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Diffstat (limited to 'includes/libs/objectcache/BagOStuff.php')
| -rw-r--r-- | includes/libs/objectcache/BagOStuff.php | 438 |
1 files changed, 438 insertions, 0 deletions
diff --git a/includes/libs/objectcache/BagOStuff.php b/includes/libs/objectcache/BagOStuff.php new file mode 100644 index 00000000..0b791e5a --- /dev/null +++ b/includes/libs/objectcache/BagOStuff.php @@ -0,0 +1,438 @@ +<?php +/** + * Classes to cache objects in PHP accelerators, SQL database or DBA files + * + * Copyright © 2003-2004 Brion Vibber <brion@pobox.com> + * https://www.mediawiki.org/ + * + * 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 Cache + */ + +/** + * @defgroup Cache Cache + */ + +use Psr\Log\LoggerAwareInterface; +use Psr\Log\LoggerInterface; +use Psr\Log\NullLogger; + +/** + * interface is intended to be more or less compatible with + * the PHP memcached client. + * + * backends for local hash array and SQL table included: + * <code> + * $bag = new HashBagOStuff(); + * $bag = new SqlBagOStuff(); # connect to db first + * </code> + * + * @ingroup Cache + */ +abstract class BagOStuff implements LoggerAwareInterface { + private $debugMode = false; + + protected $lastError = self::ERR_NONE; + + /** + * @var LoggerInterface + */ + protected $logger; + + /** Possible values for getLastError() */ + const ERR_NONE = 0; // no error + const ERR_NO_RESPONSE = 1; // no response + const ERR_UNREACHABLE = 2; // can't connect + const ERR_UNEXPECTED = 3; // response gave some error + + public function __construct( array $params = array() ) { + if ( isset( $params['logger'] ) ) { + $this->setLogger( $params['logger'] ); + } else { + $this->setLogger( new NullLogger() ); + } + } + + /** + * @param LoggerInterface $logger + * @return null + */ + public function setLogger( LoggerInterface $logger ) { + $this->logger = $logger; + } + + /** + * @param bool $bool + */ + public function setDebug( $bool ) { + $this->debugMode = $bool; + } + + /** + * Get an item with the given key. Returns false if it does not exist. + * @param string $key + * @param mixed $casToken [optional] + * @return mixed Returns false on failure + */ + abstract public function get( $key, &$casToken = null ); + + /** + * Set an item. + * @param string $key + * @param mixed $value + * @param int $exptime Either an interval in seconds or a unix timestamp for expiry + * @return bool Success + */ + abstract public function set( $key, $value, $exptime = 0 ); + + /** + * Delete an item. + * @param string $key + * @return bool True if the item was deleted or not found, false on failure + */ + abstract public function delete( $key ); + + /** + * Merge changes into the existing cache value (possibly creating a new one). + * The callback function returns the new value given the current value (possibly false), + * and takes the arguments: (this BagOStuff object, cache key, current value). + * + * @param string $key + * @param callable $callback Callback method to be executed + * @param int $exptime Either an interval in seconds or a unix timestamp for expiry + * @param int $attempts The amount of times to attempt a merge in case of failure + * @return bool Success + */ + public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) { + if ( !is_callable( $callback ) ) { + throw new Exception( "Got invalid callback." ); + } + + return $this->mergeViaLock( $key, $callback, $exptime, $attempts ); + } + + /** + * @see BagOStuff::merge() + * + * @param string $key + * @param callable $callback Callback method to be executed + * @param int $exptime Either an interval in seconds or a unix timestamp for expiry + * @param int $attempts The amount of times to attempt a merge in case of failure + * @return bool Success + */ + protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10 ) { + do { + $casToken = null; // passed by reference + $currentValue = $this->get( $key, $casToken ); + // Derive the new value from the old value + $value = call_user_func( $callback, $this, $key, $currentValue ); + + if ( $value === false ) { + $success = true; // do nothing + } elseif ( $currentValue === false ) { + // Try to create the key, failing if it gets created in the meantime + $success = $this->add( $key, $value, $exptime ); + } else { + // Try to update the key, failing if it gets changed in the meantime + $success = $this->cas( $casToken, $key, $value, $exptime ); + } + } while ( !$success && --$attempts ); + + return $success; + } + + /** + * Check and set an item + * + * @param mixed $casToken + * @param string $key + * @param mixed $value + * @param int $exptime Either an interval in seconds or a unix timestamp for expiry + * @return bool Success + */ + protected function cas( $casToken, $key, $value, $exptime = 0 ) { + throw new Exception( "CAS is not implemented in " . __CLASS__ ); + } + + /** + * @see BagOStuff::merge() + * + * @param string $key + * @param callable $callback Callback method to be executed + * @param int $exptime Either an interval in seconds or a unix timestamp for expiry + * @param int $attempts The amount of times to attempt a merge in case of failure + * @return bool Success + */ + protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10 ) { + if ( !$this->lock( $key, 6 ) ) { + return false; + } + + $currentValue = $this->get( $key ); + // Derive the new value from the old value + $value = call_user_func( $callback, $this, $key, $currentValue ); + + if ( $value === false ) { + $success = true; // do nothing + } else { + $success = $this->set( $key, $value, $exptime ); // set the new value + } + + if ( !