6a1a1698a5
Just documenting some benchmark work I did. Change-Id: Ic24edc5b857e06a8bfe83d70f2da0d7f4690c6af
419 lines
12 KiB
PHP
419 lines
12 KiB
PHP
<?php
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/**
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* Object caching using Redis (http://redis.io/).
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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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*/
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class RedisBagOStuff extends BagOStuff {
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protected $connectTimeout, $persistent, $password, $automaticFailover;
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/**
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* A list of server names, from $params['servers']
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*/
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protected $servers;
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/**
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* A cache of Redis objects, representing connections to Redis servers.
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* The key is the server name.
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*/
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protected $conns = array();
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/**
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* An array listing "dead" servers which have had a connection error in
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* the past. Servers are marked dead for a limited period of time, to
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* avoid excessive overhead from repeated connection timeouts. The key in
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* the array is the server name, the value is the UNIX timestamp at which
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* the server is resurrected.
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*/
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protected $deadServers = array();
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/**
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* Construct a RedisBagOStuff object. Parameters are:
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*
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* - servers: An array of server names. A server name may be a hostname,
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* a hostname/port combination or the absolute path of a UNIX socket.
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* If a hostname is specified but no port, the standard port number
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* 6379 will be used. Required.
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*
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* - connectTimeout: The timeout for new connections, in seconds. Optional,
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* default is 1 second.
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*
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* - persistent: Set this to true to allow connections to persist across
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* multiple web requests. False by default.
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*
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* - password: The authentication password, will be sent to Redis in
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* clear text. Optional, if it is unspecified, no AUTH command will be
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* sent.
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*
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* - automaticFailover: If this is false, then each key will be mapped to
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* a single server, and if that server is down, any requests for that key
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* will fail. If this is true, a connection failure will cause the client
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* to immediately try the next server in the list (as determined by a
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* consistent hashing algorithm). True by default. This has the
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* potential to create consistency issues if a server is slow enough to
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* flap, for example if it is in swap death.
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*/
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function __construct( $params ) {
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if ( !extension_loaded( 'redis' ) ) {
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throw new MWException( __CLASS__. ' requires the phpredis extension: ' .
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'https://github.com/nicolasff/phpredis' );
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}
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$this->servers = $params['servers'];
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$this->connectTimeout = isset( $params['connectTimeout'] )
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? $params['connectTimeout'] : 1;
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$this->persistent = !empty( $params['persistent'] );
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if ( isset( $params['password'] ) ) {
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$this->password = $params['password'];
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}
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if ( isset( $params['automaticFailover'] ) ) {
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$this->automaticFailover = $params['automaticFailover'];
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} else {
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$this->automaticFailover = true;
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}
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}
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public function get( $key ) {
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wfProfileIn( __METHOD__ );
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list( $server, $conn ) = $this->getConnection( $key );
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if ( !$conn ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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try {
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$result = $conn->get( $key );
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} catch ( RedisException $e ) {
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$result = false;
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$this->handleException( $server, $e );
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}
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$this->logRequest( 'get', $key, $server, $result );
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wfProfileOut( __METHOD__ );
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return $result;
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}
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public function set( $key, $value, $expiry = 0 ) {
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wfProfileIn( __METHOD__ );
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list( $server, $conn ) = $this->getConnection( $key );
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if ( !$conn ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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$expiry = $this->convertToRelative( $expiry );
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try {
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if ( !$expiry ) {
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// No expiry, that is very different from zero expiry in Redis
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$result = $conn->set( $key, $value );
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} else {
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$result = $conn->setex( $key, $expiry, $value );
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}
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} catch ( RedisException $e ) {
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$result = false;
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$this->handleException( $server, $e );
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}
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$this->logRequest( 'set', $key, $server, $result );
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wfProfileOut( __METHOD__ );
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return $result;
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}
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public function delete( $key, $time = 0 ) {
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wfProfileIn( __METHOD__ );
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list( $server, $conn ) = $this->getConnection( $key );
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if ( !$conn ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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try {
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$conn->delete( $key );
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// Return true even if the key didn't exist
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$result = true;
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} catch ( RedisException $e ) {
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$result = false;
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$this->handleException( $server, $e );
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}
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$this->logRequest( 'delete', $key, $server, $result );
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wfProfileOut( __METHOD__ );
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return $result;
