Size Based Triggering Policy

SizeBasedTriggeringPolicy looks at the size of the currently active file. If it grows larger than the specified size, it will signal the owning RollingFileAppender to trigger the rollover of the existing active file.

SizeBasedTriggeringPolicy accepts only one parameter, namely maxFileSize, with a default value of 10 MB.

The maxFileSize option can be specified in bytes, kilobytes, megabytes or gigabytes by suffixing a numeric value with KB, MB and respectively GB. For example, 5000000, 5000KB, 5MB and 2GB are all valid values, with the first three being equivalent.

Here is a sample configuration with a RollingFileAppender in conjunction with SizeBasedTriggeringPolicy triggering rollover when the log file reaches 5MB in size.

Example: Sample configuration of a RollingFileAppender using a SizeBasedTriggeringPolicy (logback-examples/src/main/resources/chapters/appenders/conf/logback-RollingSizeBased.xml)

<configuration>
  <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>test.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
      <fileNamePattern>test.%i.log.zip</fileNamePattern>
      <minIndex>1</minIndex>
      <maxIndex>3</maxIndex>
    </rollingPolicy>

    <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
      <maxFileSize>5MB</maxFileSize>
    </triggeringPolicy>
    <encoder>
      <pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern>
    </encoder>
  </appender>

  <root level="DEBUG">
    <appender-ref ref="FILE" />
  </root>
</configuration>