apache::session::lock::semaphore(3pm) [debian man page]

Apache::Session::Lock::Semaphore(3pm)			User Contributed Perl Documentation		     Apache::Session::Lock::Semaphore(3pm)

NAME

       Apache::Session::Lock::Semaphore - Provides mutual exclusion through semaphores

SYNOPSIS

	use Apache::Session::Lock::Semaphore;

	my $locker = new Apache::Session::Lock::Semaphore;
	die "no semaphores" unless $locker;

	$locker->acquire_read_lock($ref);
	$locker->acquire_write_lock($ref);
	$locker->release_read_lock($ref);
	$locker->release_write_lock($ref);
	$locker->release_all_locks($ref);

DESCRIPTION

       Apache::Session::Lock::semaphore fulfills the locking interface of Apache::Session.  Mutual exclusion is achieved through system semaphores
       and the IPC::Semaphore module.

CONFIGURATION

       The module must know how many semaphores to use, and what semaphore key to use. The number of semaphores has an impact on performance.
       More semaphores means less lock contention. You should use the maximum number of semaphores that your platform will allow. On stock NetBSD,
       OpenBSD, and Solaris systems, this is probably 16. On Linux 2.2, this is 32. This module tries to guess the number based on your operating
       system, but it is safer to configure it yourself.

       To set the number of semaphores, you need to pass an argument in the usual Apache::Session style. The name of the argument is NSems, and
       the value is an integer power of 2. For example:

	tie %s, 'Apache::Session::Blah', $id, {NSems => 16};

       You may also need to configure the semaphore key that this package uses. By default, it uses key 31818.	You can change this using the
       argument SemaphoreKey:

	tie %s, 'Apache::Session::Blah', $id, {NSems => 16, SemaphoreKey => 42};

PROBLEMS

       There are a few problems that people frequently encounter when using this package.

       If you get an invalid argument message, that usually means that the system is unhappy with the number of semaphores that you requested.
       Try decreasing the number of semaphores.  The semaphore blocks that this package creates are persistent until the system is rebooted, so if
       you request 8 semaphores one time and 16 semaphores the next, it won't work.  Use the system commands ipcs and ipcrm to inspect and remove
       unwanted semphore blocks.

   Cygwin
       IPC on Cygwin requires running cygserver. Without it, program will exit with "Bad System call" message. It cannot be intercepted with eval.

       Read /usr/share/doc/Cygwin/cygserver.README for more information.

   Darwin/MacOS X
       Darwin and MacOS X may not have semaphores, see <http://sysnet.ucsd.edu/~bellardo/darwin/sysvsem.html>

   *BSD
       Error "No space left on device" means that maximum number of semaphores is reached.  See
       <http://www.postgresql.org/docs/7.3/static/kernel-resources.html> for more information.

AUTHOR

       This module was written by Jeffrey William Baker <jwbaker@acm.org>.

SEE ALSO

       Apache::Session

perl v5.10.1							    2010-10-18				     Apache::Session::Lock::Semaphore(3pm)

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Apache::Session::Flex(3pm)				User Contributed Perl Documentation				Apache::Session::Flex(3pm)

NAME

       Apache::Session::Flex - Specify everything at runtime

SYNOPSIS

	use Apache::Session::Flex;

	tie %hash, 'Apache::Session::Flex', $id, {
	   Store     => 'DB_File',
	   Lock      => 'Null',
	   Generate  => 'MD5',
	   Serialize => 'Storable'
	};

	# or

	tie %hash, 'Apache::Session::Flex', $id, {
	   Store     => 'Postgres',
	   Lock      => 'Null',
	   Generate  => 'MD5',
	   Serialize => 'Base64'
	};

	# you decide!

DESCRIPTION

       This module is an implementation of Apache::Session.  Unlike other implementations, it allows you to specify the backing store, locking
       scheme, ID generator, and data serializer at runtime.  You do this by passing arguments in the usual Apache::Session style (see SYNOPSIS).
       You may use any of the modules included in this distribution, or a module of your own making.  If you wish to use a module of your own
       making, you should make sure that it is available under the Apache::Session package namespace.

USAGE

       You pass the modules you want to use as arguments to the constructor.  The Apache::Session::Whatever part is appended for you: you should
       not supply it.  For example, if you wanted to use MySQL as the backing store, you should give the argument "Store =" 'MySQL'>, and not
       "Store =" 'Apache::Session::Store::MySQL'>.  There are four modules that you need to specify.  Store is the backing store to use.  Lock is
       the locking scheme.  Generate is the ID generation module.  Serialize is the data serialization module.

       There are many modules included in this distribution.  For each role, they are:

	Store:
	   MySQL
	   Postgres
	   DB_File
	   File

	Lock:
	   Null
	   MySQL
	   Semaphore

	Generate:
	   MD5

	Serialize:
	   Storable
	   Base64
	   UUEncode

       In addition to the arguments needed by this module, you must provide whatever arguments are expected by the backing store and lock manager
       that you are using.  Please see the documentation for those modules.

AUTHOR

       This module was written by Jeffrey William Baker <jwbaker@acm.org>.

SEE ALSO

       Apache::Session::File, Apache::Session::DB_File, Apache::Session::MySQL, Apache::Session::Postgres, Apache::Session

perl v5.10.1							    2010-10-18						Apache::Session::Flex(3pm)

Linux and UNIX Man Pages

apache::session::lock::semaphore(3pm) [debian man page]

Check Out this Related Man Page