Log 4 perl Mike Schilli Yahoo OSCON 07242008
- Slides: 109
Log 4 perl Mike Schilli, Yahoo! OSCON, 07/24/2008
Logging – why? • Debug during development • Go back in time and figure out what happened. • Measure performance • Trace activity on live systems
Why Log 4 perl and not one of the 20 Logging modules on CPAN? • No CPAN dependencies • Easy to use, but scales with complexity • Unique Features
Log: : Log 4 perl Availability • cpan> install Log: : Log 4 perl (Only requires core modules) • Included in major Linux distros sudo apt-get install liblog-log 4 perl • Requires Perl 5. 00503 or better • Windows: ppm package available in Active. State archives or from log 4 perl. com
Use Log 4 perl as a Remote Control to your System.
Log: : Log 4 perl Remote Controls Levels Loggers Layouts Appenders
Log: : Log 4 perl Remote Controls Levels Log/Suppress Priority/Level Loggers Locate it in the system Layouts Format it Appenders Write it out
Log: : Log 4 perl Remote Controls Levels Loggers Layouts Appenders DEBUG “Starting up”; ERROR “Cannot open $file”; Turn logging on in main or Net: : Amazon “Starting up” => 2007 -06 -21 07: 30: 33 Foo. pm-123 Starting up Log File Database …
Sounds complicated? Actually, it’s easy …
Easy Log 4 perl #!/usr/bin/perl –w use strict; use Log: : Log 4 perl qw(: easy); DEBUG “Starting up”;
Don’t like macros? Use get_logger() #!/usr/bin/perl –w use strict; use Log: : Log 4 perl qw(get_logger); my $logger = get_logger(); $logger->debug(“Starting up”);
Like it clean? Use Moose! package Ferrari; use Moose; with “Moose. X: : Log 4 perl”; sub drive { my($self) = @_; $self->log->debug(“Wroom!!”); }
Easy Log 4 perl #!/usr/bin/perl –w use strict; use Log: : Log 4 perl qw(: easy); DEBUG “Starting up”;
Easy Log 4 perl $. /hello $
Easy Log 4 perl #!/usr/bin/perl –w use strict; use Log: : Log 4 perl qw(: easy); Log: : Log 4 perl->easy_init( $DEBUG ); DEBUG “Starting up”;
Easy Log 4 perl $. /hello 2008/07/08 18: 37: 12 Starting up $
Easy Log 4 perl #!/usr/bin/perl –w use strict; use Log: : Log 4 perl qw(: easy); Log: : Log 4 perl->easy_init( $DEBUG ); DEBUG “Starting up”; # … something happens ERROR “Horrible error!”;
Easy Log 4 perl $. /hello 2008/07/08 18: 37: 12 Starting up 2008/07/08 18: 37: 12 Horrible error! $
Easy Log 4 perl #!/usr/bin/perl –w use strict; use Log: : Log 4 perl qw(: easy); Log: : Log 4 perl->easy_init( $ERROR ); DEBUG “Starting up”; ERROR “Horrible error!”;
Easy Log 4 perl $. /hello 2008/07/08 18: 37: 12 Horrible error! $
Remote Control #1: Levels
You get the concept: FATAL ERROR WARNING INFO DEBUG TRACE Message Priority Log Level Configured
Chatty configuration FATAL ERROR WARNING INFO DEBUG TRACE Message Priority TRACE Log Level Configured
Silent configuration FATAL ERROR WARNING INFO DEBUG TRACE Message Priority ERROR Log Level Configured
Log Levels • Choose them wisely – TRACE(“$bytes transferred”); – DEBUG(“HTTP get OK”); – INFO(“Starting up”); – WARN(“HTTP get failed, retrying”); – ERROR(“Out of retries!”); – FATAL(“Panic! Shutting down. ”);
Remote Control #2: Layouts
Location-Awareness • Log 4 perl’s Loggers are aware of their location: package Foo; use Log: : Log 4 perl qw(: easy); sub foo { DEBUG “Starting up”; }
Location-Awareness package Foo; use Log: : Log 4 perl qw(: easy); sub foo { DEBUG “Starting up”; } $. /hello 2008/07/13 19: 32: 39 Starting up
Location-Awareness package Foo; use Log: : Log 4 perl qw(: easy); sub foo { DEBUG “Starting up”; } $. /hello 637 Foo: : foo. /Foo. pm-4> Starting up
Location-Awareness package main; use Log: : Log 4 perl (: easy); Log: : Log 4 perl->easy_init({ level => $DEBUG, layout => “%r %M %F-%L> %m%n”, }); Foo: : foo(); # unchanged! $. /hello 637 Foo: : foo. /Foo. pm-4> Starting up
Configuration Files If this becomes unwieldy: Log: : Log 4 perl->easy_init({ level => $DEBUG, layout => “%r %M %F-%L>%m%n”, });
Configuration Files #l 4 p. conf l 4 p. logger = DEBUG, Screen l 4 p. appender. Screen = Log: : Log 4 perl: : Appender: : Screen l 4 p. appender. Screen. Layout = Pattern. Layout l 4 p. appender. Screen. Layout. Conversion. Pattern = %r %M %F-%L> %m%n Log: : Log 4 perl->init( “l 4 p. conf” );
