https://issues.apache.org/bugzilla/show_bug.cgi?id=49920
Summary: DailyRollingFileAppender.rollOver() might leave
superclass's WriterAppender.qw as null causing
NullPointerExceptions when logging events
Product: Log4j
Version: 1.2
Platform: PC
OS/Version: Linux
Status: NEW
Severity: major
Priority: P2
Component: Appender
AssignedTo: [email protected]
ReportedBy: [email protected]
DailyRollingFileAppender.rollOver() method catch a FileNotFoundException from
FileAppender superclass setFile method:
this.setFile(fileName, true, this.bufferedIO, this.bufferSize);
When this exception is thrown, WriterAppender.qw might be left as null causing
all further subAppend(LoggingEvent) invocations failed with
NullPointerException.
I noticed that setFile might fail with FileNotFoundException when the
filesystem is full and even an empty file cannot be created. The scenario is as
follows (code from
http://repo1.maven.org/maven2/log4j/log4j/1.2.16/log4j-1.2.16-sources.jar):
1. current log file name is "test.log"
2. a filesystem where test.log is kept become full
3. DailyRollingFileAppender.rollOver() method successfully closes current
(test.log) file and successfully renames it to a timestamped file
(test.log.yyyy-MM-dd)
4. DailyRollingFileAppender.rollOver() calls setFile from FileAppender
superclass to open the current log file (test.log) again. When setFile is
called that file doesn't exist as it was previously renamed to a timestamped
filename. Following code from FileAppender.setFile(...) will throw
FileNotFoundException:
FileOutputStream ostream = null;
try {
//
// attempt to create file
//
ostream = new FileOutputStream(fileName, append);
} catch(FileNotFoundException ex) {
//
// if parent directory does not exist then
// attempt to create it and try to create file
// see bug 9150
//
String parentName = new File(fileName).getParent();
if (parentName != null) {
File parentDir = new File(parentName);
if(!parentDir.exists() && parentDir.mkdirs()) {
ostream = new FileOutputStream(fileName, append);
} else {
throw ex;
}
} else {
throw ex;
}
}
FileNotFoundException can be thrown if it is impossible to create a new empty
file when the filesystem is full.
5. DailyRollingFileAppender.rollOver() will catch that exception and log it
using error handler and then continue its flow. It will leave its QuietWriter
qw field set to null.
Each next logging event passed to subAppend method will cause
NullPointerException (and in case of AsyncAppender calling it will cause
AsyncAppender async thread to die as it doesn't catch NPE).
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