Log4s A Logging Framework for Smalltalk

Transcription

1 Log4s A Logging Framework for Smalltalk Donald MacQueen [ ] Instantiations, Inc.

2 Infrastructure Logging Framework Problem: The product currently contains many one-off logging solutions, but no centralized facility useable by product developers and customers. Solution: Provide a Logging Framework to standardize the definition, use, and output formats of logging.

3 log4j Log4j is a popular Java logging framework Easy to configure Extensible Fast Non-intrusive Supports multiple outputs Mature Uses a printf-like syntax to format output Has many Unit Tests!

4 Infrastructure Logging Framework Log4s is based on ideas from the popular Java logging framework log4j

5 The Players LogManager: the Director LoggingEvent: the entity which is logged Logger: the object that does the logging Appender: the output destination Level: controls what gets logged Filter: further controls what gets logged

6 Example LoggingEvent Hi, Mom Logger Appender Hi, Mom EsLogManager info: Hi, Mom

7 LoggingEvent instvars message: a string or a block that evaluates to a string. Example: EsLogManager info: [ Hi %1 bindwith: auserid ] timestamp: the creation time level: the level or priority of the loggingevent Optional depending on the Api used classname: the class name of the object that created the loggingevent methodname: the method name of the object that created the loggingevent threadname: the name of the current thread object: any object you want

8 Loggers Case sensitive name Have one or more appenders Can be created programmatically The logger named root always exists

9 Logger Example LoggingEvent Hi, Mom Logger named Vast Console Appender Hi, Mom File Appender Hi, Mom EsLogManager loggernamed: Vast info: Hi, Mom

10 Appenders Case sensitive name Belong to a logger Have a Level Have 0 n Filters Decide if a loggingevent gets logged

11 Transcript Console Socket File Appenders II Single file Rolling by size - x versions of size y each Rolling by time Twice a day Every minute Every hour Every day Every week Every month

12 Instance variables: Levels level: integer levelstr: name syslogequivalent: integer LoggingEvents and Appenders have levels Appenders log only loggingevents with a level >= to their own level Log4s has 7 predefined levels

13 Levels II ALL SmallInteger smallest ini file only DEBUG INFO WARN ERROR FATAL OFF SmallInteger largest ini file only

14 Level Example LoggingEvent WARN Hi, Mom Logger Appender INFO Bit bucket No loggingevent level >= Appender level? Yes Hi, Mom EsLogManager warn: Hi, Mom

15 Filters Check the contents of a loggingevent Check is done after the appender level check 0 to n can be attached to an appender Filters are and ed; all must pass

16 Class name Pre-defined Filters Level match Range of levels match String Can be set case in/sensitive Hi, Mom or HI, MOM or hi, mom All filters can be set to not match

17 Filter Example LoggingEvent WARN Hi, Mom Logger Appender INFO loggingevent level >= Appender level? Hi, Mom Yes String match on Fred Hi, Mom contains No Bit bucket Fred?

18 LogManager Singleton of the class EsLogManager Creates and manages Loggers, Appenders, LoggingEvents, and Filters Reads the [log4s] stanza in the ini file Holds a global level from a ini file setting (aloggingevent level >= EsLogManager level and: [aloggingevent level >= appender level])

19 LogManager APIs EsLogManager info: All is well EsLogManager loggernamed: Vast warn: Disk is 90% full EsLogManager error: Zero divide locationinfo: self currentclassandmethod EsLogManager debug: Oh, no! object: self. EsLogManager fatal: We are toast locationinfo: self currentclassandmethod object: self owner.

20 Specifying the Log Entry Each Appender must have a layout Each layout has a pattern which is a printf-like string that describes what should be output The pattern string consists of conversion specifiers and literals in any order. For example, '%m' logs only the loggingevent message. Conversion specifiers are mapped to PatternConverter objects The mapping table is in EsPatternParser class>> initializepatternlayoutrules

21 The '%o' or '%object' specifier Used to do custom formatting of the object instance variable in the LoggingEvent Log4s will send the object the #printlog4s message if it responds to it Otherwise, log4s will send the object the #printstring message

22 Infrastructure Logging Framework Example of application logging requirement A banking company is required to keep monthly logs of all foreign transactions and weekly logs of all foreign transactions greater than $10000

23 Infrastructure Logging Framework Example of application logging solution Make.ini file entries [log4s] createlogger=('vast') dailyrollingfileappender=(foreigntxns, root, c:\logs\foreigntxns.log, false, info, EsPatternLayout, '%d [%c] %o', true, topofmonth) dailyrollingfileappender=(bigforeigntxns, vast, c:\logs\bigforeigntxns.log, false, warn, EsPatternLayout, '%d %c %o', true, topofweek) The pattern of %d %c %o will log the time, the logger name, and the transaction object.

24 Infrastructure Logging Framework Define Transaction>>printLog4s ^ String streamcontent: [ :stream stream nextputall: self payee; space; nextputall: self amount printstring ] The application code might look like this: logifneeded: atransaction atransaction isforeign iftrue: [ EsLogManager info: 'Foreign txn object: atransaction. "goes to root logger" atransaction amount > iftrue: [ EsLogManager loggernamed: 'vast warn: 'Large Foreign txn object: atransaction ] ].

25 Result Infrastructure Logging Framework foreigntxns.log will have output like this: '28 Aug :15:07,000 [root] Mark Twain bigforeigntxns.log will have output like this: '28 Aug :15:07,000 vast Fred Smith '

26 Other Formatting %d outputs the date as dd MMM yyyy HH:mm:ss,SSS 28 Aug :15:07,000 Options to %d are enclosed in {} %d{yyyy-mm-dd} %d{hh:mm:ss} 20:15:07 %d{yyyy_mmm_dd EE} 1989_Aug_28 Mon Log4s has justification and width options left justification is the minus (-) character, e.g. '%-m'. minimum width is a decimal constant, e.g., '%15m' maximum field is a period followed by a decimal constant, e.g. '%.20m'

27 globallevel=all Ini File Log4s Stanza (aloggingevent level >= EsLogManager level and: [aloggingevent level >= appender level]) globallevel=off will disable all logging debugenabled=true False will report only errors to TranscriptTTY quietmode=false Log4s will be completely silent if set to false

28 AsyncAppender An asyncappender is attached to a logger Other real appenders are attached to it LoggingEvents sent to an asyncappender are put on a messagequeue Control returns immediately to the caller A background task processes the messagequeue

29 AsyncAppender II LoggingEvent WARN Hi, Mom Logger asyncappender (no level) aynscrollingfileappender Level=WARN (WARN = WARN) consoleappender Level=ERROR (WARN < ERROR) aynscfileappender Level=INFO (WARN > INFO) Yes No Yes Hi, Mom Bit bucket Hi, Mom

30 Exciting Demo Next!