Advantages of Config Files • Can be edited – indepentently of the script – while the script runs – by people without access to the code
Remote Control #3: Categories (Loggers)
Turn on Logging Everywhere Script l 4 p. logger = DEBUG, Screen Modules
Using Categories Script l 4 p. logger. Net. Amazon = DEBUG, Screen Modules Net: : Amazon
Using Categories main Script l 4 p. logger. main = Modules DEBUG, Screen Net: : Amazon
Using Categories main Script l 4 p. logger. main = DEBUG, Screen l 4 p. logger. Net. Amazon = DEBUG, Screen Modules Net: : Amazon
Categories #l 4 p. conf l 4 p. logger. main = DEBUG, Screen l 4 p. logger. Net. Amazon = DEBUG, Screen l 4 p. appender. Screen = Log: : Log 4 perl: : Appender: : Screen l 4 p. appender. Screen. Layout = Pattern. Layout l 4 p. appender. Screen. Layout. Conversion. Pattern = %r %M %F-%L> %m%n main Net: : Amazon
Category Inheritance #l 4 p. conf l 4 p. logger. Net = DEBUG, Screen l 4 p. appender. Screen = Log: : Log 4 perl: : Appender: : Screen l 4 p. appender. Screen. Layout = Pattern. Layout l 4 p. appender. Screen. Layout. Conversion. Pattern = %r %M %F-%L> %m%n main Net: : Google Net: : Amazon
Remote Control #5: Appenders
Root Logger #l 4 p. conf l 4 p. logger = DEBUG, Screen l 4 p. appender. Screen = Log: : Log 4 perl: : Appender: : Screen l 4 p. appender. Screen. Layout = Pattern. Layout l 4 p. appender. Screen. Layout. Conversion. Pattern = %r %M %F-%L> %m%n main Net: : Google Net: : Amazon
Multiple Appenders #l 4 p. conf l 4 p. logger. main = DEBUG, Screen l 4 p. logger. Net. Amazon = DEBUG, File l 4 p. appender. Screen = Log: : Log 4 perl: : Appender: : Screen l 4 p. appender. Screen. Layout = Simple. Layout l 4 p. appender. File = Log: : Log 4 perl: : Appender: : File l 4 p. appender. File. filename = /var/log/myapp. log l 4 p. appender. File. Layout = Pattern. Layout l 4 p. appender. File. Layout. Conversion. Pattern = %r %M %F-%L> %m%n main Screen Net: : Amazon File
Multiple Appenders (different log levels) #l 4 p. conf l 4 p. logger. main = DEBUG, Screen l 4 p. logger. Net. Amazon = ERROR, File l 4 p. appender. Screen = Log: : Log 4 perl: : Appender: : Screen l 4 p. appender. Screen. Layout = Simple. Layout l 4 p. appender. File = Log: : Log 4 perl: : Appender: : File l 4 p. appender. File. filename = /var/log/myapp. log l 4 p. appender. File. Layout = Pattern. Layout l 4 p. appender. File. Layout. Conversion. Pattern = %r %M %F-%L> %m%n main Screen Net: : Amazon File
Multiple Appenders #l 4 p. conf l 4 p. logger. main = DEBUG, Screen, File l 4 p. appender. Screen = Log: : Log 4 perl: : Appender: : Screen l 4 p. appender. Screen. Layout = Simple. Layout l 4 p. appender. File = Log: : Log 4 perl: : Appender: : File l 4 p. appender. File. filename = /var/log/myapp. log l 4 p. appender. File. Layout = Pattern. Layout l 4 p. appender. File. Layout. Conversion. Pattern = %r %M %F-%L> %m%n main Screen Net: : Amazon File
Log 4 perl Flow Application sends a log message (Category, Priority) Log 4 perl Configuration decides go/no go, based on Category and Priority ? Layout Appender
Log 4 perl and Log 4 j • Log: : Log 4 perl ports Log 4 j to Perl • Log 4 j: de facto Java logging standard, by Ceki Gülcü – Latest development: ‘logback’ • http: //logging. apache. org/log 4 j • Log: : Log 4 perl adds perlisms demanded by users
Log 4 perl History • • 0. 01 release 2002 Current release 1. 17 (07/2008) Authors: Mike Schilli, Kevin Goess Used by major banks, target. com, fedex. com, Yahoo!, Google, … • Several CPAN modules support it (e. g. Catalyst, Net: : Amazon, …) • Every major Linux distro has it (Ubuntu, Suse, Fedora …)
Log 4 perl Release History
Design Goals • Easy to use in small scripts • Scales easily with growing architecture • Log 4 perl-enabled CPAN modules can be used with and without Log 4 perl initialization • Optimized for Speed • Open Architecture, extensible
