NAME

       Mojo::IOLoop::ReadWriteProcess::Shared::Lock - IPC Lock

SYNOPSIS

           use Mojo::IOLoop::ReadWriteProcess qw(process queue lock);

           my $q = queue; # Create a Queue
           $q->pool->maximum_processes(10); # 10 Concurrent processes at maximum
           $q->queue->maximum_processes(50); # 50 is maximum total to be allowed in the queue

           $q->add(
             process(
               sub {
                 my $l = lock(key => 42); # IPC Lock
                 my $e = 1;
                 if ($l->lock) { # Blocking lock acquire
                   # Critical section
                   $e = 0;
                   $l->unlock;
                 }
                 exit($e);
               }
             )->set_pipes(0)->internal_pipes(0)) for 1 .. 20; # Fill with 20 processes

           $q->consume(); # Consume the processes

DESCRIPTION

       Mojo::IOLoop::ReadWriteProcess::Shared::Lock uses IPC::Semaphore internally and creates a
       Lock from a semaphore that is available across different processes.

METHODS

       Mojo::IOLoop::ReadWriteProcess::Shared::Lock inherits all events from
       Mojo::IOLoop::ReadWriteProcess::Shared::Semaphore and implements the following new ones.

   lock/unlock
           use Mojo::IOLoop::ReadWriteProcess qw(lock);

           my $l = lock(key => "42"); # Create Lock with key 42

           if ($l->lock) { # Blocking call
             # Critical section
             ...

             $l->unlock; # Release the lock
           }

       Acquire access to the lock and unlocks it.

       "lock()" has the same arguments as Mojo::IOLoop::ReadWriteProcess::Shared::Semaphore
       "acquire()".

   try_lock
           use Mojo::IOLoop::ReadWriteProcess qw(lock);

           my $l = lock(key => "42"); # Create Lock with key 42

           if ($l->try_lock) { # Non Blocking call
             # Critical section
             ...

             $l->unlock; # Release the lock
           }

       Try to acquire lock in a non-blocking way.

   lock_section
           use Mojo::IOLoop::ReadWriteProcess qw(lock);
           my $l = lock(key => 3331);
           my $e = 1;
           $l->lock_section(sub { $e = 0; die; }); # or also $l->section(sub { $e = 0 });

           $l->locked; # is 0

       Executes a function inside a locked section. Errors are caught so lock is released in case
       of failures.

ATTRIBUTES

       Mojo::IOLoop::ReadWriteProcess::Shared::Lock inherits all attributes from
       Mojo::IOLoop::ReadWriteProcess::Shared::Semaphore and provides the following new ones.

   flags
           use Mojo::IOLoop::ReadWriteProcess qw(lock);
           use IPC::SysV qw(IPC_CREAT IPC_EXCL S_IRUSR S_IWUSR);

           my $l = lock(flags=> IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR);

       Sets flag for the lock. In such way you can limit the access to the lock, e.g. to specific
       user/group process.

   key
           use Mojo::IOLoop::ReadWriteProcess qw(lock);
           my $l = lock(key => 42);

       Sets the lock key that is used to retrieve the lock among different processes, must be an
       integer.

   locked
           use Mojo::IOLoop::ReadWriteProcess qw(lock);

           my $l = lock(key => 42);

           $l->lock_section(sub {
             $l->locked; # 1
           });

           $l->locked; # 0

       Returns the lock status

DEBUGGING

       You can set MOJO_PROCESS_DEBUG environment variable to get diagnostics about the process
       execution.

           MOJO_PROCESS_DEBUG=1

LICENSE

       Copyright (C) Ettore Di Giacinto.

       This library is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.

AUTHOR

       Ettore Di Giacinto <edigiacinto@suse.com>

perl v5.34.0                                2022Mojo::IOLoop::ReadWriteProcess::Shared::Lock(3pm)