NAME
Lock::Server - Light-weight RESTful socket based resource locking manager.
DESCRIPTION
This creates a socket server that handles lock and
unlock requests. The lock requests only return once a lock is
obtained or a timeout has occurred. A lock may only be locked
for a specific amount of time before the lock is timed out.
The protocol used is RESTFUL HTTP though the helper class wraps
that. It uses the GET verb with the following paths :
* CHECK/key - returns 1 if the key in question is currently locked
returns 0 if not
* LOCK/key/requester - returns lock expire time or 0
if there was an error
* UNLOCK/key/requester - returns 1 if the unlock went as expected,
0 otherwise
* VERIFY/key/requester - returns 1 if the key is locked to the
requester and did not time out and 0
otherwise.
* PING - returns 1 if the server is active
* SHUTDOWN - stops this LockServer
This does not do deadlock detection, relying on the timeouts to
prevent the system from getting in a hopelessly tangled state.
Care should be taken, as with any resource locking system, with
the use of Lock::Server. Adjust the timeouts for what makes sense
with the system you are designing. The lock requests return with the
time that the lock will expire.
SYNPOSIS
use Lock::Server;
use Lock::Server::Client;
my $lockServer = new Lock::Server( {
lock_timeout => 10, #seconds. default is 3
lock_attempt_timeout => 12, #seconds. default is 4
port => 888, #default is 8004
host => 'localhost', #default 127.0.0.1
} );
if( my $childPid = $lockServer->start ) {
print "Lock server started in child thread $childPid\n";
}
my $optional_args = { reconnect_attempts => 3, time_between_attempts => 1 };
my $lockClient_A = $lockServer->client( "CLIENT_A", $optional_args );
my $lockClient_B =
new Lock::Server::Client( "CLIENT_B", 'localhost', 888, $optional_args );
if( $lockClient_A->lock( "KEYA" ) ) {
print "Lock Successfull for locker A and KEYA\n";
} else {
print "Could not obtain lock in 12 seconds.\n";
}
# KEYA for LockerI times out after 10 seconds.
# Lock Client B waits until it can obtain the lock
if( $lockClient_B->lock( "KEYA" ) ) {
print "Lock Successfull for Client B lock 'KEYA'\n";
} else {
print "Could not obtain lock in 12 seconds.\n";
}
# KEYA for LockerII is now freed. The next locker
# attempting to lock KEYA will then obtain the lock.
if( $lockClientB->unlock( "KEYA" ) ) {
print "Unlock Successfull\n";
}
if( $lockServer->stop ) {
print "Lock server shut down.\n";
}
METHODS
Lock::Server::new( $args )
Creates a new lock server for the given optional arguments.
Arguments are :
* port - port to serve on. Defaults to 8004
* lock_timeout - low long should a lock last in seconds
* lock_attempt_timeout - how long should a requester
wait for a lock in seconds
* allow_shutdown - allows a client to shut the server down
* reconnect_attempts - if port is busy when starting the server
how many retries to connect before giving up and failing startup
* time_between_attempts - interval between reconnection attempts
client( lockername )
Returns a client with the given name that can send lock and unlock requests for keys.
ping
Returns '1' if this lock server is up and running
stop
Kills the lock server, breaking off any connections that are waiting for a lock.
start
Starts the lock server in a child process, opening up a
tcpip socket and returning the child pid or 0 if there
was an error.
run
Runs the lock server.
Helper package
NAME
Lock::Server::Client - client for locking server.
DESCRIPTION
Sends request to a Lock::Server to lock, unlock and check locks.
METHODS
new( lockername, host, port )
Creates a client object with the given name for the host and port.
isLocked( key )
Returns true if the key is locked by anyone.
lockedByMe( key )
Returns true if the key is locked by this client or
anyone with the name of this client. The name was given in the constructor.
lock( key )
Attempt to get the lock for the given key. Returns true if the lock
was obtained.
unlock( key )
Attempt to get unlock the given key. Returns true if the
key was locked to this client ( or someting with the same name ).
AUTHOR
Eric Wolf coyocanid@gmail.com
COPYRIGHT AND LICENSE
Copyright (c) 2015 Eric Wolf. All rights reserved. This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
VERSION
Version 1.71 (June 1, 2016))