bfef92cf98
This can be used by WANObjectCache or statsd metrics to estimate the size of objects and network commands without having to do an extra serialization round. Change-Id: I7b1b787bba39a21e2e04262e77ee7ae24e88f8ca
259 lines
8.1 KiB
PHP
259 lines
8.1 KiB
PHP
<?php
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/**
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* This program 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 2 of the License, or
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* (at your option) any later version.
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*
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* This program 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 along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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* @ingroup Cache
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*/
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use Wikimedia\ObjectFactory;
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/**
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* A cache class that directs writes to one set of servers and reads to
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* another. This assumes that the servers used for reads are setup to replica DB
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* those that writes go to. This can easily be used with redis for example.
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*
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* In the WAN scenario (e.g. multi-datacenter case), this is useful when
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* writes are rare or they usually take place in the primary datacenter.
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*
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* @ingroup Cache
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* @since 1.26
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*/
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class ReplicatedBagOStuff extends BagOStuff {
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/** @var BagOStuff */
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private $writeStore;
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/** @var BagOStuff */
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private $readStore;
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/** @var int Seconds to read from the master source for a key after writing to it */
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private $consistencyWindow;
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/** @var float[] Map of (key => UNIX timestamp) */
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private $lastKeyWrites = [];
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/** @var int Max expected delay (in seconds) for writes to reach replicas */
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const MAX_WRITE_DELAY = 5;
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/**
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* Constructor. Parameters are:
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* - writeFactory: ObjectFactory::getObjectFromSpec array yielding BagOStuff.
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* This object will be used for writes (e.g. the master DB).
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* - readFactory: ObjectFactory::getObjectFromSpec array yielding BagOStuff.
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* This object will be used for reads (e.g. a replica DB).
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* - sessionConsistencyWindow: Seconds to read from the master source for a key
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* after writing to it. [Default: ReplicatedBagOStuff::MAX_WRITE_DELAY]
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*
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* @param array $params
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* @throws InvalidArgumentException
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*/
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public function __construct( $params ) {
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parent::__construct( $params );
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if ( !isset( $params['writeFactory'] ) ) {
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throw new InvalidArgumentException(
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__METHOD__ . ': the "writeFactory" parameter is required' );
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} elseif ( !isset( $params['readFactory'] ) ) {
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throw new InvalidArgumentException(
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__METHOD__ . ': the "readFactory" parameter is required' );
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}
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$this->consistencyWindow = $params['sessionConsistencyWindow'] ?? self::MAX_WRITE_DELAY;
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$this->writeStore = ( $params['writeFactory'] instanceof BagOStuff )
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? $params['writeFactory']
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: ObjectFactory::getObjectFromSpec( $params['writeFactory'] );
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$this->readStore = ( $params['readFactory'] instanceof BagOStuff )
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? $params['readFactory']
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: ObjectFactory::getObjectFromSpec( $params['readFactory'] );
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$this->attrMap = $this->mergeFlagMaps( [ $this->readStore, $this->writeStore ] );
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}
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public function setDebug( $enabled ) {
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parent::setDebug( $enabled );
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$this->writeStore->setDebug( $enabled );
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$this->readStore->setDebug( $enabled );
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}
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public function get( $key, $flags = 0 ) {
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return (
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$this->hadRecentSessionWrite( [ $key ] ) ||
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$this->fieldHasFlags( $flags, self::READ_LATEST )
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)
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? $this->writeStore->get( $key, $flags )
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: $this->readStore->get( $key, $flags );
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}
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public function set( $key, $value, $exptime = 0, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->set( $key, $value, $exptime, $flags );
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}
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public function delete( $key, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->delete( $key, $flags );
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}
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public function add( $key, $value, $exptime = 0, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->add( $key, $value, $exptime, $flags );
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}
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public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->merge( $key, $callback, $exptime, $attempts, $flags );
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}
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public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->changeTTL( $key, $exptime, $flags );
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}
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public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
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return $this->writeStore->lock( $key, $timeout, $expiry, $rclass );
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}
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public function unlock( $key ) {
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return $this->writeStore->unlock( $key );
