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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-coreJoran, Status,

Context, pattern parsing logback-classic

developer logging logback-access

container (access) logging

id Components

logback-core

logback-classic logback-access

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Access Logging

Definition: Access logThe 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 => 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 don’t 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:

<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender"> <File>logFile.log</File> <rollingPolicy

class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"> <FileNamePattern> logFile.%d{yyyy-MM-dd}.log.zip </FileNamePatter> </rollingPolicy>

<layout class="ch.qos.logback.classic.PatternLayout"> <Pattern> %d{HH:mm:ss,SSS} [%thread] %-5level %logger{22} - %msg%n </Pattern> </layout></appender>

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Logback-access configuration<appender name="FILE" class="c.q.l.c.r.RollingFileAppender"> <File>access.log"</File> <rollingPolicy class="c.q.l.c.r.TimeBasedRollingPolicy"> <FileNamePattern> access.%d{yyyy-MM-dd}.log.zip </FileNamePattern> </rollingPolicy>

<layout class="c.q.l.access.PatternLayout"> <Pattern">combined</Pattern"> </layout></appender>

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Another example:<testShell name="test1"> <period>5 minutes</period> <!-- we need to configure a totally new test object for each run of the test --> <test class="com.wombat.myTest"> <DataSource class="c.w.JNDIDS"> <url>jndi://com.wombat/ds"</url> </DataSource> </test><testShell>

<testShell name="test2"> <period>60 seconds</period> <test class="com.wombat.myTest2"> <file>c:/wombat/foo.properties</file> </test></testShell>

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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<appender name="CYCLIC" class="c.q.l.core.read.CyclicBufferAppender"> <filter class="c.q.l.core.filter.EvaluatorFilter"> <evaluator name="loggingTaskEval">

<expression> logger.contains("LoggingTask") &&

message.contains("Howdydy-diddly-ho") && (timeStamp-loggerContext.getBirthTime()) >= 20000

</expression> </evaluator> <OnMatch>DENY</OnMatch>

</filter> <MaxSize>512</MaxSize></appender>

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TurboFilters<turboFilter class="c.q.l.classic.turbo.MDCFilter">

<MDCKey>userid</MDCKey>

<Value>sebastien</Value>

<OnMatch>ACCEPT</OnMatch>

</turboFilter>

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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) <appender name="SIFT"

class="ch.qos.logback.classic.sift.SiftingAppender"> <discriminator> <Key>userid</Key> <DefaultValue>unknown</DefaultValue> </discriminator> <sift> <appender name="FILE-${userid}"  class="ch.qos.logback.core.FileAppender"> <File>${userid}.log</File>s <Append>false</Append> <layout> <Pattern>%d %level %mdc %logger - %msg%n</Pattern> </layout> </appender> </sift> </appender>

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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.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..

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logger name abbreviation

Conversion specifier

Displayed logger name

%logger mainPackage.sub.sample.Bar

%logger{15} 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]) - %m%n DuplicateMessage filter

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Odds and ends II

%() in pattern strings can do magic

%-50(%d %level [%thread]) - %m%n 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@qos.ch file a bug report at http://jira.qos.ch/ chat with us at irc.freenode.net#qos talk to us at +41 21 312 32 26