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Diffstat (limited to 'includes/poolcounter/PoolCounterRedis.php')
-rw-r--r-- | includes/poolcounter/PoolCounterRedis.php | 417 |
1 files changed, 417 insertions, 0 deletions
diff --git a/includes/poolcounter/PoolCounterRedis.php b/includes/poolcounter/PoolCounterRedis.php new file mode 100644 index 00000000..d609f614 --- /dev/null +++ b/includes/poolcounter/PoolCounterRedis.php @@ -0,0 +1,417 @@ +<?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 + * @author Aaron Schulz + */ + +/** + * Version of PoolCounter that uses Redis + * + * There are four main redis keys used to track each pool counter key: + * - poolcounter:l-slots-* : A list of available slot IDs for a pool. + * - poolcounter:z-renewtime-* : A sorted set of (slot ID, UNIX timestamp as score) + * used for tracking the next time a slot should be + * released. This is -1 when a slot is created, and is + * set when released (expired), locked, and unlocked. + * - poolcounter:z-wait-* : A sorted set of (slot ID, UNIX timestamp as score) + * used for tracking waiting processes (and wait time). + * - poolcounter:l-wakeup-* : A list pushed to for the sake of waking up processes + * when a any process in the pool finishes (lasts for 1ms). + * For a given pool key, all the redis keys start off non-existing and are deleted if not + * used for a while to prevent garbage from building up on the server. They are atomically + * re-initialized as needed. The "z-renewtime" key is used for detecting sessions which got + * slots but then disappeared. Stale entries from there have their timestamp updated and the + * corresponding slots freed up. The "z-wait" key is used for detecting processes registered + * as waiting but that disappeared. Stale entries from there are deleted and the corresponding + * slots are freed up. The worker count is included in all the redis key names as it does not + * vary within each $wgPoolCounterConf type and doing so handles configuration changes. + * + * This class requires Redis 2.6 as it makes use Lua scripts for fast atomic operations. + * Also this should be on a server plenty of RAM for the working set to avoid evictions. + * Evictions could temporarily allow wait queues to double in size or temporarily cause + * pools to appear as full when they are not. Using volatile-ttl and bumping memory-samples + * in redis.conf can be helpful otherwise. + * + * @ingroup Redis + * @since 1.23 + */ +class PoolCounterRedis extends PoolCounter { + /** @var HashRing */ + protected $ring; + /** @var RedisConnectionPool */ + protected $pool; + /** @var array (server label => host) map */ + protected $serversByLabel; + /** @var string SHA-1 of the key */ + protected $keySha1; + /** @var int TTL for locks to expire (work should finish in this time) */ + protected $lockTTL; + + /** @var RedisConnRef */ + protected $conn; + /** @var string Pool slot value */ + protected $slot; + /** @var int AWAKE_* constant */ + protected $onRelease; + /** @var string Unique string to identify this process */ + protected $session; + /** @var int UNIX timestamp */ + protected $slotTime; + + const AWAKE_ONE = 1; // wake-up if when a slot can be taken from an existing process + const AWAKE_ALL = 2; // wake-up if an existing process finishes and wake up such others + + /** @var array List of active PoolCounterRedis objects in this script */ + protected static $active = null; + + function __construct( $conf, $type, $key ) { + parent::__construct( $conf, $type, $key ); + + $this->serversByLabel = $conf['servers']; + $this->ring = new HashRing( array_fill_keys( array_keys( $conf['servers'] ), 100 ) ); + + $conf['redisConfig']['serializer'] = 'none'; // for use with Lua + $this->pool = RedisConnectionPool::singleton( $conf['redisConfig'] ); + + $this->keySha1 = sha1( $this->key ); + $met = ini_get( 'max_execution_time' ); // usually 0 in CLI mode + $this->lockTTL = $met ? 2 * $met : 3600; + + if ( self::$active === null ) { + self::$active = array(); + register_shutdown_function( array( __CLASS__, 'releaseAll' ) ); + } + } + + /** + * @return Status Uses RediConnRef as value on success + */ + protected function getConnection() { + if ( !isset( $this->conn ) ) { + $conn = false; + $servers = $this->ring->getLocations( $this->key, 3 ); + ArrayUtils::consistentHashSort( $servers, $this->key ); + foreach ( $servers as $server ) { + $conn = $this->pool->getConnection( $this->serversByLabel[$server] ); + if ( $conn ) { + break; + } + } + if ( !