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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
+ * @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 ) {
+ }
+ }
+ }
+}
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