I posted an earlier version of this script to my blog and it worked fine but there was one little problem with it. When we processed the files, namely running eye3D, we did so synchronously. Essentially, the file notification came in from the Linux kernel and we processed the file at that time. This may be an issue of overflowing the inotify queue within the Linux kernel if there are a lot of files to process.
A better solution would be to add the file to an internal queue and process the files in a sub process using POE::Wheel::Run. Of course we will limit the number of sub processes :)
In order to use this, we would start the script and then copy the mp3s into the watched directory in whatever fashion we wished.
#!/usr/bin/perl
use strict;
use warnings;
use File::Basename;
use File::Find ();
use Getopt::Std;
use Linux::Inotify2;
use POE qw( Kernel Session Wheel::Run );
$|++;
#######################################
#######################################
our @found_dirs;
our $max_concurrent_tasks;
sub watch_add_dir {
my ($heap_ref, $session, $dir_name) = @_;
##############
# Watch this directory with a call back
# to the watch_hdlr() subroutine via
# a message to the POE system
##############
$heap_ref->{inotify}->watch($dir_name, IN_CREATE|IN_CLOSE_WRITE, $ses
+sion->postback("watch_hdlr"));
print " Watching directory $dir_name\n";
}
sub watch_hdlr {
my ($kernel, $heap, $session, $event) = ( $_[KERNEL], $_[HEAP], $_[SE
+SSION], $_[ARG1][0] );
my $name = $event->fullname;
my $short_name = $event->name;
##############
# We can receive many many notifications
# for a file. If we’ve already processed
# the file, do nothing.
##############
unless ($heap->{inotify}{files}{$name}) {
##############
# If a new directory is added, we need
# to watch that directory too.
##############
if ($event->IN_CREATE && -d $name) {
print "New directory: $name\n";
watch_add_dir($heap, $session, $name);
} elsif ($event->IN_CLOSE_WRITE) {
##############
# When a file descriptor that was opened for
# ’writing’ is closed, then process that
# file it was being written to. We’re
# assuming that the file is complete at this
# point as the operation will be a copy into
# the watched directory
##############
my $ext = ( fileparse($name, ‘\..*’) )[2];
if (lc($ext) eq ‘.mp3′) {
##############
# Add the file to the file process queue
##############
push @{ $heap->{task}{task_files} }, $name;
##############
# Mark that we have processed the file. If
# we don’t we will end up processing the file
# in an infinite loop because we are modifying
# the files.
##############
$heap->{inotify}{files}{$name} = 1;
##############
# Yield to "task_next_file" through so
# that we can process files in the queue.
##############
$kernel->yield("task_next_file");
}
$heap->{inotify}{files}{$name} = 1;
}
}
##############
# While possible, it is highly unlikely that we will
# overflow the notification buffers within the Linux
# kernel. If so, we should report that.
##############
print "events for $name have been lost\n" if $event->IN_Q_OVERFLOW;
}
sub task_next_file {
my ($kernel, $heap) = @_[ KERNEL, HEAP ];
##############
# Process the files in the queue up
# to the $max_concurrent_tasks at
# once. Any extras will be processed
# when a file (task) completes.
##############
while ( keys( %{ $heap->{task} } ) < $max_concurrent_tasks ) {
my $next_task_file = shift @{ $heap->{task}{task_files} };
##############
# If the $next_task_file is empty, then we can safely
# ignore it.
##############
last unless defined $next_task_file;
##############
# Use POE::Wheel::Run to fire off the
# file processing using a sub process
# to the process_file() subroutine
##############
my $task = POE::Wheel::Run->new (
Program => sub { process_file($next_task_file) },
StdoutEvent => "task_output",
CloseEvent => "task_done",
);
##############
# Update the session with the task
# information and the kernel with
# the SIG_CHILD handler. These are
# necessary for the task to execute.
##############
$heap->{task}->{ $task->ID } = $task;
$kernel->sig_child( $task->PID, "sig_child");
}
}
sub process_file {
my $file = shift;
print " Processed \"$file\"\n";
##############
# Use the eyeD3 package to convert
# the mp3 id3v2/3/4 to id3v1. If
# eyeD3 fails, we don’t really care. :)
##############
my $cmd_output = `eyeD3 –to-v1.1 "$file"`;
$cmd_output = `eyeD3 –remove-v2 "$file"`;
}
sub find_wanted {
my $object = $File::Find::name;
if (-d $object) {
push @found_dirs, $object;
}
}
#######################################
#######################################
#######################################
my %arg_options;
my $watch_dir;
getopts(‘d:t:’, \%arg_options);
if ($arg_options{d} && -d $arg_options{d}) {
$watch_dir = $arg_options{d};
if ($arg_options{t} && $arg_options{t} =~ /^\d+/) {
$max_concurrent_tasks = $arg_options{t};
} else {
$max_concurrent_tasks = 2;
}
##############
# We need to watch all existing sub directories
# so we will find them and add them to the
# @found_dirs array to be added to the watched
# directories when we create the Inotify object
##############
File::Find::find({wanted => \&find_wanted}, $watch_dir);
POE::Session->create
( inline_states =>
{ _start => sub {
my $inotify_FH;
##############
# alias this particular POE session to
# ’notify’ so we can easily reference
# it later if needed
##############
$_[KERNEL]->alias_set(‘notify’);
##############
# Create the Linux::INotify object
##############
$_[HEAP]{inotify} = new Linux::Inotify2
or die "Unable to create new inotify object: $!";
##############
# Add the preexisting directories to
# be watched from the @found_dirs array
##############
foreach my $dir (@found_dirs) {
watch_add_dir($_[HEAP], $_[SESSION], $dir);
}
##############
# We need to create a hash in the "notify"
# POE session so we can determine if we’ve
# processed a file already
##############
$_[HEAP]{inotify}{files} = {};
##############
# The Inotify notifications are received
# on a file descriptor. We need to read
# from it when there is something to be
# read
##############
open $inotify_FH, "< &=" . $_[HEAP]{inotify}->fileno
or die "Can’t fdopen: $!\n";
##############
# Inform POE to poll the file descriptor
##############
$_[KERNEL]->select_read( $inotify_FH, "inotify_poll" );
},
inotify_poll => sub {
$_[HEAP]{inotify}->poll;
},
watch_hdlr => \&watch_hdlr,
##############
# Process the next file in the queue
##############
task_next_file => \&task_next_file,
##############
# print the output of the job
##############
task_output => sub {
my $result = $_[ARG0];
print "$result\n";
},
##############
# When we are done with a file, go process the
# next file if there is one waiting
##############
task_done => sub {
my ($kernel, $heap, $task_id) = @_[ KERNEL, HEAP, ARG0 ];
delete $heap->{task}{$task_id};
$kernel->yield("task_next_file");
},
sig_child => sub {
my ($heap, $pid) = @_[ HEAP, ARG1 ];
my $details = delete $heap->{$pid};
},
},
);
POE::Kernel->run();
}
exit 0;
