From cc8532af66c44667b0ef5fb1f85bf8be728db27b Mon Sep 17 00:00:00 2001
From: Tomas Cohen Arazi <tomascohen@theke.io>
Date: Fri, 10 Apr 2020 19:37:31 -0300
Subject: [PATCH] Bug 25109: Add ->new and ->lock_exec to Koha::Script

---
 Koha/Script.pm  | 97 +++++++++++++++++++++++++++++++++++++++++++++++++
 t/Koha/Script.t | 27 +++++++++++++-
 t/Koha/sleep.pl | 19 ++++++++++
 3 files changed, 142 insertions(+), 1 deletion(-)
 create mode 100755 t/Koha/sleep.pl

diff --git a/Koha/Script.pm b/Koha/Script.pm
index 2126d18506..9cfbc9ecf8 100644
--- a/Koha/Script.pm
+++ b/Koha/Script.pm
@@ -35,7 +35,12 @@ This class should be used in all scripts. It sets the interface and userenv appr
 
 =cut
 
+use File::Basename;
+use Fcntl qw(:flock);
+
 use C4::Context;
+use Koha::Exceptions;
+use Koha::Exceptions::Exception;
 
 sub import {
     my $class = shift;
@@ -67,6 +72,98 @@ sub import {
     }
 }
 
+=head1 API
+
+=head2 Class methods
+
+=head3 new
+
+    my $script = Koha::Script->new(
+        {
+            script    => $0, # mandatory
+          [ lock_name => 'my_script' ]
+        }
+    );
+
+Create a new Koha::Script object. The I<script> parameter is mandatory,
+and will usually be passed I<$0> in the caller script. The I<lock_name>
+parameter is optional, and is used to generate the lock file if passed.
+
+=cut
+
+sub new {
+    my ($class, $params) = @_;
+    my $script   = $params->{script};
+
+    Koha::Exceptions::MissingParameter->throw(
+        "The 'script' parameter is mandatory. You should usually pass \$0"
+    ) unless $script;
+
+    my $self = { script => $script };
+    $self->{lock_name} = $params->{lock_name}
+        if exists $params->{lock_name} and $params->{lock_name};
+
+    bless $self, $class;
+    return $self;
+}
+
+=head3 lock_exec
+
+    # die if cannot get the lock
+    try {
+        $script->lock_exec;
+    }
+    catch {
+        die "$_";
+    };
+
+    # wait for the lock to be released
+    $script->lock_exec({ wait => 1 });
+
+This method sets an execution lock to prevent concurrent execution of the caller
+script. If passed the I<wait> parameter with a true value, it will make the caller
+wait until it can be granted the lock (flock's LOCK_NB behaviour). It will
+otherwise throw an exception immediately.
+
+=cut
+
+sub lock_exec {
+    my ($self, $params) = @_;
+
+    $self->_initialize_locking
+        unless $self->{lock_file};
+
+    my $lock_params = ($params->{wait}) ? LOCK_EX : LOCK_EX | LOCK_NB;
+
+    open our $lock_handle, '>', $self->{lock_file}
+        or Koha::Exceptions::Exception->throw("Unable to open the lock file ".$self->{lock_file}.": $!");
+    $self->{lock_handle} = $lock_handle;
+    flock( $lock_handle, $lock_params )
+        or Koha::Exceptions::Exception->throw("Unable to acquire the lock ".$self->{lock_file}.": $!");
+}
+
+=head2 Internal methods
+
+=head3 _initialize_locking
+
+    $self->_initialize_locking
+
+This method initializes the locking configuration.
+
+=cut
+
+sub _initialize_locking {
+    my ($self) = @_;
+
+    my $lock_dir = C4::Context->config('lock_dir')
+        // C4::Context->temporary_directory();
+
+    my $lock_name = $self->{lock_name} // fileparse( $self->{script} );
+    $self->{lock_file} = "$lock_dir/$lock_name";
+
+    return $self;
+}
+
 =head1 AUTHOR
 
 Martin Renvoize <martin.renvoize@ptfs-europe.com>
diff --git a/t/Koha/Script.t b/t/Koha/Script.t
index 778693b607..b5853282e8 100644
--- a/t/Koha/Script.t
+++ b/t/Koha/Script.t
@@ -17,10 +17,13 @@
 
 use Modern::Perl;
 
-use Test::More tests => 3;
+use Test::More tests => 4;
+use Test::Exception;
 
 BEGIN { use_ok('Koha::Script') }
 
+use File::Basename;
+
 use C4::Context;
 
 my $userenv = C4::Context->userenv;
@@ -44,4 +47,26 @@ is_deeply(
 my $interface = C4::Context->interface;
 is( $interface, 'commandline', "Context interface set correctly with no flags" );
 
+subtest 'lock_exec() tests' => sub {
+    plan tests => 2;
+
+    # Launch the sleep script
+    my $pid = fork();
+    if ( $pid == 0 ) {
+        system( dirname(__FILE__) . '/sleep.pl 2>&1' );
+        exit;
+    }
+
+    sleep 1; # Make sure we start after the fork
+    my $command = dirname(__FILE__) . '/sleep.pl';
+    my $result  = `$command 2>&1`;
+
+    like( $result, qr{Unable to acquire the lock.*}, 'Exception found' );
+
+    throws_ok
+        { Koha::Script->new({ lock_name => 'blah' }); }
+        'Koha::Exceptions::MissingParameter',
+        'Not passing the "script" parameter makes it raise an exception';
+};
+
 1;
diff --git a/t/Koha/sleep.pl b/t/Koha/sleep.pl
new file mode 100755
index 0000000000..009b4034dc
--- /dev/null
+++ b/t/Koha/sleep.pl
@@ -0,0 +1,19 @@
+#!/usr/bin/perl
+
+use Modern::Perl;
+
+use Koha::Script;
+use Fcntl qw(:flock);
+use Try::Tiny;
+
+# # Lock execution
+my $script = Koha::Script->new({ script => 'sleep.pl' });
+
+$script->lock_exec;
+
+# Sleep for a while, we need to force the concurrent access to the
+# lock file
+sleep 2;
+
+# Normal exit
+1;
-- 
2.26.0