use 5.014; #package Thread::Queue::Monitored '1.03'; # not supported by PAUSE/MetaCPAN :-( package Thread::Queue::Monitored; # please remove if no longer needed # initializations our @ISA= qw( Thread::Queue ); our $VERSION= '1.03'; # please remove if no longer needed # be as verbose as possible use warnings; # modules that we need use Thread::Queue (); # no need to pollute namespace # self referencing within monitoring thread my $SELF; # satisfy -require- 1; #------------------------------------------------------------------------------- # new # # Create a monitored queue # # IN: 1 class to bless with # 2 reference/name of subroutine doing the monitoring # 3 value to consider end of monitoring action (default: undef) # OUT: 1 instantiated object # 2 (optional) thread object of monitoring thread sub new { my $class= shift; my $param= shift; # sanity check my $monitor= $param->{monitor}; die "Must specify a subroutine to monitor the queue" if !$monitor; # make sure it is a code ref my $namespace= caller() . '::'; $monitor= _makecoderef( $namespace, $monitor ) if !ref($monitor); # get pre and post code my $pre= $param->{pre}; $pre= _makecoderef( $namespace, $pre ) if $pre and !ref($pre); my $post= $param->{post}; $post= _makecoderef( $namespace, $post ) if $post and !ref($post); # obtain the queue object my $self= $param->{queue} ? bless $param->{queue}, $class : $class->SUPER::new; # create the thread no strict 'refs'; my $thread= threads->new( \&{ $class . '::_monitor' }, $self, wantarray, $monitor, $param->{exit}, # don't care if not available: then undef = exit value $post, $pre, @_, ); return wantarray ? ($self,$thread) : $self; } #new #------------------------------------------------------------------------------- # self # # return singleton # # IN: 1 class (ignored) # OUT: 1 instantiated queue object sub self { $SELF } #self #------------------------------------------------------------------------------- # dequeue # # not allowed to do this # # IN: 1 instantiated object (ignored) # OUT: 1 dequeued value (not returned) sub dequeue { _die() } #dequeue #------------------------------------------------------------------------------- # dequeue_dontwait # # not allowed to do this # # IN: 1 instantiated object (ignored) # OUT: 1 dequeued value (not returned) sub dequeue_dontwait { _die() } #dequeue_dontwait #------------------------------------------------------------------------------- # dequeue_nb # # not allowed to do this # # IN: 1 instantiated object (ignored) # OUT: 1 dequeued value (not returned) sub dequeue_nb { _die() } #dequeue_nb #------------------------------------------------------------------------------- # dequeue_keep # # not allowed to do this # # IN: 1 instantiated object (ignored) # OUT: 1 dequeued value (not returned) sub dequeue_keep { _die() } # dequeue_keep #------------------------------------------------------------------------------- # # Internal subroutines # #------------------------------------------------------------------------------- # _die # # die as if in caller # # IN: 1 instantiated object (ignored) sub _die { ( my $caller= ( caller(1) )[3] ) =~ s#^.*::##; die "You cannot '$caller' on a monitored queue"; } #_die #------------------------------------------------------------------------------- # _makecoderef # # Return coderef for given namespace / sub # # IN: 1 namespace prefix # 2 subroutine name # OUT: 1 code reference sub _makecoderef { my ( $namespace, $code )= @_; # ensure fully qualified $code= $namespace.$code if $code !~ m#::#; return \&{$code}; } #_makecoderef #------------------------------------------------------------------------------- # _monitor # # monitor a queue # # IN: 1 queue object to monitor # 2 flag: to keep thread attached # 3 code reference of monitoring routine # 4 exit value # 5 code reference of preparing routine (if available) # 6..N parameters passed to creation routine sub _monitor { my $queue= $SELF= shift; threads->self->detach if !shift; my $monitor= shift; my $exit= shift; # get pre/post processing my $post= shift || sub {}; my $pre= shift; $pre->( @_ ) if $pre; # processing my @value; while (1) { # get all values from the queue { lock( @{$queue} ); threads::shared::cond_wait @{$queue} until @{$queue}; @value= @{$queue}; @{$queue}= (); } # process all values foreach (@value) { # done, we've seen the exit value return $post->(@_) when $exit; # perform the monitoring for this value $monitor->($_); } } } #_monitor #------------------------------------------------------------------------------- __END__ =head1 NAME Thread::Queue::Monitored - monitor a queue for specific content =head1 SYNOPSIS use Thread::Queue::Monitored; my ( $q, $t)= Thread::Queue::Monitored->new( { monitor => sub { print "monitoring value $_[0]\n" }, # is a must pre => sub { print "prepare monitoring\n" }, # optional post => sub { print "stop monitoring\n" }, # optional queue => $queue, # use existing queue, create new if not specified exit => 'exit', # default to undef } ); $q->enqueue("foo"); $q->enqueue(undef); # exit value by default @post= $t->join; # optional, wait for monitor thread to end $queue= Thread::Queue::Monitored->self; # "pre", "do", "post" only =head1 VERSION This documentation describes version 1.03. =head1 DESCRIPTION *** A note of CAUTION *** This module only functions if threading has been enabled when building Perl, or if the "forks" module has been installed on an unthreaded Perl. ************************* A queue, as implemented by C is a thread-safe data structure that inherits from C. But unlike the standard C, it starts a single thread that monitors the contents of the queue by taking new values off the queue as they become available. It can be used for simply