Retention

Logfiles are often large. Logging providers allow retention policies to be configured.

Retention has to balance:

The need to index logs before they're removed.
The need to retain logs for other (including regulatory) purposes.

Defaults are subject to change. Currently they are:

Files <= 50MB before rollover.
Files retain for 30 days.
Total files capped at 10GB.

In Logback configuration XML:

<appender name="file" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${outputDirectory}/${outputFilename}.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
        <fileNamePattern>${outputDirectory}/${outputFilename}.%d{yyyy-MM-dd}.%i.log.zip</fileNamePattern>
        <maxFileSize>50MB</maxFileSize>
        <maxHistory>30</maxHistory>
        <totalSizeCap>10GB</totalSizeCap>
    </rollingPolicy>
    <encoder>
        <!-- ... -->
    </encoder>
</appender>