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}
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public function getMulti( array $keys ) {
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wfProfileIn( __METHOD__ );
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$batches = array();
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$conns = array();
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foreach ( $keys as $key ) {
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list( $server, $conn ) = $this->getConnection( $key );
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if ( !$conn ) {
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continue;
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}
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$conns[$server] = $conn;
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$batches[$server][] = $key;
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}
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$result = array();
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foreach ( $batches as $server => $batchKeys ) {
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$conn = $conns[$server];
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try {
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$conn->multi( Redis::PIPELINE );
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foreach ( $batchKeys as $key ) {
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$conn->get( $key );
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}
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$batchResult = $conn->exec();
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if ( $batchResult === false ) {
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$this->debug( "multi request to $server failed" );
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continue;
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}
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foreach ( $batchResult as $i => $value ) {
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if ( $value !== false ) {
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$result[$batchKeys[$i]] = $value;
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}
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}
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} catch ( RedisException $e ) {
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$this->handleException( $server, $e );
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}
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}
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$this->debug( "getMulti for " . count( $keys ) . " keys " .
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"returned " . count( $result ) . " results" );
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wfProfileOut( __METHOD__ );
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return $result;
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}
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public function add( $key, $value, $expiry = 0 ) {
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wfProfileIn( __METHOD__ );
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list( $server, $conn ) = $this->getConnection( $key );
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if ( !$conn ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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$expiry = $this->convertToRelative( $expiry );
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try {
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$result = $conn->setnx( $key, $value );
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if ( $result && $expiry ) {
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$conn->expire( $key, $expiry );
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}
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} catch ( RedisException $e ) {
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$result = false;
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$this->handleException( $server, $e );
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}
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$this->logRequest( 'add', $key, $server, $result );
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wfProfileOut( __METHOD__ );
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return $result;
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}
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/**
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* Non-atomic implementation of replace(). Could perhaps be done atomically
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* with WATCH or scripting, but this function is rarely used.
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*/
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public function replace( $key, $value, $expiry = 0 ) {
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wfProfileIn( __METHOD__ );
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list( $server, $conn ) = $this->getConnection( $key );
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if ( !$conn ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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if ( !$conn->exists( $key ) ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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$expiry = $this->convertToRelative( $expiry );
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try {
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if ( !$expiry ) {
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$result = $conn->set( $key, $value );
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} else {
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$result = $conn->setex( $key, $expiry, $value );
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}
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} catch ( RedisException $e ) {
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$result = false;
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$this->handleException( $server, $e );
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}
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$this->logRequest( 'replace', $key, $server, $result );
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wfProfileOut( __METHOD__ );
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return $result;
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}
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/**
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* Non-atomic implementation of incr().
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*
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* Probably all callers actually want incr() to atomically initialise
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* values to zero if they don't exist, as provided by the Redis INCR
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* command. But we are constrained by the memcached-like interface to
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* return null in that case. Once the key exists, further increments are
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* atomic.
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*/
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public function incr( $key, $value = 1 ) {
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wfProfileIn( __METHOD__ );
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list( $server, $conn ) = $this->getConnection( $key );
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if ( !$conn ) {
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wfProfileOut( __METHOD__ );
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return false;
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}
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if ( !$conn->exists( $key ) ) {
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wfProfileOut( __METHOD__ );
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return null;
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}
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try {
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$result = $conn->incrBy( $key, $value );
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} catch ( RedisException $e ) {
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$result = false;
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$this->handleException( $server, $e );
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}
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$this->logRequest( 'incr', $key, $server, $result );
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wfProfileOut( __METHOD__ );
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return $result;
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}
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/**
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* Get a Redis object with a connection suitable for fetching the specified key
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*/
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protected function getConnection( $key ) {
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if ( count( $this->servers ) === 1 ) {
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$candidates = $this->servers;
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} else {
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// Use consistent hashing
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//
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// Note: Benchmarking on PHP 5.3 and 5.4 indicates that for small
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// strings, md5() is only 10% slower than hash('joaat',...) etc.,
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// since the function call overhead dominates. So there's not much
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// justification for breaking compatibility with installations
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// compiled with ./configure --disable-hash.
