locker(3)
NAME
IPC::Locker - Distributed lock handler
SYNOPSIS
use IPC::Locker;
my $lock = IPC::Locker->lock(lock=>'one_per_machine',
host=>'example.std.com',
port=>223);
if ($lock->lock()) { something; }
if ($lock->locked()) { something; }
$lock->unlock();
DESCRIPTION
"IPC::Locker" will query a remote server to obtain a lock.
This is useful for distributed utilities which run on many
machines, and cannot use file locks or other such mecha
nisms due to NFS or lack of common file systems.
- new ([parameter=>value ...]);
- Create a lock structure.
- lock ([parameter=>value ...]);
- Try to obtain the lock, return the lock object if suc
cessful, else undef. - locked ()
- Return true if the lock has been obtained.
- lock_name ()
- Return the name of the lock.
- unlock ()
- Remove the given lock. This will be called automati
cally when the object is destroyed. - break_lock ()
- Remove current locker for the given lock.
- owner ([parameter=>value ...]);
- Returns a string of who has the lock or undef if not
currently . Note that this information is not atomic,
and may change asyncronously; do not use this to tell
if the lock will be available, to do that, try to
obtain the lock and then release it if you got it.
PARAMETERS
- block
- Boolean flag, true indicates wait for the lock when
calling lock() and die if a error occurs. False indi
cates to just return false. Defaults to true. - family
- The family of transport to use, either INET or UNIX.
Defaults to INET. - host
- The name of the host containing the lock server. It
may also be a array of hostnames, where if the first
one is down, subsequent ones will be tried. - port
- The port number (INET) or name (UNIX) of the lock
server. Defaults to 'lockerd' looked up via /etc/ser
vices, else 1751. - lock
- The name of the lock. This may also be a reference to
an array of lock names, and the first free lock will
be returned. - print_broke
- A function to print a message when the lock is broken.
The only argument is self. Defaults to print a mes
sage if verbose is set. - print_obtained
- A function to print a message when the lock is
obtained after a delay. The only argument is self.
Defaults to print a message if verbose is set. - print_waiting
- A function to print a message when the lock is busy
and needs to be waited for. The first argument is
self, second the name of the lock. Defaults to print
a message if verbose is set. - print_down
- A function to print a message when the lock server is
unavailable. The first argument is self. Defaults to
a croak message. - timeout
- The maximum time in seconds that the lock may be held
before being forced open, passed to the server when
the lock is created. Thus if the requestor dies, the
lock will be released after that amount of time. Zero
disables the timeout. Defaults to 10 minutes. - user
- Name to request the lock under, defaults to
host_pid_user - autounlock
- True to cause the server to automatically timeout a
lock if the locking process has died. For the process
to be detected, it must be on the same host as either
the locker client (the host making the lock call), or
the locker server. Defaults false. - verbose
- True to print messages when waiting for locks.
Defaults false.
SEE ALSO
"lockerd",
DISTRIBUTION
This package is distributed via CPAN.
AUTHORS
- Wilson Snyder <wsnyder@wsnyder.org>