$conn ) { + return Status::newFatal( 'pool-servererror', implode( ', ', $servers ) ); + } + $this->conn = $conn; + } + return Status::newGood( $this->conn ); + } + + function acquireForMe() { + $section = new ProfileSection( __METHOD__ ); + + return $this->waitForSlotOrNotif( self::AWAKE_ONE ); + } + + function acquireForAnyone() { + $section = new ProfileSection( __METHOD__ ); + + return $this->waitForSlotOrNotif( self::AWAKE_ALL ); + } + + function release() { + $section = new ProfileSection( __METHOD__ ); + + if ( $this->slot === null ) { + return Status::newGood( PoolCounter::NOT_LOCKED ); // not locked + } + + $status = $this->getConnection(); + if ( !$status->isOK() ) { + return $status; + } + $conn = $status->value; + + static $script = +<<<LUA + local kSlots,kSlotsNextRelease,kWakeup,kWaiting = unpack(KEYS) + local rMaxWorkers,rExpiry,rSlot,rSlotTime,rAwakeAll,rTime = unpack(ARGV) + -- Add the slots back to the list (if rSlot is "w" then it is not a slot). + -- Treat the list as expired if the "next release" time sorted-set is missing. + if rSlot ~= 'w' and redis.call('exists',kSlotsNextRelease) == 1 then + if 1*redis.call('zScore',kSlotsNextRelease,rSlot) ~= (rSlotTime + rExpiry) then + -- Slot lock expired and was released already + elseif redis.call('lLen',kSlots) >= 1*rMaxWorkers then + -- Slots somehow got out of sync; reset the list for sanity + redis.call('del',kSlots,kSlotsNextRelease) + elseif redis.call('lLen',kSlots) == (1*rMaxWorkers - 1) and redis.call('zCard',kWaiting) == 0 then + -- Slot list will be made full; clear it to save space (it re-inits as needed) + -- since nothing is waiting on being unblocked by a push to the list + redis.call('del',kSlots,kSlotsNextRelease) + else + -- Add slot back to pool and update the "next release" time + redis.call('rPush',kSlots,rSlot) + redis.call('zAdd',kSlotsNextRelease,rTime + 30,rSlot) + -- Always keep renewing the expiry on use + redis.call('expireAt',kSlots,math.ceil(rTime + rExpiry)) + redis.call('expireAt',kSlotsNextRelease,math.ceil(rTime + rExpiry)) + end + end + -- Update an ephemeral list to wake up other clients that can + -- reuse any cached work from this process. Only do this if no + -- slots are currently free (e.g. clients could be waiting). + if 1*rAwakeAll == 1 then + local count = redis.call('zCard',kWaiting) + for i = 1,count do + redis.call('rPush',kWakeup,'w') + end + redis.call('pexpire',kWakeup,1) + end + return 1 +LUA; + try { + $res = $conn->luaEval( $script, + array( + $this->getSlotListKey(), + $this->getSlotRTimeSetKey(), + $this->getWakeupListKey(), + $this->getWaitSetKey(), + $this->workers, + $this->lockTTL, + $this->slot, + $this->slotTime, // used for CAS-style sanity check + ( $this->onRelease === self::AWAKE_ALL ) ? 1 : 0, + microtime( true ) + ), + 4 # number of first argument(s) that are keys + ); + } catch ( RedisException $e ) { + return Status::newFatal( 'pool-error-unknown', $e->getMessage() ); + } + + $this->slot = null; + $this->slotTime = null; + $this->onRelease = null; + unset( self::$active[$this->session] ); + + return Status::newGood( PoolCounter::RELEASED ); + } + + /** + * @param int $doWakeup AWAKE_* constant + * @return Status + */ + protected function waitForSlotOrNotif( $doWakeup ) { + if ( $this->slot !== null ) { + return Status::newGood( PoolCounter::LOCK_HELD ); // already acquired + } + + $status = $this->getConnection(); + if ( !$status->isOK() ) { + return $status; + } + $conn = $status->value; + + $now = microtime( true ); + try { + $slot = $this->initAndPopPoolSlotList( $conn, $now ); + if ( ctype_digit( $slot ) ) { + // Pool slot acquired by this process + $slotTime = $now; + } elseif ( $slot === 'QUEUE_FULL' ) { + // Too many processes are waiting for pooled processes to finish + return Status::newGood( PoolCounter::QUEUE_FULL ); + } elseif ( $slot === 'QUEUE_WAIT' ) { + // This process is now registered as waiting + $keys = ( $doWakeup == self::AWAKE_ALL ) + // Wait for an open slot or wake-up signal (preferring the later) + ? array( $this->getWakeupListKey(), $this->getSlotListKey() ) + // Just wait for an actual pool slot + : array( $this->getSlotListKey() ); + + $res = $conn->blPop( $keys, $this->timeout ); + if ( $res === array() ) { + $conn->zRem( $this->getWaitSetKey(), $this->session ); // no longer waiting + return Status::newGood( PoolCounter::TIMEOUT ); + } + + $slot = $res[1]; // pool slot or "w" for wake-up notifications + $slotTime = microtime( true ); // last microtime() was a few RTTs ago + // Unregister this process as waiting and bump slot "next release" time + $this->registerAcquisitionTime( $conn, $slot, $slotTime ); + } else { + return Status::newFatal( 'pool-error-unknown', "Server gave slot '$slot'." ); + } + } catch ( RedisException $e ) { + return Status::newFatal( 'pool-error-unknown', $e->getMessage() ); + } + + if ( $slot !