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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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namespace core_cache;
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use core\exception\moodle_exception;
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/**
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* Cache Loader supporting locking.
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*
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* This interface should be given to classes already implementing core_cache\loader_interface that also wish to support locking.
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* It outlines the required structure for utilising locking functionality when using a cache.
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*
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* Can be implemented by any class already implementing the core_cache\loader_interface interface.
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* @package core_cache
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* @copyright Sam Hemelryk
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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interface loader_with_locking_interface {
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/**
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* Acquires a lock for the given key.
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*
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* Please note that this happens automatically if the cache definition requires locking.
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* it is still made a public method so that adhoc caches can use it if they choose.
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* However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure
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* locks are acquired, checked, and released.
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*
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* Prior to Moodle 4,3 this function used to return false if the lock cannot be obtained. It
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* now always returns true, and throws an exception if the lock cannot be obtained.
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*
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* @param string|int $key
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* @return bool Always returns true (for backwards compatibility)
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* @throws moodle_exception If the lock cannot be obtained after a timeout
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*/
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public function acquire_lock($key);
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/**
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* Checks if the cache loader owns the lock for the given key.
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*
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* Please note that this happens automatically if the cache definition requires locking.
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* it is still made a public method so that adhoc caches can use it if they choose.
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* However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure
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* locks are acquired, checked, and released.
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*
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* @param string|int $key
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* @return bool True if this code has the lock, false if there is a lock but this code doesn't have it,
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* null if there is no lock.
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*/
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public function check_lock_state($key);
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/**
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* Releases the lock for the given key.
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*
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* Please note that this happens automatically if the cache definition requires locking.
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* it is still made a public method so that adhoc caches can use it if they choose.
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* However this doesn't guarantee consistent access. It will become the responsibility of the calling code to ensure
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* locks are acquired, checked, and released.
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*
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* @param string|int $key
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* @return bool True if the lock has been released, false if there was a problem releasing the lock.
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*/
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public function release_lock($key);
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}
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// Alias this class to the old name.
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// This file will be autoloaded by the legacyclasses autoload system.
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// In future all uses of this class will be corrected and the legacy references will be removed.
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class_alias(loader_with_locking_interface::class, \cache_loader_with_locking::class);
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