, hence
loosing information.  In particular, on Windows, the file rename can fail if
another thread has the file open.

This problem was found in 1.2.8 and still exists in 1.2.15.

The problem was already described in bug 29726, but at that time the solution
was left to 1.3. Then it was again addressed in bug 41735, but only for
RollingFileAppender (RFA). I also talked about it on log4j-user ML
(http://mail-archives.apache.org/mod_mbox/logging-log4j-user/200709.mbox/%3cc8485ef10709040538k2074c3aag644f7b19a3a41e81@mail.gmail.com%3e).

I created a unit test that reproduces the problem (and also tests RFA), and made
a patch to solve this problem.

The problem was reproduced with both log4j 1.2.9 & 1.2.15 in the following
configurations (all combinations):
 - Win XP SP1, Win XP SP2, Win 2K3
 - JDK 1.4.2_03-b02, 1.5.0_10-b03, 1.6.0_02-b06
 - JUnit 3.8.1

The following patch applies on 1.2.15 and addresses the issue:
(I tested it in all the above configurations.)

Index: DailyRollingFileAppender.java
===================================================================
--- DailyRollingFileAppender.java	(revision 572567)
+++ DailyRollingFileAppender.java	(working copy)
@@ -319,16 +319,19 @@
 
     File file = new File(fileName);
     boolean result = file.renameTo(target);
+    boolean continueToAppend = false;
     if(result) {
       LogLog.debug(fileName +" -> "+ scheduledFilename);
     } else {
-      LogLog.error("Failed to rename ["+fileName+"] to ["+scheduledFilename+"].");
+      //   if file rename failed, reopen file with append = true
+      LogLog.warn("Failed to rename ["+fileName+"] to ["+scheduledFilename+"].");
+      continueToAppend = true;
     }
 
     try {
       // This will also close the file. This is OK since multiple
       // close operations are safe.
-      this.setFile(fileName, false, this.bufferedIO, this.bufferSize);
+      this.setFile(fileName, continueToAppend, this.bufferedIO, this.bufferSize);
     }
     catch(IOException e) {
       errorHandler.error("setFile("+fileName+", false) call failed.");