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RedisLockManager.php
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RedisLockManager.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 Wikimedia\ObjectCache\RedisConnectionPool;
/**
* Manage locks using redis servers.
*
* This is meant for multi-wiki systems that may share files.
* All locks are non-blocking, which avoids deadlocks.
*
* All lock requests for a resource, identified by a hash string, will map to one
* bucket. Each bucket maps to one or several peer servers, each running redis.
* A majority of peers must agree for a lock to be acquired.
*
* This class requires Redis 2.6 as it makes use of Lua scripts for fast atomic operations.
*
* @ingroup LockManager
* @since 1.22
*/
class RedisLockManager extends QuorumLockManager {
/** @var array Mapping of lock types to the type actually used */
protected $lockTypeMap = [
self::LOCK_SH => self::LOCK_SH,
self::LOCK_UW => self::LOCK_SH,
self::LOCK_EX => self::LOCK_EX
];
/** @var RedisConnectionPool */
protected $redisPool;
/** @var array Map server names to hostname/IP and port numbers */
protected $lockServers = [];
/**
* Construct a new instance from configuration.
*
* @param array $config Parameters include:
* - lockServers : Associative array of server names to "<IP>:<port>" strings.
* - srvsByBucket : An array of up to 16 arrays, each containing the server names
* in a bucket. Each bucket should have an odd number of servers.
* If omitted, all servers will be in one bucket. (optional).
* - redisConfig : Configuration for RedisConnectionPool::singleton() (optional).
* @throws Exception
*/
public function __construct( array $config ) {
parent::__construct( $config );
$this->lockServers = $config['lockServers'];
if ( isset( $config['srvsByBucket'] ) ) {
// Sanitize srvsByBucket config to prevent PHP errors
$this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
$this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
} else {
$this->srvsByBucket = [ array_keys( $this->lockServers ) ];
}
$config['redisConfig']['serializer'] = 'none';
$this->redisPool = RedisConnectionPool::singleton( $config['redisConfig'] );
}
protected function getLocksOnServer( $lockSrv, array $pathsByType ) {
$status = StatusValue::newGood();
$pathList = array_merge( ...array_values( $pathsByType ) );
$server = $this->lockServers[$lockSrv];
$conn = $this->redisPool->getConnection( $server, $this->logger );
if ( !$conn ) {
foreach ( $pathList as $path ) {
$status->fatal( 'lockmanager-fail-acquirelock', $path );
}
return $status;
}
$pathsByKey = []; // (type:hash => path) map
foreach ( $pathsByType as $type => $paths ) {
$typeString = ( $type == LockManager::LOCK_SH ) ? 'SH' : 'EX';
foreach ( $paths as $path ) {
$pathsByKey[$this->recordKeyForPath( $path, $typeString )] = $path;
}
}
try {
static $script =
/** @lang Lua */
<<<LUA
local failed = {}
-- Load input params (e.g. session, ttl, time of request)
local rSession, rTTL, rMaxTTL, rTime = unpack(ARGV)
-- Check that all the locks can be acquired
for i,requestKey in ipairs(KEYS) do
local _, _, rType, resourceKey = string.find(requestKey,"(%w+):(%w+)$")
local keyIsFree = true
local currentLocks = redis.call('hKeys',resourceKey)
for i,lockKey in ipairs(currentLocks) do
-- Get the type and session of this lock
local _, _, type, session = string.find(lockKey,"(%w+):(%w+)")
-- Check any locks that are not owned by this session
if session ~= rSession then
local lockExpiry = redis.call('hGet',resourceKey,lockKey)
if 1*lockExpiry < 1*rTime then
-- Lock is stale, so just prune it out
redis.call('hDel',resourceKey,lockKey)
elseif rType == 'EX' or type == 'EX' then
keyIsFree = false
break
end
end
end
if not keyIsFree then
