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module ZK
module Locker
# An exclusive lock implementation
#
# If the name 'dingus' is given, then in the case of an exclusive lock, the
# algorithm works like:
#
# * lock_path = `zk.create("/_zklocking/dingus/ex", :sequential => true, :ephemeral => true)`
# * extract the digit from the lock path
# * of all the children under '/_zklocking/dingus', do we have the lowest digit?
# * __yes__: then we hold the lock, if we're non-blocking, return true
# * __no__: is the lock blocking?
# * __yes__: then set a watch on the next-to-lowest node and sleep the current thread until that node has been deleted
# * __no__: return false, you lose
#
class ExclusiveLocker < LockerBase
# (see LockerBase#lock)
# obtain an exclusive lock.
#
def lock(opts={})
super
end
# (see LockerBase#assert!)
#
# checks that we:
#
# * we have obtained the lock (i.e. {#locked?} is true)
# * have a lock path
# * our lock path still exists
# * there are no locks, _exclusive or shared_, with lower numbers than ours
#
def assert!
super
end
# (see LockerBase#acquirable?)
def acquirable?
return true if locked?
stat = zk.stat(root_lock_path)
!stat.exists? or stat.num_children == 0
rescue Exceptions::NoNode # XXX: is this ever hit? stat shouldn't raise
true
end
private
# @private
def lock_prefix
EXCLUSIVE_LOCK_PREFIX
end
# @private
def blocking_locks
lower_lock_names
end
end # ExclusiveLocker
end # Locker
end # ZK
Version data entries
8 entries across 8 versions & 1 rubygems