log4j.xml configuration with <rollingPolicy> and <triggeringPolicy>

Question

I try to configure log4j.xml in such a way that file will be rolled upon file size, and the rolled file's name will be i.e: "C:/temp/test/test_log4j-%d{yyyy-MM-dd-HH_mm_ss}.log" I followed this discussion: http://web.archiveorange.com/archive/v/NUYyjJipzkDOS3reRiMz

Finally it worked for me only when I add:

try {
   Thread.sleep(1);
  } catch (InterruptedException e) {
   e.printStackTrace();
  }

to the method:

public boolean isTriggeringEvent(Appender appender, LoggingEvent event,
            String filename, long fileLength)  

which make it works.

The question is if there is a better way to make it work? since this method call many times and slow my program.

Here is the code:

package com.mypack.rolling;

import org.apache.log4j.rolling.RollingPolicy;
import org.apache.log4j.rolling.RolloverDescription;
import org.apache.log4j.rolling.TimeBasedRollingPolicy;

/**
 * Same as org.apache.log4j.rolling.TimeBasedRollingPolicy but acts only as
 * RollingPolicy and NOT as TriggeringPolicy.
 *
 * This allows us to combine this class with a size-based triggering policy
 * (decision to roll based on size, name of rolled files based on time)
 *
 */
public class CustomTimeBasedRollingPolicy implements RollingPolicy {

 TimeBasedRollingPolicy timeBasedRollingPolicy = new TimeBasedRollingPolicy();

 /**
  * Set file name pattern.
  * @param fnp file name pattern.
  */
 public void setFileNamePattern(String fnp) {
  timeBasedRollingPolicy.setFileNamePattern(fnp);
 }
 /*
 public void setActiveFileName(String fnp) {
  timeBasedRollingPolicy.setActiveFileName(fnp);
 }*/

 /**
  * Get file name pattern.
  * @return file name pattern.
  */
 public String getFileNamePattern() {
  return timeBasedRollingPolicy.getFileNamePattern();
 }

 public RolloverDescription initialize(String file, boolean append) throws SecurityException {
  return timeBasedRollingPolicy.initialize(file, append);
 }

 public RolloverDescription rollover(String activeFile) throws SecurityException {
  return timeBasedRollingPolicy.rollover(activeFile);
 }

 public void activateOptions() {
  timeBasedRollingPolicy.activateOptions();
 }
}



package com.mypack.rolling;

import org.apache.log4j.helpers.OptionConverter;
import org.apache.log4j.Appender;
import org.apache.log4j.rolling.TriggeringPolicy;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.spi.OptionHandler;

/**
 * Copy of org.apache.log4j.rolling.SizeBasedTriggeringPolicy but able to accept
 * a human-friendly value for maximumFileSize, eg. "10MB"
 * 
 * Note that sub-classing SizeBasedTriggeringPolicy is not possible because that
 * class is final
 */
public class CustomSizeBasedTriggeringPolicy implements TriggeringPolicy, OptionHandler {

 /**
  * Rollover threshold size in bytes.
  */
 private long maximumFileSize = 10 * 1024 * 1024; // let 10 MB the default max size

 /**
  * Set the maximum size that the output file is allowed to reach before
  * being rolled over to backup files.
  * 
  * <p>
  * In configuration files, the <b>MaxFileSize</b> option takes an long
  * integer in the range 0 - 2^63. You can specify the value with the
  * suffixes "KB", "MB" or "GB" so that the integer is interpreted being
  * expressed respectively in kilobytes, megabytes or gigabytes. For example,
  * the value "10KB" will be interpreted as 10240.
  * 
  * @param value
  *            the maximum size that the output file is allowed to reach
  */
 public void setMaxFileSize(String value) {
  maximumFileSize = OptionConverter.toFileSize(value, maximumFileSize + 1);
 }

 public long getMaximumFileSize() {
  return maximumFileSize;
 }

 public void setMaximumFileSize(long maximumFileSize) {
  this.maximumFileSize = maximumFileSize;
 }

 public void activateOptions() {
 }

 public boolean isTriggeringEvent(Appender appender, LoggingEvent event,
            String filename, long fileLength) {
  try {
   Thread.sleep(1);
  } catch (InterruptedException e) {
   e.printStackTrace();
  }

  boolean result = (fileLength >= maximumFileSize);

  return result;
 }

}

and the log4j.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="true">
 <appender name="console" class="org.apache.log4j.ConsoleAppender">
  <param name="Target" value="System.out" />
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="%d [%t] %-5p %c -> %m%n" />
  </layout>
 </appender>

 <appender name="FILE" class="org.apache.log4j.rolling.RollingFileAppender">
  <param name="file" value="C:/temp/test/test_log4j.log" />
  <rollingPolicy class="com.mypack.rolling.CustomTimeBasedRollingPolicy">
   <param name="fileNamePattern" value="C:/temp/test/test_log4j-%d{yyyy-MM-dd-HH_mm_ss}.log" />
  </rollingPolicy>
  <triggeringPolicy class="com.mypack.rolling.CustomSizeBasedTriggeringPolicy">
   <param name="MaxFileSize" value="200KB" />
  </triggeringPolicy>
  <layout class="org.apache.log4j.PatternLayout">
   <param name="ConversionPattern" value="%d [%t] %-5p %c -> %m%n" />
  </layout>
 </appender>

 <logger name="com.mypack.myrun" additivity="false">
  <level value="debug" />
  <appender-ref ref="FILE" />
 </logger>

 <root>
  <priority value="debug" />
  <appender-ref ref="console" />
 </root>

</log4j:configuration>

Answer 1

If you add debug output to the method, you will see that the method is called very often, even after the trigger has already fired, but the file size is still growing larger than the maximum file size.

I assume that the rolling behavior has some kind of buffer which is emptied before the actual (synchronous?) rollover takes place.

I think it has something to do with the fileNamePattern in the com.mypack.rolling.CustomTimeBasedRollingPolicy. As long as the 'second' in the filename does not change, the CustomSizeBasedTriggeringPolicy.isTriggeringEvent method is continously called with amounts larger than the maximum file size.