$this->unlock( $key ) ) { + // this should never happen + trigger_error( "Could not release lock for key '$key'." ); + } + + return $success; + } + + /** + * @param string $key + * @param int $timeout Lock wait timeout [optional] + * @param int $expiry Lock expiry [optional] + * @return bool Success + */ + public function lock( $key, $timeout = 6, $expiry = 6 ) { + $this->clearLastError(); + $timestamp = microtime( true ); // starting UNIX timestamp + if ( $this->add( "{$key}:lock", 1, $expiry ) ) { + return true; + } elseif ( $this->getLastError() ) { + return false; + } + + $uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us) + $sleep = 2 * $uRTT; // rough time to do get()+set() + + $locked = false; // lock acquired + $attempts = 0; // failed attempts + do { + if ( ++$attempts >= 3 && $sleep <= 5e5 ) { + // Exponentially back off after failed attempts to avoid network spam. + // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts. + $sleep *= 2; + } + usleep( $sleep ); // back off + $this->clearLastError(); + $locked = $this->add( "{$key}:lock", 1, $expiry ); + if ( $this->getLastError() ) { + return false; + } + } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout ); + + return $locked; + } + + /** + * @param string $key + * @return bool Success + */ + public function unlock( $key ) { + return $this->delete( "{$key}:lock" ); + } + + /** + * Delete all objects expiring before a certain date. + * @param string $date The reference date in MW format + * @param callable|bool $progressCallback Optional, a function which will be called + * regularly during long-running operations with the percentage progress + * as the first parameter. + * + * @return bool Success, false if unimplemented + */ + public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) { + // stub + return false; + } + + /* *** Emulated functions *** */ + + /** + * Get an associative array containing the item for each of the keys that have items. + * @param array $keys List of strings + * @return array + */ + public function getMulti( array $keys ) { + $res = array(); + foreach ( $keys as $key ) { + $val = $this->get( $key ); + if ( $val !== false ) { + $res[$key] = $val; + } + } + return $res; + } + + /** + * Batch insertion + * @param array $data $key => $value assoc array + * @param int $exptime Either an interval in seconds or a unix timestamp for expiry + * @return bool Success + * @since 1.24 + */ + public function setMulti( array $data, $exptime = 0 ) { + $res = true; + foreach ( $data as $key => $value ) { + if ( !$this->set( $key, $value, $exptime ) ) { + $res = false; + } + } + return $res; + } + + /** + * @param string $key + * @param mixed $value + * @param int $exptime + * @return bool Success + */ + public function add( $key, $value, $exptime = 0 ) { + if ( $this->get( $key ) === false ) { + return $this->set( $key, $value, $exptime ); + } + return false; // key already set + } + + /** + * Increase stored value of $key by $value while preserving its TTL + * @param string $key Key to increase + * @param int $value Value to add to $key (Default 1) + * @return int|bool New value or false on failure + */ + public function incr( $key, $value = 1 ) { + if ( !$this->lock( $key ) ) { + return false; + } + $n = $this->get( $key ); + if ( $this->isInteger( $n ) ) { // key exists? + $n += intval( $value ); + $this->set( $key, max( 0, $n ) ); // exptime? + } else { + $n = false; + } + $this->unlock( $key ); + + return $n; + } + + /** + * Decrease stored value of $key by $value while preserving its TTL + * @param string $key + * @param int $value + * @return int + */ + public function decr( $key, $value = 1 ) { + return $this->incr( $key, - $value ); + } + + /** + * Increase stored value of $key by $value while preserving its TTL + * + * This will create the key with value $init and TTL $ttl if not present + * + * @param string $key + * @param int $ttl + * @param int $value + * @param int $init + * @return bool + * @since 1.24 + */ + public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) { + return $this->incr( $key, $value ) || + $this->add( $key, (int)$init, $ttl ) || $this->incr( $key, $value ); + } + + /** + * Get the "last error" registered; clearLastError() should be called manually + * @return int ERR_* constant for the "last error" registry + * @since 1.23 + */ + public function getLastError() { + return $this->lastError; + } + + /** + * Clear the "last error" registry + * @since 1.23 + */ + public function clearLastError() { + $this->lastError = self::ERR_NONE; + } + + /** + * Set the "last error" registry + * @param int $err ERR_* constant + * @since 1.23 + */ + protected function setLastError( $err ) { + $this->lastError = $err; + } + + /** + * @param string $text + */ + protected function debug( $text ) { + if ( $this->debugMode ) { + $this->logger->debug( "{class} debug: $text", array( + 'class' => get_class( $this ), + ) ); + } + } + + /** + * Convert an optionally relative time to an absolute time + * @param int $exptime + * @return int + */ + protected function convertExpiry( $exptime ) { + if ( ( $exptime != 0 ) && ( $exptime < 86400 * 3650 /* 10 years */ ) ) { + return time() + $exptime; + } else { + return $exptime; + } + } + + /** + * Convert an optionally absolute expiry time to a relative time. If an + * absolute time is specified which is in the past, use a short expiry time. + * + * @param int $exptime + * @return int + */ + protected function convertToRelative( $exptime ) { + if ( $exptime >= 86400 * 3650 /* 10 years */ ) { + $exptime -= time(); + if ( $exptime <= 0 ) { + $exptime = 1; + } + return $exptime; + } else { + return $exptime; + } + } + + /** + * Check if a value is an integer + * + * @param mixed $value + * @return bool + */ + protected function isInteger( $value ) { + return ( is_int( $value ) || ctype_digit( $value ) ); + } +} |