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$hashes = array();
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foreach ( $this->servers as $server ) {
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$hashes[$server] = md5( $server . '/' . $key );
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}
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asort( $hashes );
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if ( !$this->automaticFailover ) {
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reset( $hashes );
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$candidates = array( key( $hashes ) );
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} else {
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$candidates = array_keys( $hashes );
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}
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}
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foreach ( $candidates as $server ) {
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$conn = $this->getConnectionToServer( $server );
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if ( $conn ) {
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return array( $server, $conn );
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}
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}
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return array( false, false );
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}
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/**
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* Get a connection to the server with the specified name. Connections
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* are cached, and failures are persistent to avoid multiple timeouts.
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*
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* @return Redis object, or false on failure
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*/
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protected function getConnectionToServer( $server ) {
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if ( isset( $this->deadServers[$server] ) ) {
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$now = time();
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if ( $now > $this->deadServers[$server] ) {
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// Dead time expired
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unset( $this->deadServers[$server] );
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} else {
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// Server is dead
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$this->debug( "server $server is marked down for another " .
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($this->deadServers[$server] - $now ) .
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" seconds, can't get connection" );
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return false;
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}
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}
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if ( isset( $this->conns[$server] ) ) {
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return $this->conns[$server];
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}
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if ( substr( $server, 0, 1 ) === '/' ) {
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// UNIX domain socket
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// These are required by the redis extension to start with a slash, but
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// we still need to set the port to a special value to make it work.
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$host = $server;
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$port = 0;
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} else {
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// TCP connection
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$hostPort = IP::splitHostAndPort( $server );
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if ( !$hostPort ) {
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throw new MWException( __CLASS__.": invalid configured server \"$server\"" );
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}
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list( $host, $port ) = $hostPort;
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if ( $port === false ) {
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$port = 6379;
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}
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}
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$conn = new Redis;
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try {
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if ( $this->persistent ) {
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$this->debug( "opening persistent connection to $host:$port" );
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$result = $conn->pconnect( $host, $port, $this->connectTimeout );
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} else {
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$this->debug( "opening non-persistent connection to $host:$port" );
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$result = $conn->connect( $host, $port, $this->connectTimeout );
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}
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if ( !$result ) {
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$this->logError( "could not connect to server $server" );
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// Mark server down for 30s to avoid further timeouts
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$this->deadServers[$server] = time() + 30;
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return false;
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}
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if ( $this->password !== null ) {
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if ( !$conn->auth( $this->password ) ) {
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$this->logError( "authentication error connecting to $server" );
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}
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}
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} catch ( RedisException $e ) {
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$this->deadServers[$server] = time() + 30;
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wfDebugLog( 'redis', "Redis exception: " . $e->getMessage() . "\n" );
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return false;
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}
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$conn->setOption( Redis::OPT_SERIALIZER, Redis::SERIALIZER_PHP );
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$this->conns[$server] = $conn;
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return $conn;
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}
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/**
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* Log a fatal error
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*/
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protected function logError( $msg ) {
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wfDebugLog( 'redis', "Redis error: $msg\n" );
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}
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/**
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* The redis extension throws an exception in response to various read, write
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* and protocol errors. Sometimes it also closes the connection, sometimes
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* not. The safest response for us is to explicitly destroy the connection
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* object and let it be reopened during the next request.
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*/
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protected function handleException( $server, $e ) {
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wfDebugLog( 'redis', "Redis exception on server $server: " . $e->getMessage() . "\n" );
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unset( $this->conns[$server] );
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}
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/**
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* Send information about a single request to the debug log
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*/
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public function logRequest( $method, $key, $server, $result ) {
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$this->debug( "$method $key on $server: " .
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( $result === false ? "failure" : "success" ) );
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}
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}
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