Creating multiple log files of different content with log4j

Question

Is there a way to configure log4j so that it outputs different levels of logging to different appenders  I m trying to set up multiple log files   The main log file would catch all INFO and above messages for all classes    In development  it would catch all DEBUG and above messages  and TRACE for specific classes   Then  I would like to have a separate log file   That log file would catch all DEBUG messages for a specific subset of classes  and ignore all messages for any other class  Is there a way to get what I m after

User · Answer

This should get you started   log4j rootLogger QuietAppender  LoudAppender  TRACE   setup A1 log4j appender QuietAppender org apache log4j RollingFileAppender log4j appender QuietAppender Threshold INFO log4j appender QuietAppender File quiet log         setup A2 log4j appender LoudAppender org apache log4j RollingFileAppender log4j appender LoudAppender Threshold DEBUG log4j appender LoudAppender File loud log      log4j logger com yourpackage yourclazz TRACE

User · Answer

I had this question  but with a twist - I was trying to log different content to different files   I had information for a LowLevel debug log  and a HighLevel user log   I wanted the LowLevel to go to only one file  and the HighLevel to go to both a file  and a syslogd   My solution was to configure the 3 appenders  and then setup the logging like this   log4j threshold ALL log4j rootLogger  LowLogger  log4j logger HighLevel ALL Syslog HighLogger log4j additivity HighLevel false   The part that was difficult for me to figure out was that the  log4j logger  could have multiple appenders listed  I was trying to do it one line at a time   Hope this helps someone at some point

User · Answer

Demo link  https   github com RazvanSebastian spring multiple log files demo git  My solution is based on XML configuration using spring-boot-starter-log4j  The example is a basic example using spring-boot-starter and the two Loggers writes into different log files

User · Answer

For the main logfile appender  set up a  Threshold   INFO to limit what is actually logged in the appender to INFO and above  regardless of whether or not the loggers have DEBUG  TRACE  etc  enabled   As for catching DEBUG and nothing above that    you d probably have to write a custom appender   However I d recommend not doing this  as it sounds like it would make troubleshooting and analysis pretty hard     If your goal is to have a single file where you can look to troubleshoot something  then spanning your log data across different files will be annoying - unless you have a very regimented logging policy  you ll likely need content from both DEBUG and INFO to be able to trace execution of the problematic code effectively  By still logging all of your debug messages  you are losing any performance gains you usually get in a production system by turning the logging  way  down

User · Answer

Perhaps something like this    lt  DOCTYPE log4j configuration SYSTEM  log4j dtd  gt   lt log4j configuration xmlns log4j  http   jakarta apache org log4j   gt    lt  -- general application log -- gt    lt appender name  MainLogFile  class  org apache log4j FileAppender  gt     lt param name  File  value  server log    gt     lt param name  Threshold  value  INFO    gt     lt layout class  org apache log4j PatternLayout  gt      lt param name  ConversionPattern  value   -5p  t   -40 40c   x -  m n   gt     lt  layout gt    lt  appender gt     lt  -- additional fooSystem logging -- gt    lt appender name  FooLogFile  class  org apache log4j FileAppender  gt     lt param name  File  value  foo log    gt     lt layout class  org apache log4j PatternLayout  gt      lt param name  ConversionPattern  value   -5p  t   -40 40c   x -  m n   gt     lt  layout gt    lt  appender gt    lt  -- foo logging -- gt    lt logger name  com example foo  gt     lt level value  DEBUG   gt     lt appender-ref ref  FooLogFile   gt    lt  logger gt    lt  -- default logging -- gt    lt root gt     lt level value  INFO   gt     lt appender-ref ref  MainLogFile   gt    lt  root gt   lt  log4j configuration gt    Thus  all info messages are written to server log  by contrast  foo log contains only com example foo messages  including debug-level messages

[java] Creating multiple log files of different content with log4j

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