Major Description
Suppose I have an appender configured like so:
<RollingFile name="test"
fileName="logs/test"
filePattern="logs/test.%d
">
<PatternLayout pattern="%d
%-5level %message%n"/>
<TimeBasedTriggeringPolicy interval="1" modulate="true"/>
</RollingFile>
Supposed today is 2012-11-13, and thus tomorrow is 2012-11-14.
I create several logging events today, and as expected they end up in a file named "logs/test"
Midnight goes by, and it is now the 14th. Some more logging events occur around 12:01 am.
What I expect to see after this is:
logs/test
logs/test.2012-11-13
What I actually end up seeing is:
logs/test
logs/test.2012-11-14
So the archived entries of the 13th are in a file name matching the 14th. That is quite confusing!
I tested this with some other formats, and it seems that no matter what is the most specific (day, hour, minute, etc.) field, it is always higher than expected.
I traced through the code, and the culprit seems to be in PatternProcessor:
protected final void formatFileName(final Object obj, final StringBuilder buf) {
Object[] objects = new Object[]
;
formatFileName(objects, buf);
}
So the Date being used for the filename is the current time when the name is computed, which is guaranteed to be within an interval that is after the one of the file contents. If I went a copule of intervals (in this case days) without log events, then it could be stamped with a name that is several days after the contents.
In the latter case, I'm not sure if I'd expect to see a filename with the 13th still, or maybe the 15th (assuming rollover happened during the 16th). But in either case, I definitely don't expect to see a filename with the 16th, which is what I'd get.