How to add custom log appender to WSO2 products to directs logs to separate file(take mediator logs to different file)

Implement custom log appender class as follows.

package org.wso2.test.logging;
import org.apache.log4j.DailyRollingFileAppender;
import org.apache.log4j.spi.LoggingEvent;
import org.wso2.carbon.context.CarbonContext;
import org.wso2.carbon.utils.logging.LoggingUtils;
import org.wso2.carbon.utils.logging.TenantAwareLoggingEvent;
import java.io.File;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;
public class CustomAppender extends DailyRollingFileAppender {
    private static final String LOG_FILE_PATH = org.wso2.carbon.utils.CarbonUtils.getCarbonHome() + File.separator + "repository" +
                                                File.separator + "logs" + File.separator + "messages" + File.separator;
   
    @Override
    protected void subAppend(LoggingEvent loggingEvent) {
        int tenantId = AccessController.doPrivileged(new PrivilegedAction() {
            public Integer run() {
                return CarbonContext.getThreadLocalCarbonContext().getTenantId();
            }
        });
       
        String logFileName = "test_file";
            try {
                this.setFile(LOG_FILE_PATH + logFileName, this.fileAppend, this.bufferedIO, this.bufferSize);
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            String serviceName = CarbonContext.getThreadLocalCarbonContext().getApplicationName();
            final TenantAwareLoggingEvent tenantAwareLoggingEvent = LoggingUtils
                    .getTenantAwareLogEvent(loggingEvent, tenantId, serviceName);
            AccessController.doPrivileged(new PrivilegedAction() {
                public Void run() {
                    CustomAppender.super.subAppend(tenantAwareLoggingEvent);
                    return null; // nothing to return
                }
            });
        }
    }
}

Then add following to log4j.properties file.

log4j.logger.org.wso2.test.logging.LoggingClassMediator=INFO, NEW_CARBON_LOGFILE

log4j.appender.NEW_CARBON_LOGFILE=org.wso2.test.logging.CustomAppender
log4j.appender.NEW_CARBON_LOGFILE.File=${carbon.home}/repository/logs/${instance.log}/wso2carbon${instance.log}.log
#log4j.appender.NEW_CARBON_LOGFILE.Append=true
log4j.appender.NEW_CARBON_LOGFILE.layout=org.wso2.carbon.utils.logging.TenantAwarePatternLayout
log4j.appender.NEW_CARBON_LOGFILE.layout.ConversionPattern=TID: [%T] [%S] [%d] %P%5p {%c} - %x %m {%c}%n
log4j.appender.NEW_CARBON_LOGFILE.layout.TenantPattern=%U%@%D [%T] [%S]
log4j.appender.NEW_CARBON_LOGFILE.threshold=INFO
log4j.appender.NEW_CARBON_LOGFILE.MaxFileSize=5kb

Then add org.wso2.test.logging.LoggingClassMediator class to your mediation flow. Please see sample mediator code below.

package org.wso2.test.logging;
import org.apache.log4j.Logger;
import org.apache.synapse.MessageContext;
import org.apache.synapse.mediators.AbstractMediator;
public class LoggingClassMediator extends AbstractMediator {
private static final Logger log = Logger.getLogger(AVSLoggingClassMediator.class);
public LoggingClassMediator() {
}
public boolean mediate(MessageContext mc) {
String apiName = mc.getProperty("SYNAPSE_REST_API").toString();
String name = "APIName::" + apiName+"::";
try{
log.info(name+"LOGGING MESSAGE " + mc.getProperty("RESPONSE_TIME"));
log.info(name+"LOGGING MESSAGE " + mc.getProperty("SYNAPSE_REST_API"));
}catch(Exception e){
log.error(name+"ERROR :",e);
}
return true;
}