failed[#failed+1] = requestKey
end
end
-- If all locks could be acquired, then do so
if #failed == 0 then
for i,requestKey in ipairs(KEYS) do
local _, _, rType, resourceKey = string.find(requestKey,"(%w+):(%w+)$")
redis.call('hSet',resourceKey,rType .. ':' .. rSession,rTime + rTTL)
-- In addition to invalidation logic, be sure to garbage collect
redis.call('expire',resourceKey,rMaxTTL)
end
end
return failed
LUA;
$res = $conn->luaEval( $script,
array_merge(
array_keys( $pathsByKey ), // KEYS[0], KEYS[1],...,KEYS[N]
[
$this->session, // ARGV[1]
$this->lockTTL, // ARGV[2]
self::MAX_LOCK_TTL, // ARGV[3]
time() // ARGV[4]
]
),
count( $pathsByKey ) # number of first argument(s) that are keys
);
} catch ( RedisException $e ) {
$res = false;
$this->redisPool->handleError( $conn, $e );
}
if ( $res === false ) {
foreach ( $pathList as $path ) {
$status->fatal( 'lockmanager-fail-acquirelock', $path );
}
} elseif ( count( $res ) ) {
$status->fatal( 'lockmanager-fail-conflict' );
}
return $status;
}
protected function freeLocksOnServer( $lockSrv, array $pathsByType ) {
$status = StatusValue::newGood();
$pathList = array_merge( ...array_values( $pathsByType ) );
$server = $this->lockServers[$lockSrv];
$conn = $this->redisPool->getConnection( $server, $this->logger );
if ( !$conn ) {
foreach ( $pathList as $path ) {
$status->fatal( 'lockmanager-fail-releaselock', $path );
}
return $status;
}
$pathsByKey = []; // (type:hash => path) map
foreach ( $pathsByType as $type => $paths ) {
$typeString = ( $type == LockManager::LOCK_SH ) ? 'SH' : 'EX';
foreach ( $paths as $path ) {
$pathsByKey[$this->recordKeyForPath( $path, $typeString )] = $path;
}
}
try {
static $script =
/** @lang Lua */
<<<LUA
local failed = {}
-- Load input params (e.g. session)
local rSession = unpack(ARGV)
for i,requestKey in ipairs(KEYS) do
local _, _, rType, resourceKey = string.find(requestKey,"(%w+):(%w+)$")
local released = redis.call('hDel',resourceKey,rType .. ':' .. rSession)
if released > 0 then
-- Remove the whole structure if it is now empty
if redis.call('hLen',resourceKey) == 0 then
redis.call('del',resourceKey)
end
else
failed[#failed+1] = requestKey
end
end
return failed
LUA;
$res = $conn->luaEval( $script,
array_merge(
array_keys( $pathsByKey ), // KEYS[0], KEYS[1],...,KEYS[N]
[
$this->session, // ARGV[1]
]
),
count( $pathsByKey ) # number of first argument(s) that are keys
);
} catch ( RedisException $e ) {
$res = false;
$this->redisPool->handleError( $conn, $e );
}
if ( $res === false ) {
foreach ( $pathList as $path ) {
$status->fatal( 'lockmanager-fail-releaselock', $path );
}
} else {
foreach ( $res as $key ) {
$status->fatal( 'lockmanager-fail-releaselock', $pathsByKey[$key] );
}
}
return $status;
}
protected function releaseAllLocks() {
return StatusValue::newGood(); // not supported
}
protected function isServerUp( $lockSrv ) {
$conn = $this->redisPool->getConnection( $this->lockServers[$lockSrv], $this->logger );
return (bool)$conn;
}
/**
* @param string $path
* @param string $type One of (EX,SH)
* @return string
*/
protected function recordKeyForPath( $path, $type ) {
return implode( ':',
[ __CLASS__, 'locks', "$type:" . $this->sha1Base36Absolute( $path ) ] );
}
/**
* Make sure remaining locks get cleared
*/
public function __destruct() {
$pathsByType = [];
foreach ( $this->locksHeld as $path => $locks ) {
foreach ( $locks as $type => $count ) {
$pathsByType[$type][] = $path;
}
}
if ( $pathsByType ) {
$this->unlockByType( $pathsByType );
}
}
}

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Wed, Aug 19, 07:50 (2 w, 3 d ago)
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RedisLockManager.php (8 KB)

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