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1 | 1 | Lockhandler |
2 | 2 | =========== |
| 3 | + |
| 4 | +..versionadded::2.6 |
| 5 | + The Lock handler feature was introduced in Symfony 2.6 |
| 6 | + |
| 7 | +What is a lock? |
| 8 | +--------------- |
| 9 | + |
| 10 | + In computer science, a lock is a synchronization mechanism for enforcing |
| 11 | + limits on access to a resource in an environment where there are many |
| 12 | + threads of execution. A lock is designed to enforce a mutual exclusion |
| 13 | + concurrency control policy. |
| 14 | + |
| 15 | + -- `Wikipedia`_ |
| 16 | + |
| 17 | +Usage |
| 18 | +----- |
| 19 | + |
| 20 | +..caution:: |
| 21 | + |
| 22 | + This lock handler works only when using one and only one host. If you have |
| 23 | + several hosts, you must not use this helper. |
| 24 | + |
| 25 | + |
| 26 | +A lock can be used, for example, to allow only one instance of a command to run. |
| 27 | + |
| 28 | + |
| 29 | +Usage:: |
| 30 | + |
| 31 | + use Symfony\Component\Filesystem\LockHandler; |
| 32 | + |
| 33 | + $lockHandler = new LockHelper('hello.lock'); |
| 34 | + if (!$lockHandler->lock()) { |
| 35 | + 'The resource "hello" is already locked by another process.'); |
| 36 | + |
| 37 | + return 0; |
| 38 | + } |
| 39 | + |
| 40 | +The first argument of the ``LockHelper`` is used to create a file on the local |
| 41 | +filesystem. By default, the LockHelper will create the file in the temporary |
| 42 | +directory. Another directory can be chosen by using the second argument. |
| 43 | + |
| 44 | +The ``lock`` method tries to acquire the lock. If the lock is acquired, the |
| 45 | +method returns ``true``, false otherwise. If the method ``lock`` method is |
| 46 | +called severals times it will always return ``true`` if the lack was acquired on |
| 47 | +the first call. |
| 48 | + |
| 49 | +The ``release`` method release the lock. So after the release, another process |
| 50 | +can lock the resource. The release is always released by PHP at the end of the |
| 51 | +script. |
| 52 | + |
| 53 | +.. _Wikipedia:http://en.wikipedia.org/wiki/Lock_%28computer_science%29 |