Combine Remote Controls • Write code once, and L 4 p-enabled scripts/modules can be used – with any logging configuration you desire – by changing loggers, appenders and layouts independently – similar to dtrace probes • No need to change your source code to change the logging behavior
Init and Watch • Log: : Log 4 perl->init(“l 4 p. conf”); • Log: : Log 4 perl->init($conf_string); • Log: : Log 4 perl->init_and_watch(“l 4 p. conf”, 30); • Log: : Log 4 perl->init_and_watch(“l 4 p. conf”, ‘HUP’ );
Demo
Appenders • Appenders are output sinks • Get called if a message passes category and level hurdles
Appenders • Log: : Log 4 perl: : Appender: : Screen Log: : Log 4 perl: : Appender: : File Log: : Log 4 perl: : Appender: : Socket Log: : Log 4 perl: : Appender: : DBI Log: : Log 4 perl: : Appender: : Synchronized Log: : Log 4 perl: : Appender: : RRDs • Log: : Dispatch provides even more:
Log: : Dispatch Appenders • Log: : Dispatch: : Apache. Log: : Dispatch: : DBI, Log: : Dispatch: : Email: : MIMELite Log: : Dispatch: : File. Rotate Log: : Dispatch: : Screen Log: : Dispatch: : Syslog, Log: : Dispatch: : Tk
Example: Rotating Log File Appender • Keep 5 days of logfiles, then delete: log 4 perl. category = WARN, Logfile log 4 perl. appender. Logfile = Log: : Dispatch: : File. Rotate log 4 perl. appender. Logfilename = test. log 4 perl. appender. Logfile. max = 5 log 4 perl. appender. Logfile. Date. Pattern = yyyy-MM-dd log 4 perl. appender. Logfile. TZ = PST log 4 perl. appender. Logfile. layout = Log: : Log 4 perl: : Layout: : Simple. Layout
Rotating Files • Rotating File Appender: – Log: : Dispatch: : File. Rotate – Single request pays for rotation – Rotation runs as particular user • External Rotators (e. g. newsyslog): – recreate flag makes sure file appender adjusts – recreate_check_interval saves on stat() calls
Layouts • Simple. Layout log 4 perl. appender. Screen = Log: : Log 4 perl: : Appender: : Screen log 4 perl. appender. Screen. layout = Simple. Layout $log->debug(“Sending Mail”); DEBUG – Sending Mail
Layouts • Pattern. Layout log 4 perl. appender. Logfile. layout = Log: : Log 4 perl: : Layout: : Pattern. Layout log 4 perl. appender. Logfile. layout. Conversion. Pattern = %d %F{1}: %L> %m %n $log->debug(“Sending Mail”); 2004/10/17 18: 47: 25 l 4 ptest. pl: 25> Sending Mail
Layouts • Pattern. Layout %T stack trace %c Category of the logging event. %C Fully qualified package (or class) name of the caller %d Current date in yyyy/MM/dd hh: mm: ss format %F File where the logging event occurred %H Hostname %l calling method + file + line %L Line number within the file where the log statement was issued %m The message to be logged %M Method or function where the logging request was issued %n Newline (OS-independent) %p Priority of the logging event %P pid of the current process %r Number of milliseconds elapsed from program start %x The elements of the NDC stack %X{key} The entry 'key' of the MDC %% A literal percent (%) sign
Layouts • Still not enough? Write your own: log 4 perl. Pattern. Layout. cspec. U = sub { return "UID $<" } … log 4 perl. appender. Logfile. layout = Log: : Log 4 perl: : Layout: : Pattern. Layout log 4 perl. appender. Logfile. layout. Conversion. Pattern = %d %U> %m %n
Speed
Benchmarks • 1 M/sec suppressed calls • 50 k/sec logged messages (memory appender) • No degradation with subcategories
Avoid Wasting Cycles for (@super_long_array) { $logger->debug("Element: $_n"); } if($logger->is_debug()) { for (@super_long_array) { $logger->debug("Element: $_n"); } }
Dirty Tricks
Resurrect in a Single File • The : resurrect target uncomments lines starting with ###l 4 p: use Log 4 perl qw(: easy : resurrect); sub foo { # … ###l 4 p DEBUG “foo was here”; }
Resurrect L 4 p in all Modules • The Log: : Log 4 perl: : Resurrector touches all subsequently loaded modules (experimental!): use Log 4 perl qw(: easy); use Log: : Log 4 perl: : Resurrector; use Foo: : Bar; # Deploy a module without requiring L 4 p at all! package Foo: : Bar; ###l 4 p use Log 4 perl qw(: easy); sub foo { ###l 4 p DEBUG “This will be resurrected!”; }
The Future
Wouldn’t it be nice … • … if all modules on CPAN had a standard logging interface?