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}
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public function deleteObjectsExpiringBefore(
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$timestamp,
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callable $progress = null,
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$limit = INF
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) {
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return $this->writeStore->deleteObjectsExpiringBefore( $timestamp, $progress, $limit );
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}
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public function getMulti( array $keys, $flags = 0 ) {
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return (
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$this->hadRecentSessionWrite( $keys ) ||
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$this->fieldHasFlags( $flags, self::READ_LATEST )
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)
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? $this->writeStore->getMulti( $keys, $flags )
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: $this->readStore->getMulti( $keys, $flags );
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}
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public function setMulti( array $data, $exptime = 0, $flags = 0 ) {
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$this->remarkRecentSessionWrite( array_keys( $data ) );
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return $this->writeStore->setMulti( $data, $exptime, $flags );
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}
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public function deleteMulti( array $keys, $flags = 0 ) {
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$this->remarkRecentSessionWrite( $keys );
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return $this->writeStore->deleteMulti( $keys, $flags );
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}
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public function changeTTLMulti( array $keys, $exptime, $flags = 0 ) {
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$this->remarkRecentSessionWrite( $keys );
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return $this->writeStore->changeTTLMulti( $keys, $exptime, $flags );
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}
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public function incr( $key, $value = 1, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->incr( $key, $value, $flags );
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}
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public function decr( $key, $value = 1, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->decr( $key, $value, $flags );
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}
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public function incrWithInit( $key, $exptime, $value = 1, $init = null, $flags = 0 ) {
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$this->remarkRecentSessionWrite( [ $key ] );
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return $this->writeStore->incrWithInit( $key, $exptime, $value, $init, $flags );
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}
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public function getLastError() {
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return ( $this->writeStore->getLastError() !== self::ERR_NONE )
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? $this->writeStore->getLastError()
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: $this->readStore->getLastError();
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}
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public function clearLastError() {
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$this->writeStore->clearLastError();
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$this->readStore->clearLastError();
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}
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public function makeKeyInternal( $keyspace, $args ) {
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return $this->writeStore->makeKeyInternal( ...func_get_args() );
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}
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public function makeKey( $class, ...$components ) {
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return $this->writeStore->makeKey( ...func_get_args() );
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}
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public function makeGlobalKey( $class, ...$components ) {
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return $this->writeStore->makeGlobalKey( ...func_get_args() );
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}
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public function addBusyCallback( callable $workCallback ) {
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$this->writeStore->addBusyCallback( $workCallback );
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}
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public function setNewPreparedValues( array $valuesByKey ) {
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return $this->writeStore->setNewPreparedValues( $valuesByKey );
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}
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public function setMockTime( &$time ) {
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parent::setMockTime( $time );
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$this->writeStore->setMockTime( $time );
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$this->readStore->setMockTime( $time );
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}
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/**
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* @param string[] $keys
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* @return bool
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*/
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private function hadRecentSessionWrite( array $keys ) {
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$now = $this->getCurrentTime();
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foreach ( $keys as $key ) {
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$ts = $this->lastKeyWrites[$key] ?? 0;
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if ( $ts && ( $now - $ts ) <= $this->consistencyWindow ) {
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return true;
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}
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}
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return false;
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}
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/**
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* @param string[] $keys
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*/
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private function remarkRecentSessionWrite( array $keys ) {
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$now = $this->getCurrentTime();
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foreach ( $keys as $key ) {
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unset( $this->lastKeyWrites[$key] ); // move to the end
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$this->lastKeyWrites[$key] = $now;
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}
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// Prune out the map if the first key is obsolete
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if ( ( $now - reset( $this->lastKeyWrites ) ) > $this->consistencyWindow ) {
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$this->lastKeyWrites = array_filter(
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$this->lastKeyWrites,
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function ( $timestamp ) use ( $now ) {
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return ( ( $now - $timestamp ) <= $this->consistencyWindow );
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}
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);
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}
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}
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}
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