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LockManager.php
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LockManager.php
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<?php
/**
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use Wikimedia\RequestTimeout\RequestTimeout;
use Wikimedia\WaitConditionLoop;
/**
* @defgroup LockManager Lock management
* @ingroup FileBackend
*/
/**
* Resource locking handling.
*
* Locks on resource keys can either be shared or exclusive.
*
* Implementations must keep track of what is locked by this process
* in-memory and support nested locking calls (using reference counting).
* At least LOCK_UW and LOCK_EX must be implemented. LOCK_SH can be a no-op.
* Locks should either be non-blocking or have low wait timeouts.
*
* Subclasses should avoid throwing exceptions at all costs.
*
* @stable to extend
* @ingroup LockManager
* @since 1.19
*/
abstract class LockManager {
/** @var LoggerInterface */
protected $logger;
/** @var array Mapping of lock types to the type actually used */
protected $lockTypeMap = [
self::LOCK_SH => self::LOCK_SH,
self::LOCK_UW => self::LOCK_EX, // subclasses may use self::LOCK_SH
self::LOCK_EX => self::LOCK_EX
];
/** @var array Map of (resource path => lock type => count) */
protected $locksHeld = [];
/** @var string domain (usually wiki ID) */
protected $domain;
/** @var int maximum time locks can be held */
protected $lockTTL;
/** @var string Random 32-char hex number */
protected $session;
/** Lock types; stronger locks have higher values */
public const LOCK_SH = 1; // shared lock (for reads)
public const LOCK_UW = 2; // shared lock (for reads used to write elsewhere)
public const LOCK_EX = 3; // exclusive lock (for writes)
/** Max expected lock expiry in any context */
protected const MAX_LOCK_TTL = 2 * 3600; // 2 hours
/** Default lock TTL in CLI mode */
protected const CLI_LOCK_TTL = 3600; // 1 hour
/** Minimum lock TTL. The configured lockTTL is ignored if it is less than this value. */
protected const MIN_LOCK_TTL = 5; // seconds
/** The minimum lock TTL if it is guessed from max_execution_time rather than configured. */
protected const MIN_GUESSED_LOCK_TTL = 5 * 60; // 5 minutes
/**
* Construct a new instance from configuration
* @stable to call
*
* @param array $config Parameters include:
* - domain : Domain (usually wiki ID) that all resources are relative to [optional]
* - lockTTL : Age (in seconds) at which resource locks should expire.
* This only applies if locks are not tied to a connection/process.
*/
public function __construct( array $config ) {
$this->domain = $config['domain'] ?? 'global';
if ( isset( $config['lockTTL'] ) ) {
$this->lockTTL = max( self::MIN_LOCK_TTL, $config['lockTTL'] );
} elseif ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' ) {
$this->lockTTL = self::CLI_LOCK_TTL;
} else {
$ttl = 2 * ceil( RequestTimeout::singleton()->getWallTimeLimit() );
$this->lockTTL = ( $ttl === INF || $ttl < self::MIN_GUESSED_LOCK_TTL )
? self::MIN_GUESSED_LOCK_TTL : $ttl;
}
// Upper bound on how long to keep lock structures around. This is useful when setting
// TTLs, as the "lockTTL" value may vary based on CLI mode and app server group. This is
// a "safe" value that can be used to avoid clobbering other locks that use high TTLs.
