Class: ZK::Locker::Semaphore
- Inherits:
-
LockerBase
- Object
- LockerBase
- ZK::Locker::Semaphore
- Includes:
- Exceptions
- Defined in:
- lib/zk/locker/semaphore.rb
Overview
A semaphore implementation
Class Attribute Summary collapse
-
.default_root_node ⇒ Object
the default root path we will use when a value is not given to a constructor.
Attributes inherited from LockerBase
Instance Method Summary collapse
-
#acquirable? ⇒ Object
- If this instance holds the lock is true we return true (as we have already succeeded in acquiring the lock) * If this instance doesn't hold the lock, we'll do a check on the server to see if there are any participants who hold the lock and would prevent us from acquiring the lock.
-
#assert! ⇒ Object
This is for users who wish to check that the assumption is correct that they actually still hold the lock.
- #blocked_by_semaphore? ⇒ Boolean
- #got_semaphore? ⇒ Boolean (also: #got_lock?)
-
#initialize(client, name, semaphore_size, root_node = nil) ⇒ Semaphore
constructor
A new instance of Semaphore.
-
#lock(opts = {}) ⇒ true, ...
obtain a shared lock.
Methods inherited from LockerBase
#assert, #lock!, #lock_basename, #locked?, #unlock, #unlock!, #with_lock
Methods included from ZK::Logging
Constructor Details
#initialize(client, name, semaphore_size, root_node = nil) ⇒ Semaphore
Returns a new instance of Semaphore.
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# File 'lib/zk/locker/semaphore.rb', line 15 def initialize(client, name, semaphore_size, root_node=nil) raise BadArgument, <<-EOMESSAGE unless semaphore_size.kind_of? Integer semaphore_size must be Integer, not #{semaphore_size.inspect} EOMESSAGE @semaphore_size = semaphore_size super(client, name, root_node || ::ZK::Locker::Semaphore.default_root_node) end |
Class Attribute Details
.default_root_node ⇒ Object
the default root path we will use when a value is not given to a constructor
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# File 'lib/zk/locker/semaphore.rb', line 12 def default_root_node @default_root_node end |
Instance Method Details
#acquirable? ⇒ Object
It should be obvious, but there is no way to guarantee that between the time this method checks the server and taking any action to acquire the lock, another client may grab the lock before us (or converseley, another client may release the lock). This is simply meant as an advisory, and may be useful in some cases.
- If this instance holds the lock is true we return true (as we have already succeeded in acquiring the lock)
- If this instance doesn't hold the lock, we'll do a check on the server
to see if there are any participants who hold the lock and would
prevent us from acquiring the lock.
- If this instance could acquire the lock we will return true.
- If another client would prevent us from acquiring the lock, we return false.
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# File 'lib/zk/locker/semaphore.rb', line 46 def acquirable? return true if locked? return false if blocked_by_semaphore? true rescue Exceptions::NoNode true end |
#assert! ⇒ Object
This is for users who wish to check that the assumption is correct that they actually still hold the lock. (check for session interruption, perhaps a lock is obtained in one method and handed to another)
This, unlike LockerBase#locked? will actually go and check the conditions that constitute "holding the lock" with the server.
checks that we:
- we have obtained the lock (i.e. LockerBase#locked? is true)
- have a lock path
- our lock path still exists
- there are no exclusive locks with lower numbers than ours
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# File 'lib/zk/locker/semaphore.rb', line 41 def assert! super end |
#blocked_by_semaphore? ⇒ Boolean
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# File 'lib/zk/locker/semaphore.rb', line 54 def blocked_by_semaphore? ( blocking_locks.size >= @semaphore_size ) end |
#got_semaphore? ⇒ Boolean Also known as: got_lock?
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# File 'lib/zk/locker/semaphore.rb', line 73 def got_semaphore? synchronize { lock_path and not blocked_by_semaphore? } end |
#lock(blocking = false) ⇒ true, ... #lock(opts = {}) ⇒ true, ...
obtain a shared lock.
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# File 'lib/zk/locker/semaphore.rb', line 28 def lock(opts={}) super end |