Apache Log4j is a well known framework for logging application behavior. Log4j 2 is an upgrade to Log4j that provides significant improvements over its predecessor, Log4j 1.x, and provides many of the improvements available in Logback while fixing some inherent problems in Logback's architecture.
This is the twelfth release and first release candidate of Log4j 2 and is being made available to encourage use and feedback from the community. Rapid feedback is especially critical at this point since a general availability release is on the horizon.
This release contains several changes that break binary and backwards compatibility with previous versions. Please read the release notes correctly so that you can adjust your usage of Log4j 2, if necessary.
o LOG4J2-530: (JMX) JMX Client GUI should dynamically update when LoggerContext MBeans are registered/unregistered in MBean server.
o LOG4J2-479: ThreadContext now uses plain ThreadLocal by default, unless system property isThreadContextMapInheritable has value "true". Thanks to MK.
o LOG4J2-481: Add Stream interface to Loggers. Thanks to Matt Sicker.
o LOG4J2-482: Documentation fix: The attribute of Route to refer to an appender is "ref" not "AppenderRef". Thanks to Hongdi Ren.
o LOG4J2-467: Added option to toggle Thread name caching in AsyncLogger. Thanks to Anthony Baldocchi.
o LOG4J2-423: Added MBeans for instrumenting AsyncAppenders and AsyncLogger RingBuffers, exposing queue size, remaining capacity and other attributes.
o LOG4J2-420: Create a lookup for resource bundle substitution.
o LOG4J2-415: Format log event time as UNIX time (seconds or milliseconds).
o LOG4J2-401: Configure FileAppender buffer size.
o LOG4J2-402: Configure RandomAccessFileAppender buffer size.
o LOG4J2-500: (JMX - ObjectNames changed!) Unloading one web application unloads JMX MBeans for all web applications.
o LOG4J2-531: Fixed bugs where rolled log files were overwritten by RollingFile appender with composite time and size based policies. Thanks to Geoff Ballinger.
o LOG4J2-475: Changed the MongoDBConnection to add a MongoDB encoding hook instead of a decoding hook. Thanks to Matt Sicker.
o LOG4J2-489: Fixed the JPAAppender's overuse of transactions by connecting (borrowing from pool) on new write internal or on flush.
o LOG4J2-457: Fixed failure of JDBC and JPA appender to properly release database connections by connecting (borrowing from pool) on new write internal or on flush.
o LOG4J2-442: Fixed problem with JDBC and JPA appender connectivity in WebSphere by connecting (borrowing from pool) on new write internal or on flush.
o LOG4J2-438: Ensured the JDBCAppender commits transactions after a single write or a flush of multiple writes.
o LOG4J2-407: Fixed inability to recover from lost database connection in database appenders by connecting (borrowing from pool) on new write internal or on flush.
o LOG4J2-511: Stop AsyncLoggerConfig Disruptor thread(s), then AsyncAppender thread(s) first before stopping other appenders. Thanks to James Pretorius.
o LOG4J2-392: Stop AsyncLoggerConfig Disruptor thread(s), then AsyncAppender thread(s) first before stopping other appenders. Thanks to ilynaf, Andre Bogus.
o LOG4J2-345: (OSGi) logging.log4j-1.2-api doesn't export the log4j API 1.2. Dependent bundles can not be resolved. Thanks to Roland Weiglhofer, Matt Sicker.
o LOG4J2-523: LocalizedMessage serialization is broken.
o LOG4J2-385: Fixed issues with time-based file rollover (monthly, weekly, hourly and every minute). Thanks to Ace Funk, Porfirio Partida.
o LOG4J2-452: Added a ServletContext attribute that, when set to "true", disables Log4j's auto-initialization in Servlet 3.0+ web applications.
o LOG4J2-512: Exposed Log4j web support interface and methods and the LoggerContext through ServletContext attributes so that threads not affected by filters (such as asynchronous threads) can utilize the LoggerContext. Also updated the Log4j filter so that it supports async. Thanks to Chandra Sekhar Kakarla, Matt Sicker.
o LOG4J2-409: Created a utility to properly escape backslashes before creating URIs, and changed URI creation to use the utility instead of instantiating URI directly. Thanks to Frank Steinmann, Thomas Neidhart.
o LOG4J2-344: Changed the Servlet 3.0 auto-initializer to add the filter by class to get around a WebLogic bug. Thanks to Keir Lawson, Tomasz Wladzinski.
o LOG4J2-359: Changed the Servlet 3.0 auto-initializer so that it does nothing in a Servlet 2.5 or older application. This ensures behavioral consistency across containers. This includes additional fixes to abort initialization if a duplicate filter already exists and to check the actual Servlet EFFECTIVE version. Thanks to Abhinav Shah.
o LOG4J2-517: Switch in log4j-1.2-api Category.getEffectiveLevel has no cases for FATAL, OFF.
o LOG4J2-406: (JMX) Unregister all log4j JMX MBeans when the LoggerContext is stopped to allow web application classes to be GC-ed on undeploy. Thanks to Kerrigan Joseph.
