While doing some testing I've encountered a situation where we generate a large number of log files. They seem to be rotating as expected, except for directly after a restart of the application. When that happens, logback writes a few messages to each file, starting at index 101 until it reaches the current file, at which point it resumes working normally.

For example, the logs should rotate each month, and grow up to 10MB before rotating. As each rotates its log index will increase (2012-01.1.log, 2012-01.2.log, ..., 2012-01.891.log). logback is writing the first few messages to 2012-01.101.log and then walks up each log after that, writing a few log messages before moving on (presumably "realizing" that each log is at its size threshold).

I'm puzzled that it starts at 2012-01.101.log (2012-01.1.log would make more sense). It's even more puzzling that it writes anything to the lower logs in the first place. Any ideas why this is happening?

Here is my configuration:

<configuration debug="false">
<turboFilter class="ch.qos.logback.classic.turbo.MarkerFilter">
     <Marker>ALWAYS</Marker>
     <OnMatch>ACCEPT</OnMatch>
   </turboFilter>

<appender name="R" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <prudent>true</prudent>
    <encoder>
    <Pattern>%d %p [%t] %X{user} %X{session} %F:%L - %m%n</Pattern>
    </encoder>
    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
    <FileNamePattern>${catalina.home}/logs/tomcat.%d{yyyy-MM}.%i.log</FileNamePattern>
      <TimeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
        <maxFileSize>10MB</maxFileSize>
      </TimeBasedFileNamingAndTriggeringPolicy>
      <maxHistory>2</maxHistory>
    </rollingPolicy>
</appender>

<logger name="org.apache.catalina.startup.Catalina" level="INFO" />

<root level="warn">
    <appender-ref ref="R"/>
</root>
</configuration>