--- /dev/null
+<?php
+/**
+ * @defgroup LockManager Lock management
+ * @ingroup FileBackend
+ */
+use Psr\Log\LoggerInterface;
+use Wikimedia\WaitConditionLoop;
+
+/**
+ * Resource locking handling.
+ *
+ * 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
+ * @ingroup LockManager
+ */
+
+/**
+ * @brief Class for handling resource locking.
+ *
+ * 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.
+ *
+ * @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 = [];
+
+ protected $domain; // string; domain (usually wiki ID)
+ protected $lockTTL; // integer; maximum time locks can be held
+
+ /** @var string Random 32-char hex number */
+ protected $session;
+
+ /** Lock types; stronger locks have higher values */
+ const LOCK_SH = 1; // shared lock (for reads)
+ const LOCK_UW = 2; // shared lock (for reads used to write elsewhere)
+ const LOCK_EX = 3; // exclusive lock (for writes)
+
+ /** @var int Max expected lock expiry in any context */
+ const MAX_LOCK_TTL = 7200; // 2 hours
+
+ /**
+ * Construct a new instance from configuration
+ *
+ * @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 = isset( $config['domain'] ) ? $config['domain'] : 'global';
+ if ( isset( $config['lockTTL'] ) ) {
+ $this->lockTTL = max( 5, $config['lockTTL'] );
+ } elseif ( PHP_SAPI === 'cli' ) {
+ $this->lockTTL = 3600;
+ } else {
+ $met = ini_get( 'max_execution_time' ); // this is 0 in CLI mode
+ $this->lockTTL = max( 5 * 60, 2 * (int)$met );
+ }
+
+ // 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 = isset( $config['logger'] ) ? $config['logger'] : new \Psr\Log\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();
+
+ 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 );
+ }
+
+ /**
+ * Get the base 16 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 sha1Base16Absolute( $path ) {
+ return sha1( "{$this->domain}:{$path}" );
+ }
+
+ /**
+ * 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 ) {
+ $res[$this->lockTypeMap[$type]] = array_unique( $paths );
+ }
+
+ return $res;
+ }
+
+ /**
+ * @see LockManager::lockByType()
+ * @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()
+ * @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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