Logback - how to get each logger logging to a separate log file?

Question

My application has lots of EJBs. The current bespoke Logger implementation creates a logger like this;

private static Logger logger = Logger.getInstance("SERVICE_NAME");

, and the logging will go into a file;

(path)/SERVICE_NAME/SERVICE_NAME.log

I want to replicate this behaviour with logback, but having real trouble grabbing the 'logger' name in the logback.xml configuration. It can be seen in the log encoder.pattern, i.e. "%d %-5level %logger{35} - %msg %n".

Any ideas how I can get this into a property/variable and then use it in the element?

Answer 1

I have a partial solution. If I create my own Discriminator, I can then use the Discriminator in the logback.xml to implement seperate-log-files-per-EJB.

Discriminator;

public class LoggerNameBasedDiscriminator implements Discriminator<ILoggingEvent> {

private static final String KEY = "loggerName";

private boolean started;

@Override
public String getDiscriminatingValue(ILoggingEvent iLoggingEvent) {
    return iLoggingEvent.getLoggerName();
}

@Override
public String getKey() {
    return KEY;
}

public void start() {
    started = true;
}

public void stop() {
    started = false;
}

public boolean isStarted() {
    return started;
}

}

Then my logback.xml;

    <configuration debug="true" scan="true" scanPeriod="30 seconds">

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
        <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg</pattern>
    </encoder>
    </appender>

  <appender name="SIFT" class="ch.qos.logback.classic.sift.SiftingAppender">
    <discriminator class="package.to.LoggerNameBasedDiscriminator"/>
     <sift>
      <appender name="FILE-${loggerName}" class="ch.qos.logback.core.FileAppender">
    <FILE>path/to/logs/${loggerName}/${loggerName}.log</FILE>
    <encoder>
      <pattern>%d{HH:mm:ss.SSS} %-50(%level %logger{35}) %msg%n</pattern>
     </encoder>
      </appender>
     </sift>
    </appender>

    <root level="debug">
    <appender-ref ref="STDOUT" />
    <appender-ref ref="SIFT" />
    </root>
</configuration>

This solution seems to work, but now I have no time or size based log rotation!

Answer 2

Thanks to your example I implemented a solution for a loggername-based discriminator which routes different logger output to different files. Although the documentation of logback is so verbose, I couldn't find this essential information. You've surely found the solution mentioned by yayitswei already.

logback.xml:

[...]
<timestamp key="startTimestamp" datePattern="yyyy-MM-dd"/>
<timestamp key="folderTimestamp" datePattern="MM-yyyy"/>

<property name="LOGDIR" value="/var/log/spock" />

<appender name="SIFT" class="ch.qos.logback.classic.sift.SiftingAppender">
    <discriminator class="com.enterprise.spock.LoggerNameBasedDiscriminator" />
    <sift>
        <appender name="FILE-${loggerName}" class="ch.qos.logback.core.rolling.RollingFileAppender">
            <file>${LOGDIR}/${loggerName}-${startTimestamp}.log</file>
            <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
                <fileNamePattern>${LOGDIR}/${folderTimestamp}/${loggerName}-%d{yyyy-MM-dd}-%i.log.gz</fileNamePattern>
                <maxFileSize>500KB</maxFileSize>
                <maxHistory>100</maxHistory>
                <totalSizeCap>50MB</totalSizeCap>
            </rollingPolicy>
            <encoder>
                <charset>UTF-8</charset>
                <pattern>%level %date{HH:mm:ss.SSS}: %msg %n</pattern>
            </encoder>
        </appender>
    </sift>
</appender>
[...]

Edit: I replaced TimeBasedRollingPolicy with SizeAndTimeBasedRollingPolicy as proposed here. You'll need at least logback 1.1.7 for that.

What you get with this, is a logfile for each Logger created. Every logfile will look like this: /var/log/loggername-2017-08-03.log.

When about 500KB was written to the file, it will be archived as a gz-zipfile into /var/log/loggername/08-2017/loggername-2017-08-03-0.log.gz.

The 0 at the end of the gz-zipfile-name is the %i from the <fileNamePattern> above. Without the %i it won't work. Remember to use <configuration debug=true> in logback.xml if something won't work.