Logback project Ceki Gülcü & Sébastien Pennec

Logback project

• Ceki Gülcü & Sébastien Pennec

~

• No revolution, only evolution.

• log4j is no longer being actively developed

• The same basic plumbing only done better.

• Faster, smaller, higher gas mileage, and generally more bang for the buck.

Modular architecture

• logback-core

• Joran, Status,

• Context, pattern parsing

• logback-classic

• developer logging

• logback-access

• container (access) logging

Access Logging

• Definition: Access log

• The log generated when a user accesses a web-page on a web server.

• Logback-access integrates seamlessly with Jetty and Tomcat

logback-classic implements SLF4J

• Logback offers a native implementation of the SLF4J API => Logback exposes its logging API through SLF4J.

• If you are using logback, you are actually using SLF4J

• SLF4J can delegate to log4j, logback, java.util.logging or JCL

• SLF4J can bridge log4j, JCL and j.u.l.

Joran: a bowl of fresh air

• Given rules (patterns & actions) it can configure any object.

• Joran can learn new rules on the fly.

• With its implicit rules, you don’t even have to write rules.

• It can do partial replay.

• It is generic (can be used in your own projects)

Configuration example:

• >

• logFile.log

• >

• logFile.%d{yyyy-MM-dd}.log.zip

• 
  

• %d{HH:mm:ss,SSS} [%thread] %-5level %logger{22} - %msg%n

• 
  

Logback-access configuration

• >

• access.log"

• >

• access.%d{yyyy-MM-dd}.log.zip

• 
  combined
  

Another example:

• 
  5 minutes
  

• object for each run of the test -->

• jndi://com.wombat/ds"

• 
  60 seconds
  

• c:/wombat/foo.properties

Is Joran for me?

• Joran is ideal for building frameworks which need to support arbitrary user-developed plug-ins.

Internal error reporting

• Who shall guard the guards?

• Logback modules cannot use logging to report their own state.

• Something more generic is needed.

Errors in action

• Internal state available via StatusManager

• Exceptions and status messages accompanied by references, i.e. URLs, to external documents

JMX

• Logback configuration can be reloaded via JMX

• Statistical results exposed via JMX

Documentation

• Major area of effort.

• Complete manual, with over 150 pages of documentation, is available for free

• A short introduction to access logging with logback-access and Jetty

• javadoc, FAQ, error codes,…

Filters, Filters. Filters everywhere

• Filters attachable to any Appender

• Evaluator filters

• Janino filters for evaluation based on java expressions

• TurboFilters for optimized global processing

EvaluatorFilter & Janino

• >

• logger.contains("LoggingTask") &&

• message.contains("Howdydy-diddly-ho") &&

• (timeStamp-loggerContext.getBirthTime()) >= 20000

• DENY

• 512

TurboFilters

• >

• userid

• sebastien

• ACCEPT

Parameterized logging

• Integer entry = new Interger(50);

• logger.debug("The entry is "+entry+".");

• can be optimized as:

• if(logger.isDebugEnabled()) {

• logger.debug("The entry is "+entry+".");

• }

• or better yet:

• logger.debug("The entry is {}.", entry);

Markers for specialized handling

• Markers are metadata for logging statements, coloring them for specialized processing

SiftingAppender or the appender-making appender

• Sift logging according to runtime attributes

• E.g. separate logs according to user sessions, so that the log file generated by every user go into distinct log files, one log file per user.

• Works with any appender, not just FileAppender

SiftingAppender (continued)

• userid

• unknown

• >

• >${userid}.logs

• false

• 
  %d %level %mdc %logger - %msg%n
  

Tested & Ready

• Battery of over 450 unit tests

• Tests written concomitantly with the code

Package versions in stack traces

• java.lang.NullPointerException

• at com.xyz.Wombat(Wombat.java:57) ~[wombat-1.3.jar:1.3]

• at com.xyz.Wombat(Wombat.java:76) ~[wombat-1.3.jar:1.3]

• at sun.reflect.NativeMethodAccessorImpl.invoke0(Native) ~[na:1.5.0_06]

• at java.lang.reflect.Method.invoke(Method.java:585) ~[na:1.5.0_06]

• at junit.runners.TestMethod.invoke(TestMethod.java:59) [junit-4.4.jar:na]

• etc..

logger name abbreviation

Odds and ends

• RollingFileAppender automatic file compression the background

• FileAppender and RollingFileAppender allow for the same log file to be written to by instances located in different JVMs

• 10 fold improvement in the speed of transporting logging events over the wire

• SMTPAppender now does TLS and SSL, subject line in outgoing email now based on PatternLayout

Odds and ends II

• %() in pattern strings can do magic

• %-50(%d %level [%thread]) - %m%n

• DuplicateMessage filter

Odds and ends II

• %() in pattern strings can do magic

• %-50(%d %level [%thread]) - %m%n

• DuplicateMessage filter

Plans for the near future

• Finer threading model leading to less contention

• Better documentation

• Eclipse plug-in to visualize your logs

Conclusion

• Logback is the unofficial successor of log4j, as the latter is no longer being actively developed.

Questions?

• read the docs at http://logback.qos.ch/

• study the code at http://svn.qos.ch

• write to us at [e-mail]

• file a bug report at http://jira.qos.ch/

• chat with us at irc.freenode.net#qos

• talk to us at [phone]