Spring boot multiple log files

Question

In my Spring boot project with "@Slf4j" annotated classes, for certain classes I want to log to a different file. But couldn't figure out how to do that. I have one logback-spring.xml file, which is referenced from my properties file like this:

logging.config= path/to/logback-spring.xml
logging.file=myCurrentLogFile.log

Do I have to create another logback-spring.xml file now? or I can configure it in current file, and if then how can I choose which logger to use when.

Answer 1

Just add another logger and appender. For example I used the following logback.xml

<property name="LOGS_HOME" value="/var/applications/myProject/applogs/" />

<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <layout class="ch.qos.logback.classic.PatternLayout">
        <Pattern>
            %d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n
        </Pattern>
    </layout>
</appender>

<appender name="FILE"
    class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${LOGS_HOME}myProject_log.log</file>
    <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
        <Pattern>
            %d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n
        </Pattern>
    </encoder>

    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
        <!-- rollover daily -->
        <fileNamePattern>${LOGS_HOME}myProject_log.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
        <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
            <maxFileSize>100MB</maxFileSize>
        </timeBasedFileNamingAndTriggeringPolicy>
    </rollingPolicy>
</appender>

<appender name="FILE-AUDIT" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${LOGS_HOME}myProject_audit.log</file>
    <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
        <Pattern>
            %d{yyyy-MM-dd HH:mm:ss};%msg%n
        </Pattern>
    </encoder>

    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
        <!-- rollover daily -->
        <fileNamePattern>${LOGS_HOME}myProject_audit.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
        <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
            <maxFileSize>100MB</maxFileSize>
        </timeBasedFileNamingAndTriggeringPolicy>
    </rollingPolicy>
</appender>

<logger name="com.myCompany.myProject" level="info" additivity="false">
    <appender-ref ref="FILE" />
    <appender-ref ref="STDOUT" />
</logger>

<logger name="audit-log" level="info" additivity="false">
    <appender-ref ref="FILE-AUDIT" />
    <appender-ref ref="STDOUT" />
</logger>

<root level="error">
    <appender-ref ref="FILE" />
    <appender-ref ref="STDOUT" />
</root>

In the code you can access the logger with:

private static Logger audit = LoggerFactory.getLogger("audit-log");

This will get the audit-log logger and use FILE-AUDIT appender.

The "standart" appender is used with any class that is in the specified package:

private static Logger logger = LoggerFactory.getLogger(MyApplication.class);

This will use the <logger name="com.myCompany.myProject" level="info" additivity="false"> and obviosly the FILE appender.