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Apache::Session::Lock::File - Provides mutual exclusion using flock
use Apache::Session::Lock::File; my $locker = new Apache::Session::Lock::File; $locker->acquire_read_lock($ref); $locker->acquire_write_lock($ref); $locker->release_read_lock($ref); $locker->release_write_lock($ref); $locker->release_all_locks($ref);
$locker->clean($dir, $age);
Apache::Session::Lock::File fulfills the locking interface of
Apache::Session. Mutual exclusion is achieved through the use of temporary
files and the flock function.
The module must know where to create its temporary files. You must pass an argument in the usual Apache::Session style. The name of the argument is LockDirectory and its value is the path where you want the lockfiles created. Example:
tie %s, 'Apache::Session::Blah', $id, {LockDirectory => '/var/lock/sessions'}
If you do not supply this argument, temporary files will be created in /tmp.
This module does not unlink temporary files, because it interferes with proper
locking. This can cause problems on certain systems (Linux) whose file systems
(ext2) do not perform well with lots of files in one directory. To prevent this
you should use a script to clean out old files from your lock directory.
The meaning of old is left as a policy decision for the implementor, but a
method is provided for implementing that policy. You can use the clean
method of this module to remove files unmodified in the last $age seconds.
Example:
my $l = new Apache::Session::Lock::File;
$l->clean('/var/lock/sessions', 3600) #remove files older than 1 hour
Will do nothing if write lock is in effect, only set readlock flag to true.
Will do nothing if write lock is in effect, only set readlock flag to false.
Windows cannot escalate lock, so all locks will be exclusive.
release_read_lock not supported - it is not used by Apache::Session.
When deleting files, they are not locked (Win32 only).
This module was written by Jeffrey William Baker <jwbaker@acm.org>.