Logback project

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Logback project

• Ceki Gülcü Sébastien Pennec

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• 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.

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Modular architecture

• logback-core
• Joran, Status,
• Context, pattern parsing
• logback-classic
• developer logging
• logback-access
• container (access) logging

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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

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logback-classic implements SLF4J

• Logback offers a native implementation of the
  SLF4J API gt 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.

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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 dont even have to
  write rules.
• It can do partial replay.
• It is generic (can be used in your own projects)

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Configuration example

• ltappender name"FILE"
• class"ch.qos.logback.core.rolling.RollingFil
  eAppender"gt
• ltFilegtlogFile.loglt/Filegt
• ltrollingPolicy
• class"ch.qos.logback.core.rolling.TimeBasedRo
  llingPolicy"gt
• ltFileNamePatterngt
• logFile.dyyyy-MM-dd.log.zip
• lt/FileNamePattergt
• lt/rollingPolicygt
• ltlayout class"ch.qos.logback.classic.PatternLay
  out"gt
• ltPatterngt
• dHHmmss,SSS thread -5level
  logger22 - msgn
• lt/Patterngt
• lt/layoutgt
• lt/appendergt

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Logback-access configuration

• ltappender name"FILE"
• class"c.q.l.c.r.RollingFileAppender"gt
  
• ltFilegtaccess.log"lt/Filegt
• ltrollingPolicy
• class"c.q.l.c.r.TimeBasedRollingPolicy"gt
• ltFileNamePatterngt
• access.dyyyy-MM-dd.log.zip
• lt/FileNamePatterngt
• lt/rollingPolicygt
• ltlayout class"c.q.l.access.PatternLayout"gt
• ltPattern"gtcombinedlt/Pattern"gt
• lt/layoutgt
• lt/appendergt

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Another example

• lttestShell name"test1"gt
• ltperiodgt5 minuteslt/periodgt
• lt!-- we need to configure a totally new test
• object for each run of the test --gt
• lttest class"com.wombat.myTest"gt
• ltDataSource class"c.w.JNDIDS"gt
• lturlgtjndi//com.wombat/ds"lt/urlgt
• lt/DataSourcegt
• lt/testgt
• lttestShellgt
• lttestShell name"test2"gt
• ltperiodgt60 secondslt/periodgt
• lttest class"com.wombat.myTest2"gt
• ltfilegtc/wombat/foo.propertieslt/filegt
• lt/testgt
• lt/testShellgt

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Is Joran for me?

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

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Internal error reporting

• Who shall guard the guards?
• Logback modules cannot use logging to report
  their own state.
• Something more generic is needed.

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Errors in action

• Internal state available via StatusManager
• Exceptions and status messages accompanied by
  references, i.e. URLs, to external documents

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JMX

• Logback configuration can be reloaded via JMX
• Statistical results exposed via JMX

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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,

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Filters, Filters. Filters everywhere

• Filters attachable to any Appender
• Evaluator filters
• Janino filters for evaluation based on java
  expressions
• TurboFilters for optimized global processing

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EvaluatorFilter Janino

• ltappender name"CYCLIC"
• class"c.q.l.core.read.CyclicBufferAppen
  der"gt
• ltfilter class"c.q.l.core.filter.EvaluatorFilter
  "gt
• ltevaluator name"loggingTaskEval"gt
• ltexpressiongt
• logger.contains("LoggingTask")
• message.contains("Howdydy-diddly-ho")
• (timeStamp-loggerContext.getBirthTime())
  gt 20000
• lt/expressiongt
• lt/evaluatorgt
• ltOnMatchgtDENYlt/OnMatchgt
• lt/filtergt
• ltMaxSizegt512lt/MaxSizegt
• lt/appendergt

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TurboFilters

• ltturboFilter
• class"c.q.l.classic.turbo.MDCFilter"gt
• ltMDCKeygtuseridlt/MDCKeygt
• ltValuegtsebastienlt/Valuegt
• ltOnMatchgtACCEPTlt/OnMatchgt
• lt/turboFiltergt

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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)

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Markers for specialized handling

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

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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

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SiftingAppender (continued)

• ltappender name"SIFT" class"ch.qos.logback.class
  ic.sift.SiftingAppender"gt
• ltdiscriminatorgt
• ltKeygtuseridlt/Keygt
• ltDefaultValuegtunknownlt/DefaultValuegt
• lt/discriminatorgt
• ltsiftgt
• ltappender name"FILE-userid" 
• class"ch.qos.logback.core.FileApp
  ender"gt
• ltFilegtuserid.loglt/Filegts
• ltAppendgtfalselt/Appendgt
• ltlayoutgt
• ltPatterngtd level mdc logger -
  msgnlt/Patterngt
• lt/layoutgt
• lt/appendergt
• lt/siftgt
• lt/appendergt

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Tested Ready

• Battery of over 450 unit tests
• Tests written concomitantly with the code

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Package versions in stack traces

• java.lang.NullPointerException
• at com.xyz.Wombat(Wombat.java57)
  wombat-1.3.jar1.3
• at com.xyz.Wombat(Wombat.java76)
  wombat-1.3.jar1.3
• at sun.reflect.NativeMethodAccessorImpl.invoke0(N
  ative) na1.5.0_06
• at java.lang.reflect.Method.invoke(Method.java58
  5) na1.5.0_06
• at junit.runners.TestMethod.invoke(TestMethod.jav
  a59) junit-4.4.jarna
• etc..

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logger name abbreviation
Conversion specifier Displayed logger name
logger mainPackage.sub.sample.Bar
logger15 m.s.sample.Bar
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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

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Odds and ends II

• () in pattern strings can do magic
• -50(d level thread) - mn
• DuplicateMessage filter

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Odds and ends II

• () in pattern strings can do magic
• -50(d level thread) - mn
• DuplicateMessage filter

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Plans for the near future

• Finer threading model leading to less contention
• Better documentation
• Eclipse plug-in to visualize your logs

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Conclusion

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

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Questions?

• read the docs at http//logback.qos.ch/
• study the code at http//svn.qos.ch
• write to us at logback-user_at_qos.ch
• file a bug report at http//jira.qos.ch/
• chat with us at irc.freenode.netqos
• talk to us at 41 21 312 32 26