[logback-user] RollingFileAppender with Prudent Flag

[Thomas.Guenter1 at swisscom.com]

Hi,

we're using logback and the RollingFileAppender to write log files from several webservice to a /logs directory and automatically move "old" files into a /logs/archive directory based on a TimeBasedRollingPolicy. This works great with the following configuration:

    <appender name="SERVICE_CALL_SIFT" class="ch.qos.logback.classic.sift.SiftingAppender">
        <discriminator class="com.myproject.logback.ContextEnvironmentPartBasedDiscriminator">
            <DefaultValue>unknown</DefaultValue>
        </discriminator>
        <sift>
            <appender name="FILE-AUDIT-${environmentName}" class="ch.qos.logback.core.rolling.RollingFileAppender">
                <File>${LOG_DIR}/service_call_${environmentName}.log</File>
                <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
                    <!-- Rollover at midnight. Put log as uncompressed file to archive.  -->
                    <FileNamePattern>${LOG_DIR}/archive/service_call_${environmentName}_%d{yyyy-MM-dd}.log</FileNamePattern>
                    <!-- Keep 5 days worth of history -->
                    <MaxHistory>${MAX_HISTORY_DAYS}</MaxHistory>
                </rollingPolicy>

                <layout class="ch.qos.logback.classic.PatternLayout">
                    <Pattern>%d{HH:mm:ss.SSS} [%contextName] refId: %mdc{refId}, %msg%n</Pattern>
                </layout>
            </appender>
        </sift>
    </appender>

But since some of the log files are shared between different applications, I discovered some strange effects (one of the applications stopped writing into one of the log-files) and read about the prudent flag. Now, I tried to switch on the prudent mode using the following configuration:

    <appender name="SERVICE_CALL_SIFT" class="ch.qos.logback.classic.sift.SiftingAppender">
        <discriminator class="com.myproject.logback.ContextEnvironmentPartBasedDiscriminator">
            <DefaultValue>unknown</DefaultValue>
        </discriminator>
        <sift>
            <appender name="FILE-AUDIT-${environmentName}" class="ch.qos.logback.core.rolling.RollingFileAppender">
                <File>${LOG_DIR}/service_call_${environmentName}.log</File>
                <!-- Ensure safe writing to one log file from different contexts by setting prudent to true -->
                <Prudent>true</Prudent> 
                <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
                    <!-- Rollover at midnight. Put log as uncompressed file to archive.  -->
                    <FileNamePattern>${LOG_DIR}/archive/service_call_${environmentName}_%d{yyyy-MM-dd}.log</FileNamePattern>
                    <!-- Keep 5 days worth of history -->
                    <MaxHistory>${MAX_HISTORY_DAYS}</MaxHistory>
                </rollingPolicy>

                <layout class="ch.qos.logback.classic.PatternLayout">
                    <Pattern>%d{HH:mm:ss.SSS} [%contextName] refId: %mdc{refId}, %msg%n</Pattern>
                </layout>
            </appender>
        </sift>
    </appender>

This way, the node /appender/sift/appender/File isn't used anymore and the logger directly writes into the archive file specified under /appender/sift/appender/rollingPolicy/FileNamePattern.

Is there a way of using the prudent mode but still separating the log from the archive files?

Thanks for your help!
tom