The document discusses the importance and challenges of application logging for software engineers, detailing what logs are, who uses them, and their purposes in various contexts like debugging and performance monitoring. It outlines guidelines for effective logging practices, emphasizing clarity and context in log records while addressing common pitfalls and examples of ineffective logging. Additionally, it covers specific logging frameworks and the growing significance of standardized logging in modern software applications.

2. APPLICATION LOGGING

3. About MESander De VosSoftware EngineerRealDolmen 2008Past projectsMaTMa (M*)E-Metro (FOD-ECO)SP10B (FOD-FIN)MIK (FOD-MOB)

4. QuotesFrom The Field“Whoneeds logs? Isuredon’t!”“Debugger is better! Sysoutworkstoo!”“Isn’tthatwhatinfrastructure does?”“It slows down disk and memory!”“It isn’t in the spec!”“We don’tknowwhatto log – we’lljust log something!”“We don’tknowhow – we’lljust do itsomehow!”

5. AgendaWhat is loggingDefinition andChallengesWhyloggingWhouses logsWhat logs are usedforFunctional or non-functionalWhatto logWhatwill (not) help youLog messagedecomposedGuidelinesHow to log in JavaLogging in productionLog processing and analysis

6. What is logging

7. Definition“Logs are the recordings of one or more events occurring on information systems.”“Logs can be organized based on the program, day, severity, host, or a number of other categories.““Logs may be referred to as log files, audit logs, or audit trails.Logs also cover alerts, alarms and event records.“

8. Log challengesDecentralizationCloudSOAVolatilityMultiple tiersandlayersArchivalAccessabilityAbsence of critical informationRandom log formats

9. WHY logging

10. Whouses logsManaged ServicesSecurity TeamsMonitorDetectInvestigateTrackAnalyzeAuditorsDevelopersDebuggingCustomer

11. What logs are usedforDebugging andForensicsFault monitoringPerformance monitoringTroubleshootingFeature usageSecurity / Incident detectionRegulatoryand standards compliance

12. Functional – non-functionalloggingFunctionalAuditGovernanceSecurityNon-functionalFaults, Errors, ExceptionsExecution contextPerformanceComponent usage

13. Putting italltogetherFunctional LogsCustomerAuditAlways onRequirementsScope knownYears‘Clutter, yuck, slow’Non-Functional LogsSystem operatorDeveloperSometimes onErrors, Exceptions, DebugScope notknownHours, Days‘Mightcome in handy’

14. WHAT to log

15. Keep in mind”Whatwouldhelp YOU at 3 AM in the morning? “Image: Ambro / FreeDigitalPhotos.net

16. Whatwillhelp youExact notice of whathappenedWhenWhereHowWhoClearconcise context informationAnalysis possible without applicationManualSemi-automatedAutomatedRemotelycollectible filesLow footprintProven reliableandauthentic

17. Whatwill help youexamples2011-05-31 08:46:11,308 +0200INFO [eventlog.security] ACCESS OF ProfileServiceImpl.findProfilesBY[login: some_username];Password: [PROTECTED];Authenticated: true;Details: RemoteIpAddress: 192.168.156.17;SessionId: 8XyrNkLWv7FdXS…Granted Authorities:ROLE_USER,ROLE…

18. Whatwon’thelp youNo details about the recordNo context informationInconsistent format or bad useNon-correlatableSubjective/interpretativemessageToo muchuseless log recordsLoggingtoone single big file

19. Whatwon’t help you – example#1log4j: setFile called: ./logs/be/mobistar/network-status/log_functional.log, falselog4j: setFileendedtis nendefaulttis nendefaultActivations : 15Deactivations : 0In straigt to resource filter

20. Whatwon’t help you – example#2INFO [dao.ProductDao] [] - FOUND 40INFO [web.listeners.PhaseLogger] [] - +RENDER_RESPONSEINFO [service.ProductFamilyService] [] - product in family is trueINFO [.dao.ProfileDao] [] - [OBJECTS] find profiles

21. log messagedecomposed

22. “A log record shouldbeunderstandableby a human, andeasily machine processable.”

23. LoggingGuidelines: PrioritiesFatalApplication crash&burnErrorExceptionsMonitoring team alertWarnMonitor health, performanceInfoInformative ContextAudit trailDebugExtensive ContextDevelopment, TestingTroubleshooting

24. LoggingGuidelines: ExceptionsHandlingRecoverLog the details ifcriticalNot Handling, TranslatingTranslateHandling logic ifnotpropagatingNot HandlingPropagateSomeoneelsewill handle (and log!)Chooseexceptionsto logDefendfromstacktrace chaosChoosewhatto log foreachexceptionCatching block has all context details!

25. LoggingGuidelines: Correlation1 transaction = * log recordsCorrelationnecessaryExecutiontrailShared context variableShared per transactionReuse of context variablesNested Diagnostic ContextMap Diagnostic ContextOnlyonecorrelationUse a context uniquevariableCorrelate transactions

26. How to log iN

27. How loggingframeworkswork

28. Java Logging FrameworksImplementationSystem.out – System.errRedirect outputJava UtilLoggingLog4jLogbackAbstractionCommonsLoggingSLF4J

29. Java UtilLoggingJava 1.4+Based on Log4JLess features out of the boxConsoleFileStream

30. Log4jFirst frameworkIntroductionof Logger, Appender, LevelHiearchical LoggersConfigurableappenders, e.g.MailAppenderFileAppenderSMTPAppenderSocketAppenderSyslogAppenderLeader quitandstartedlogback

31. CommonsLoggingApache ProjectAPI BridgeAPI-calls forward toLog4j if on CPFalls back to JULPlaguedDouble ConfigurationRuntime dependency checkClasspathScanningDiscontinuedv1.1.1 dates from end 2007

32. Slf4j - LogbackTwolibrariestorulethemallSlf4jComparablewithcommons-loggingParameter parsingFramework bridgesMuch more powerfulLogbackEvolved log4jImplements Slf4j“Picking up where log4j leaves off”TestingFilters on-need-base

33. SLF4J Binding

34. SLF4J Bridging

35. Keepingit performantString concatenationLOGGER.debug("Hello " + name);Protected blockif (logger.isDebugEnabled()) {LOGGER.debug("Hello " + name);}Slf4jLOGGER.debug("Hello {}", name);

36. Context Variables In PracticeNDC.push(correlationId);app.logMe("Hello world!");NDC.pop();Use %x in PatternConversionPattern= %x %d %m %ncorrelationId 2011-06-21 09:20:41 [INFO] Hello world!

37. Specialized LoggersLogger for classFine-tune logExecutiontraceHow distinguishSecurityPerformance BusinessSpecialized LoggersPrioritiesOutput handlersGroupedlogging

38. Logging In ProductionOnlynecessaryloggingSituation -> turn on debugloggingNo restart: DynamicReloading‘Watch’ file for changesLog file managementRolling fileSeperation of concernsClusteringDifferent systems generatemessagesSynchronization of timestampsCorrelation on host-specific files

39. My OpinionImportance of loggingwillgrowMobile / offline applicationsCloud integrationSystem interactionLogging standards enterprisewideStandardization of logging effortInexpensiveexerciseDraft a standardBuild adapters / patternsEnforce standards

40. Log Processing and analysis

41. Log AnalysisBang foryourbuckXpoLoghttp://www.xpolog.comLicensedFasterSplunkhttp://www.splunk.comFree Edition‘Slow’ AJAX feelNice graphicsModular (http://www.splunkbase.com)Tuningyourpattern is important?

42. Demo

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