$this->lockTTL = min( $this->lockTTL, self::MAX_LOCK_TTL );
$random = [];
for ( $i = 1; $i <= 5; ++$i ) {
$random[] = mt_rand( 0, 0xFFFFFFF );
}
$this->session = md5( implode( '-', $random ) );
$this->logger = $config['logger'] ?? new NullLogger();
}
/**
* Lock the resources at the given abstract paths
*
* @param array $paths List of resource names
* @param int $type LockManager::LOCK_* constant
* @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.21)
* @return StatusValue
*/
final public function lock( array $paths, $type = self::LOCK_EX, $timeout = 0 ) {
return $this->lockByType( [ $type => $paths ], $timeout );
}
/**
* Lock the resources at the given abstract paths
*
* @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
* @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.21)
* @return StatusValue
* @since 1.22
*/
final public function lockByType( array $pathsByType, $timeout = 0 ) {
$pathsByType = $this->normalizePathsByType( $pathsByType );
$status = null;
$loop = new WaitConditionLoop(
function () use ( &$status, $pathsByType ) {
$status = $this->doLockByType( $pathsByType );
return $status->isOK() ?: WaitConditionLoop::CONDITION_CONTINUE;
},
$timeout
);
$loop->invoke();
// @phan-suppress-next-line PhanTypeMismatchReturn WaitConditionLoop throws or status is set
return $status;
}
/**
* Unlock the resources at the given abstract paths
*
* @param array $paths List of paths
* @param int $type LockManager::LOCK_* constant
* @return StatusValue
*/
final public function unlock( array $paths, $type = self::LOCK_EX ) {
return $this->unlockByType( [ $type => $paths ] );
}
/**
* Unlock the resources at the given abstract paths
*
* @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
* @return StatusValue
* @since 1.22
*/
final public function unlockByType( array $pathsByType ) {
$pathsByType = $this->normalizePathsByType( $pathsByType );
$status = $this->doUnlockByType( $pathsByType );
return $status;
}
/**
* Get the base 36 SHA-1 of a string, padded to 31 digits.
* Before hashing, the path will be prefixed with the domain ID.
* This should be used internally for lock key or file names.
*
* @param string $path
* @return string
*/
final protected function sha1Base36Absolute( $path ) {
return Wikimedia\base_convert( sha1( "{$this->domain}:{$path}" ), 16, 36, 31 );
}
/**
* Normalize the $paths array by converting LOCK_UW locks into the
* appropriate type and removing any duplicated paths for each lock type.
*
* @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
* @return array
* @since 1.22
*/
final protected function normalizePathsByType( array $pathsByType ) {
$res = [];
foreach ( $pathsByType as $type => $paths ) {
foreach ( $paths as $path ) {
if ( (string)$path === '' ) {
throw new InvalidArgumentException( __METHOD__ . ": got empty path." );
}
}
$res[$this->lockTypeMap[$type]] = array_unique( $paths );
}
return $res;
}
/**
* @see LockManager::lockByType()
* @stable to override
* @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
* @return StatusValue
* @since 1.22
*/
protected function doLockByType( array $pathsByType ) {
$status = StatusValue::newGood();
$lockedByType = []; // map of (type => paths)
foreach ( $pathsByType as $type => $paths ) {
$status->merge( $this->doLock( $paths, $type ) );
if ( $status->isOK() ) {
$lockedByType[$type] = $paths;
} else {
// Release the subset of locks that were acquired
foreach ( $lockedByType as $lType => $lPaths ) {
$status->merge( $this->doUnlock( $lPaths, $lType ) );
}
break;
}
}
return $status;
}
/**
* Lock resources with the given keys and lock type
*
* @param array $paths List of paths
* @param int $type LockManager::LOCK_* constant
* @return StatusValue
*/
abstract protected function doLock( array $paths, $type );
/**
* @see LockManager::unlockByType()
* @stable to override
* @param array $pathsByType Map of LockManager::LOCK_* constants to lists of paths
* @return StatusValue
* @since 1.22
*/
protected function doUnlockByType( array $pathsByType ) {
$status = StatusValue::newGood();
foreach ( $pathsByType as $type => $paths ) {
$status->merge( $this->doUnlock( $paths, $type ) );
}
return $status;
}
/**
* Unlock resources with the given keys and lock type
*
* @param array $paths List of paths
* @param int $type LockManager::LOCK_* constant
* @return StatusValue
*/
abstract protected function doUnlock( array $paths, $type );
}

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