== 'w' ) { + $this->slot = $slot; + $this->slotTime = $slotTime; + $this->onRelease = $doWakeup; + self::$active[$this->session] = $this; + } + + return Status::newGood( $slot === 'w' ? PoolCounter::DONE : PoolCounter::LOCKED ); + } + + /** + * @param RedisConnRef $conn + * @param float $now UNIX timestamp + * @return string|bool False on failure + */ + protected function initAndPopPoolSlotList( RedisConnRef $conn, $now ) { + static $script = +<<<LUA + local kSlots,kSlotsNextRelease,kSlotWaits = unpack(KEYS) + local rMaxWorkers,rMaxQueue,rTimeout,rExpiry,rSess,rTime = unpack(ARGV) + -- Initialize if the "next release" time sorted-set is empty. The slot key + -- itself is empty if all slots are busy or when nothing is initialized. + -- If the list is empty but the set is not, then it is the later case. + -- For sanity, if the list exists but not the set, then reset everything. + if redis.call('exists',kSlotsNextRelease) == 0 then + redis.call('del',kSlots) + for i = 1,1*rMaxWorkers do + redis.call('rPush',kSlots,i) + redis.call('zAdd',kSlotsNextRelease,-1,i) + end + -- Otherwise do maintenance to clean up after network partitions + else + -- Find stale slot locks and add free them (avoid duplicates for sanity) + local staleLocks = redis.call('zRangeByScore',kSlotsNextRelease,0,rTime) + for k,slot in ipairs(staleLocks) do + redis.call('lRem',kSlots,0,slot) + redis.call('rPush',kSlots,slot) + redis.call('zAdd',kSlotsNextRelease,rTime + 30,slot) + end + -- Find stale wait slot entries and remove them + redis.call('zRemRangeByScore',kSlotWaits,0,rTime - 2*rTimeout) + end + local slot + -- Try to acquire a slot if possible now + if redis.call('lLen',kSlots) > 0 then + slot = redis.call('lPop',kSlots) + -- Update the slot "next release" time + redis.call('zAdd',kSlotsNextRelease,rTime + rExpiry,slot) + elseif redis.call('zCard',kSlotWaits) >= 1*rMaxQueue then + slot = 'QUEUE_FULL' + else + slot = 'QUEUE_WAIT' + -- Register this process as waiting + redis.call('zAdd',kSlotWaits,rTime,rSess) + redis.call('expireAt',kSlotWaits,math.ceil(rTime + 2*rTimeout)) + end + -- Always keep renewing the expiry on use + redis.call('expireAt',kSlots,math.ceil(rTime + rExpiry)) + redis.call('expireAt',kSlotsNextRelease,math.ceil(rTime + rExpiry)) + return slot +LUA; + return $conn->luaEval( $script, + array( + $this->getSlotListKey(), + $this->getSlotRTimeSetKey(), + $this->getWaitSetKey(), + $this->workers, + $this->maxqueue, + $this->timeout, + $this->lockTTL, + $this->session, + $now + ), + 3 # number of first argument(s) that are keys + ); + } + + /** + * @param RedisConnRef $conn + * @param string $slot + * @param float $now + * @return int|bool False on failure + */ + protected function registerAcquisitionTime( RedisConnRef $conn, $slot, $now ) { + static $script = +<<<LUA + local kSlots,kSlotsNextRelease,kSlotWaits = unpack(KEYS) + local rSlot,rExpiry,rSess,rTime = unpack(ARGV) + -- If rSlot is 'w' then the client was told to wake up but got no slot + if rSlot ~= 'w' then + -- Update the slot "next release" time + redis.call('zAdd',kSlotsNextRelease,rTime + rExpiry,rSlot) + -- Always keep renewing the expiry on use + redis.call('expireAt',kSlots,math.ceil(rTime + rExpiry)) + redis.call('expireAt',kSlotsNextRelease,math.ceil(rTime + rExpiry)) + end + -- Unregister this process as waiting + redis.call('zRem',kSlotWaits,rSess) + return 1 +LUA; + return $conn->luaEval( $script, + array( + $this->getSlotListKey(), + $this->getSlotRTimeSetKey(), + $this->getWaitSetKey(), + $slot, + $this->lockTTL, + $this->session, + $now + ), + 3 # number of first argument(s) that are keys + ); + } + + /** + * @return string + */ + protected function getSlotListKey() { + return "poolcounter:l-slots-{$this->keySha1}-{$this->workers}"; + } + + /** + * @return string + */ + protected function getSlotRTimeSetKey() { + return "poolcounter:z-renewtime-{$this->keySha1}-{$this->workers}"; + } + + /** + * @return string + */ + protected function getWaitSetKey() { + return "poolcounter:z-wait-{$this->keySha1}-{$this->workers}"; + } + + /** + * @return string + */ + protected function getWakeupListKey() { + return "poolcounter:l-wakeup-{$this->keySha1}-{$this->workers}"; + } + + /** + * Try to make sure that locks get released (even with exceptions and fatals) + */ + public static function releaseAll() { + foreach ( self::$active as $poolCounter ) { + try { + if ( $poolCounter->slot !== null ) { + $poolCounter->release(); + } + } catch ( Exception $e ) { + } + } + } +} |