Log 4 perl-enable a CPAN Module package Foo; sub foo { # … do something } 1;
Log 4 perl-enable a CPAN Module package Foo; use Log: : Log 4 perl qw(: easy); sub foo { # … do something DEBUG “Fooing $bar”; } 1;
… and voila, your CPAN module has a built-in remote.
Be Open • Let other people debug your module in a standard way.
Q&A
Thank You! Log: : Log 4 perl Project Page (includes slides of this talk): http: /log 4 perl. com Email me: Mike Schilli mschilli@yahoo-inc. com
Don’t forget to submit a Review! • Go to the OSCON schedule, click on this talk and then ‘rate this talk’ • Thanks!
Bonus Slides
Advanced Trickery
Infiltrating LWP • Ever wondered what LWP is doing behind the scenes? use LWP: : User. Agent; use HTTP: : Request: : Common; use Log: : Log 4 perl qw(: easy); Log: : Log 4 perl->easy_init($DEBUG); Log: : Log 4 perl->infiltrate_lwp(); my $ua = LWP: : User. Agent->new(); my $resp = $ua->request(GET "http: //www. yahoo. com");
Infiltrating LWP • Getting LWP to use Log 4 perl for logging: 2004/10/20 18: 36: 43 () 2004/10/20 18: 36: 43 GET http: //www. yahoo. com 2004/10/20 18: 36: 43 Not proxied 2004/10/20 18: 36: 43 () 2004/10/20 18: 36: 43 read 634 bytes 2004/10/20 18: 36: 43 read 4096 bytes … 2004/10/20 18: 36: 43 read 2488 bytes 2004/10/20 18: 36: 43 Simple response: OK
Pitfalls Beginner’s Pitfalls
Beginner’s Pitfalls • Appender Additivity: – Once a lower level logger decides to fire, it will forward the message to its appenders. – It will also forward the message unconditionally to all of its parent logger’s appenders.
Beginner’s Pitfalls • Appender Additivity (with dupes) log 4 perl. category = FATAL, Screen log 4 perl. category. Net. Amazon = DEBUG, Screen log 4 perl. appender. Screen = Log: : Log 4 perl: : Appender: : Screen log 4 perl. appender. Screen. layout = Simple. Layout package Net: : Amazon; DEBUG(“Debugging!”); DEBUG - Debugging!
Appender Additivity File Appender root FATAL Screen Appender Net: : Amazon DEBUG
Beginner’s Pitfalls • Appender Additivity (no dupes) log 4 perl. category = ERROR, Screen log 4 perl. category. Net. Amazon = DEBUG, Screen log 4 perl. additivity. Net. Amazon = 0 log 4 perl. appender. Screen = Log: : Log 4 perl: : Appender: : Screen log 4 perl. appender. Screen. layout = Simple. Layout package Net: : Amazon; DEBUG(“Debugging!”); DEBUG – Debugging! Q
Write Your Own Appender (1) package Color. Screen. Appender; our @ISA = qw(Log: : Log 4 perl: : Appender); use Term: : ANSIColor; sub new { my($class, %options) = @_; my $self = {%options, …}; bless $self, $class; } sub log { my($self, %params) = @_; print colored($params{message}, $self->{color}); }
Write Your Own Appender (2) log 4 perl. logger = INFO, Color. App log 4 perl. appender. Color. App=Color. Screen. Appender log 4 perl. appender. Color. App. color = red log 4 perl. appender. Color. App. layout = Simple. Layout
Filters • Last minute chance for Appenders to block • More expensive than Level/Category blocking • Text/Level Match comes with L 4 p • Write your own custom filters
Filters log 4 perl. category = INFO, Screen log 4 perl. filter. My. Filter = Log: : Log 4 perl: : Filter: : String. Match log 4 perl. filter. M 1. String. To. Match = let this through log 4 perl. appender. Screen = Log: : Log 4 perl: : Appender: : Screen log 4 perl. appender. Screen. Filter = My. Filter log 4 perl. appender. Screen. layout = Log: : Log 4 perl: : Layout: : Simple. Layout
Filters log 4 perl. filter. M 1 = Log: : Log 4 perl: : Filter: : String. Match log 4 perl. filter. M 1. String. To. Match = let this through log 4 perl. filter. M 1. Accept. On. Match = true log 4 perl. filter. M 1 = Log: : Log 4 perl: : Filter: : Level. Match log 4 perl. filter. M 1. Level. To. Match = INFO log 4 perl. filter. M 1. Accept. On. Match = true
Best Practices • Don’t provide program name, function name in the message. Use Layouts instead. • Log plenty. Don’t worry about space, use rotating log files for chatty output.
