Major Description
When started as a regular java application, ie. java -jar, avro-tools displays an annoying log4j warning:
$ java -jar target/avro-tools-1.9.0-SNAPSHOT.jar tojson ./target/mapred/in/lines.avro/ log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory). log4j:WARN Please initialize the log4j system properly. log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
log4j should be properly initialized in the two supported execution contexts: regular jar & hadoop jar.
When run as a regular jar, log4j looks for a log4j.properties or log4j.xml in the classpath and displays the aforementioned warning message if none is found. IMHO, we should provide a default configuration file. User will still be able to override the log4j configuration using -Dlog4j.configuration.
When run with hadoop jar, hadoop-config.sh puts HADOOP_CONF_DIR first in the classpath. Since HADOOP_CONF_DIR contains a log4j.properties, the one provided by avro-tools won't be used, which seems fine. Here again, users can use -Dlog4j.configuration if they need.
What do you think of adding a simple log4j.properties file into src/main/resources ? What would be a good default log4j configuration ?