o LOG4J2-405: Configuration was being processed twice at startup.
o LOG4J2-398: Configure properties and setup Interpolator before processing rest of configuration.
o LOG4J2-470: hostName property was not being set until after the first configuration element.
o LOG4J2-464: Support arrays as sub-elements of a JSON configuration.
o LOG4J2-492: (JMX) Fixed MalformedObjectNameException if context name contains '=' or newline characters. Thanks to Shaddy Baddah, Herlani Junior.
o LOG4J2-377: (OSGi) Fix NPE during shutdown. Thanks to Roland Weiglhofer, Matt Sicker.
o LOG4J2-463: Fixed documentation for MyApp example application in the Automatic Configuration section Thanks to Michael Diamond, Matt Sicker.
o LOG4J2-408: Fixed error in documentation code example in manual/eventlogging.html Thanks to Dongqing Hu, Matt Sicker.
o LOG4J2-451: Fixed typo in documentation: system property should be log4j2.loggerContextFactory Thanks to Vinay Pothnis, Matt Sicker.
o LOG4J2-443: Fixed issue where log4j2 LoggerContext did not show up in JMX GUI or JConsole. Thanks to Colin Froggatt, Tudor Har.
o LOG4J2-485: Fixed issue where toString methods that perform logging could deadlock AsyncAppender.
o LOG4J2-445: ResolverUtil cannot find packages in file URLs which include the '+' character. Thanks to Anthony Baldocchi.
o LOG4J2-430: Use the formatted Message in RFC5424Layout for non-StructuredDataMessages. Thanks to David Gstir.
o LOG4J2-459: Set external context when constructing the LoggerContext.
o LOG4J2-466: Cannot load log4j2 config file if path contains plus '+' characters. Thanks to Jan Tepke.
o LOG4J2-462: Fix LogEvent to never return null Level, fixes LevelPatternConverter.format may throw NPE. Thanks to Daisuke Baba.
o LOG4J2-465: Fix LogEvent to never return null Level, fixes ThresholdFilter throws NPE. Thanks to Daisuke Baba.
o LOG4J2-471: Fixed issue where toString methods that perform logging could deadlock AsyncLogger. Thanks to Anthony Baldocchi.
o LOG4J2-455: RingBufferLogEvent should return Message timestamp for TimestampMessage messages. Thanks to Robin Zhang Tao.
o LOG4J2-477: NPE in ClassLoaderContextSelector. Thanks to Tal Liron.
o LOG4J2-454: TimeBasedTriggeringPolicy should use event time millis. Thanks to Robin Zhang Tao.
o LOG4J2-472: BaseConfiguration class does not properly implement Configuration interface. Thanks to Tal Liron.
o LOG4J2-447: XMLLayout does not include marker name. Thanks to Jeff Hudren, Mark Paluch, Scott Deboy.
o LOG4J2-323: Resolved memory leak by releasing reference to ThreadLocal when AsyncLogger is stopped.
o LOG4J2-425: Resolved memory leak by populating AsyncLoggerConfigHelper ring buffer via EventTranslatorTwoArg, eliminating the need for a ThreadLocal.
o LOG4J2-417: Fix Event Level / LoggerConfig Level table at the architecture documentation page.
o LOG4J2-404: <at> EnterpriseNumber" was missing in the ID of structured data when RFC5424Layout is used Thanks to Kamal Bahadur.
o LOG4J2-379: Fixed issue that prevented Log4J from working in Google App Engine.
o Renamed the org.apache.logging.log4j.core.appender.db.nosql.mongo package to org.apache.logging.log4j.core.appender.db.nosql.mongodb.
o Renamed the org.apache.logging.log4j.core.appender.db.nosql.couch package to org.apache.logging.log4j.core.appender.db.nosql.couchdb.
o LOG4J2-507: Space Level numbers by 100 instead of 1.
o LOG4J2-41: Add support for custom logging levels. Thanks to Nick Williams.
o LOG4J2-490: Update EasyMock to version 3.2. Thanks to Matt Sicker.
o LOG4J2-453: Update Flume Appender to use Flume 1.4.0.
o LOG4J2-528: Rename package org.apache.logging.log4j.core.appender.rolling.helper to org.apache.logging.log4j.core.appender.rolling.action.
o LOG4J2-532: Resource leak in Flume appender when it cannot create a BerkeleyDB db.
Apache Log4j 2.0-rc1 requires a minimum of Java 6 to build and run. Basic compatibility with Log4j 1.x is provided through the log4j-1.2-api component, however it does not implement some of the very implementation specific classes and methods. The package names and Maven group ID have been changed to org.apache.logging.log4j to avoid any conflicts with Log4j 1.x.
For complete information on Apache Log4j 2, including instructions on how to submit bug reports, patches, or suggestions for improvement, see the Apache Apache Log4j 2 website:http://logging.apache.org/log4j/2.x/
(Special thanks to all the PMC members who helped me complete my first (and rather rocky) release!)