What you should log • • Program starting up, shutting down Function parameters Milestones in request processing Start/end of lenghty operations (e. g. DB access) • result of called function (logged in calling function)
What you shouldn’t log • Function/method names (although you want parameters) • Date • Process ID • … everything else provided by the layout
Error Handling use Log: : Log 4 perl qw(: easy); do_something or LOGDIE “Horrible error!”; • LOGCARP, LOGCLUCK, LOGCONFESS etc. also available.
Best Practices • Rolling out new L 4 p-enabled Modules package My: : Module; use Log: : Log 4 perl qw(: easy); sub new { # … } sub foo { DEBUG “I’m here”; # … } sub bar { INFO “Now I’m here”; # … } # Use w/o Log 4 perl use My: : Module; $o = My: : Module->new(); $o->foo(); # Log 4 perl enabled use My: : Module; use Log: : Log 4 perl qw(: easy); Log: : Log 4 perl->easy_init($DEBUG); $o = My: : Module->new(); $o->foo();
Gotchas • Avoid ‘append’ on NFS (creating lots of ‘read’ traffic) • Don’t put expensive operations into the logger call which are executed before the logger decides • Permission issues with rotating file appenders
mod_perl • Init() in startup handler • Current limitation: One init(). • Use init_once() if you’re not sure who inits first.
Combat overlapping Messages • Either live with it or – Use the Synchronized appender – Use Appender. File. syswrite=1
Driving Log: : Log 4 perl further • Bug Fixes: Submit to log 4 perl-devel@sourceforge. net • New Features: Propose features or send patches • New Appenders: Release separately as a module in the Log: : Log 4 perl: : Appender: : xx namespace on CPAN • … or contact me: mschilli@yahoo-inc. com
Easy Mode Init with Files use Log: : Log 4 perl qw(: easy); Log: : Log 4 perl->easy_init({ level => $DEBUG, file => “>file. log”, category => “Bar: : Twix”, });
Multiline Layout Instead of 2007/04/04 23: 59: 01 This is a message with multiple lines get this: 2007/04/04 23: 59: 01 This is 2007/04/04 23: 59: 01 a message with 2007/04/04 23: 59: 01 multiple lines with Pattern. Layout: : Multiline: log 4 perl. appender. Logfile. layout = Log: : Log 4 perl: : Layout: : Pattern. Layout: : Multiline log 4 perl. appender. Logfile. layout. Conversion. Pattern = %d %m %n
Perl Hooks • Add parameters known at init() time log 4 perl. appender. Logfilename = sub { “mylog. $$. log” }
Loggers • Have a – category (e. g. “Net: : Amazon” ) – priority (e. g. $DEBUG ) • Take a message (e. g. “Starting” )
Loggers • Pass on their message if – logging has been configured for • their category ( “Net: : Amazon”) or • a parent category ( “Net”, “” ) – and (!) the message priority (e. g. $DEBUG) is greater or equal than the configured log level (e. g. $DEBUG) for the category
Limit Throughput: Levels and Categories • Categories determine which parts of the system are addressed. my $log = get_logger(“Net: : Amazon”); or simply package Net: : Amazon; DEBUG “…”; • Levels indicate the message priority. $log->debug(“Request sent ($bytes)”;
Displaying Logs with Chainsaw • Log 4 j features an XML layout and a socket appender • XML output is displayed in a nice GUI called Chainsaw • Log: : Log 4 perl also features an XML layout and a socket appender • … XML output is also displayed in a nice GUI called Chainsaw!
Displaying Logs with Chainsaw Log: : Log 4 perl enabled Perl Script Log: : Log 4 perl: : Layout: : XML Log: : Log 4 perl: : Appender: : Socket Java / log 4 j Program
Displaying Logs with Chainsaw
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