Let’s break down what’s going wrong and fix your configuration step by step—this is a super common gotcha when setting up Log4J for the first time!

The Core Issue #

Your com.me.kafka logger is configured with DEBUG level and additivity=false, but you haven’t assigned any appenders to it. Since additivity=false disables inheriting appenders from the root logger, this logger has nowhere to send its logs—hence the warning.

Corrected Configuration #

Here’s the adjusted config that will route logs from both the root logger and your com.me.kafka package to the console and rolling file:

# Root logger: only FATAL and above go to appenders
log4j.rootCategory=FATAL, util_kafka_console, util_kafka_file

# com.me.kafka logger: DEBUG and above, uses both appenders, no inheritance from root
log4j.logger.com.me.kafka=DEBUG, util_kafka_console, util_kafka_file
log4j.additivity.com.me.kafka=false

# System properties (ensure these are passed via JVM args, or hardcode the path below)
# filename=please_specify_log_location.log
# my_kafka.logs.dir=log

# Console Appender
log4j.appender.util_kafka_console=org.apache.log4j.ConsoleAppender
log4j.appender.util_kafka_console.layout=org.apache.log4j.PatternLayout
log4j.appender.util_kafka_console.layout.ConversionPattern=[%p] %d{yyyy-MM-dd HH:mm:ss} %x %c [%M] (%L) - %m%n

# Rolling File Appender
log4j.appender.util_kafka_file=org.apache.log4j.RollingFileAppender
log4j.appender.util_kafka_file.layout=org.apache.log4j.PatternLayout
log4j.appender.util_kafka_file.layout.ConversionPattern=[%p] %d{yyyy-MM-dd HH:mm:ss} %x %c [%M] (%L) - %m%n
# Option 1: Use system properties (ensure JVM args like -Dfilename=kafka.log -Dmy_kafka.logs.dir=./logs are set)
log4j.appender.util_kafka_file.File=${my_kafka.logs.dir}/${filename}
# Option 2: Hardcode the path if you don't need dynamic variables
# log4j.appender.util_kafka_file.File=./logs/kafka_debug.log
log4j.appender.util_kafka_file.MaxFileSize=10MB
log4j.appender.util_kafka_file.MaxBackupIndex=2

Key Fixes Explained #

• Added appenders to com.me.kafka: By adding util_kafka_console, util_kafka_file to the logger definition, you’re telling Log4J exactly where to send logs from this package.
• Verified variable resolution: If you’re using the ${my_kafka.logs.dir} and ${filename} variables, make sure you pass them as JVM arguments when starting your application, e.g.:

  java -Dmy_kafka.logs.dir=./logs -Dfilename=kafka_app.log -jar your-app.jar
  

  If you don’t need dynamic paths, hardcoding the file path avoids any variable parsing issues.
• Cleaned up whitespace: Removed the extra tab in the conversion pattern (optional, but makes the config cleaner).

Additional Checks #

1. Ensure Log4J dependencies are correct: Make sure you have the right Log4J 1.x jars in your classpath (since you’re using org.apache.log4j.* classes).
2. Confirm config file location: Log4J looks for log4j.properties (or log4j.xml) in the root of your classpath by default. If you’re placing it elsewhere, specify the path with the JVM argument -Dlog4j.configuration=file:/path/to/your/log4j.properties.

内容的提问来源于stack exchange，提问作者Havnar