logging actions that are placed on the queue. Or only output warnings if a certain value is encountered. Or whatever. The action performed in the thread, is determined by a name or reference to a subroutine. This subroutine is called for every value obtained from the queue. Any number of threads can safely add elements to the end of the list. =head1 CLASS METHODS =head2 new ( $queue, $thread )= Thread::Queue::Monitored->new( { pre => \&pre, monitor => 'monitor', post => 'module::done', queue => $queue, # use existing queue, create new if not specified exit => 'exit', # default to undef } ); The C function creates a monitoring function on an existing or on an new (empty) queue. It returns the instantiated Thread::Queue::Monitored object in scalar context: in that case, the monitoring thread will be detached and will continue until the exit value is passed on to the queue. In list context, the thread object is also returned, which can be used to wait for the thread to be really finished using the C method. The first input parameter is a reference to a hash that should at least contain the "monitor" key with a subroutine reference. The other input parameters are optional. If specified, they are passed to the the "pre" routine which is executed once when the monitoring is started. The following field B be specified in the hash reference: =over 2 =item do monitor => 'monitor_the_queue', # assume caller's namespace or: monitor => 'Package::monitor_the_queue', or: monitor => \&SomeOther::monitor_the_queue, or: monitor => sub { print "anonymous sub monitoring the queue\n" }, The "monitor" field specifies the subroutine to be executed for each value that is removed from the queue. It must be specified as either the name of a subroutine or as a reference to a (anonymous) subroutine. The specified subroutine should expect the following parameter to be passed: 1 value obtain from the queue What the subroutine does with the value, is entirely up to the developer. =back The following fields are B in the hash reference: =over 2 =item pre pre => 'prepare_monitoring', # assume caller's namespace or: pre => 'Package::prepare_monitoring', or: pre => \&SomeOther::prepare_monitoring, or: pre => sub {print "anonymous sub preparing the monitoring\n"}, The "pre" field specifies the subroutine to be executed once when the monitoring of the queue is started. It must be specified as either the name of a subroutine or as a reference to a (anonymous) subroutine. The specified subroutine should expect the following parameters to be passed: 1..N any parameters that were passed with the call to L. =item post post => 'stop_monitoring', # assume caller's namespace or: post => 'Package::stop_monitoring', or: post => \&SomeOther::stop_monitoring, or: post => sub {print "anonymous sub when stopping the monitoring\n"}, The "post" field specifies the subroutine to be executed once when the monitoring of the queue is stopped. It must be specified as either the name of a subroutine or as a reference to a (anonymous) subroutine. The specified subroutine should expect the following parameters to be passed: 1..N any parameters that were passed with the call to L. Any values returned by the "post" routine, can be obtained with the C method on the thread object. =item queue queue => $queue, # create new one if not specified The "queue" field specifies the Thread::Queue object that should be monitored. A new L object will be created if it is not specified. =item exit exit => 'exit', # default to undef The "exit" field specifies the value that will cause the monitoring thread to seize monitoring. The "undef" value will be assumed if it is not specified. This value should be Ld to have the monitoring thread stop. =back =head2 self $queue = Thread::Queue::Monitored->self; # only "pre", "do" and "post" The class method "self" returns the object for which this thread is monitoring. It is available within the "pre", "do" and "post" subroutine only. =head1 OBJECT METHODS =head2 enqueue $queue->enqueue( $value1, $value2 ); $queue->enqueue( 'exit' ); # stop monitoring The C method adds all specified parameters on to the end of the queue. The queue will grow as needed to accommodate the list. If the "exit" value is passed, then the monitoring thread will shut itself down. =head1 REQUIRED MODULES Test::More (0.88) Thread::Queue (any) =head1 INSTALLATION This distribution contains two versions of the code: one maintenance version for versions of perl < 5.014 (known as 'maint'), and the version currently in development (known as 'blead'). The standard build for your perl version is: perl Makefile.PL make make test make install This will try to test and install the "blead" version of the code. If the Perl version does not support the "blead" version, then the running of the Makefile.PL will *fail*. In such a case, one can force the installing of the "maint" version of the code by doing: perl Makefile.PL maint Alternately, if you want automatic selection behavior, you can set the AUTO_SELECT_MAINT_OR_BLEAD environment variable to a true value. On Unix-like systems like so: AUTO_SELECT_MAINT_OR_BLEAD=1 perl Makefile.PL If your perl does not support the "blead" version of the code, then it will automatically install the "maint" version of the code. =head1 CAVEATS You cannot remove any values from the queue, as that is done by the monitoring thread. Therefore, the methods "dequeue", "dequeue_dontwait", "dequeue_nb" and "dequeue_keep" are disabled on this object. =head1 AUTHOR Elizabeth Mattijsen, . Please report bugs to . =head1 COPYRIGHT Copyright (c) 2002, 2003, 2007, 2012 Elizabeth Mattijsen . All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =head1 SEE ALSO L, L, L. =cut