• http://logging.apache.org/log4j/
• Build Flexible Logs With log4j - O'Reilly Media : Log4j 기본을 잘 설명하고 있다.
• Log4j 로그 패턴
• Log4j JDBCAppender
• Log4j XML 설정
• ChainSaw Log4j의 로그를 Socket으로 받아서 보여준다.
• LogDigger FireFox에서 log4j 로그를 본다.
• Stat4j

• 중복으로 로그가 쌓인다면, 로거에 additivity 속성을 false로 지정한다.

• Asynchronous logging with log4j
• AsyncAppender
• log4j AsyncAppender 사용시 유의사항
  • convertion pattern에서 %F:%L 사용시 ?:? 로 발생할 수 있다.
  • <param name=“locationInfo” value=“true”/> 를 추가해야 한다.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd" >
<log4j:configuration>
    <appender name="stdout" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%d{yyyy/MM/dd HH:mm:ss,SSS} [%t] %-5p %c %x - %m%n"/>
        </layout>
    </appender>
    <appender name="ASYNC" class="org.apache.log4j.AsyncAppender">
        <param name="BufferSize" value="500"/>
        <appender-ref ref="stdout"/>
    </appender>
    <root>
        <priority value="error"></priority>
        <appender-ref ref="ASYNC"/>
    </root>
</log4j:configuration>

• 주의 할 점들
  • If you see duplicated entries on your log, make sure your logger has the additivity attribute set to false.
  • The BufferSize parameter of the AsyncAppender defines the number of entries that will be stored in memory to let the actual appender catch up flushing them to their final destination. If this buffer fills up, the logging will switch to a synchronous mode until buffer space becomes available, potentially becoming a performance issue. Make sure this buffer is big enough, taking into account the IO speed and number of log entries generated by your application.
  • You can add the Blocking parameter to the AsyncAppender definition in your config file, if you set it to false (the default value is true) when the buffer fills up, the appender will discard log events until new buffer space becomes available. This can be unacceptable in applications where logging information is critical, but on the other hand can be very desirable where performance is a critical factor.