Aaron Schulz has uploaded a new change for review.
https://gerrit.wikimedia.org/r/118955
Change subject: [WIP] Added a Redis pool counter class
......................................................................
[WIP] Added a Redis pool counter class
* This should be easier to set up for typical installs
Change-Id: Icb4a7481b944fa0818c4635e3edbe12d08af9924
---
M includes/AutoLoader.php
A includes/PoolCounterRedis.php
2 files changed, 341 insertions(+), 0 deletions(-)
git pull ssh://gerrit.wikimedia.org:29418/mediawiki/core
refs/changes/55/118955/1
diff --git a/includes/AutoLoader.php b/includes/AutoLoader.php
index a9080b2..f7a0568 100644
--- a/includes/AutoLoader.php
+++ b/includes/AutoLoader.php
@@ -157,6 +157,7 @@
'PhpHttpRequest' => 'includes/HttpFunctions.php',
'PoolCounter' => 'includes/PoolCounter.php',
'PoolCounter_Stub' => 'includes/PoolCounter.php',
+ 'PoolCounterRedis' => 'includes/PoolCounterRedis.php',
'PoolCounterWork' => 'includes/PoolCounter.php',
'PoolCounterWorkViaCallback' => 'includes/PoolCounter.php',
'PoolWorkArticleView' => 'includes/WikiPage.php',
diff --git a/includes/PoolCounterRedis.php b/includes/PoolCounterRedis.php
new file mode 100644
index 0000000..784d626
--- /dev/null
+++ b/includes/PoolCounterRedis.php
@@ -0,0 +1,340 @@
+<?php
+/**
+ * Provides of semaphore semantics for restricting the number
+ * of workers that may be concurrently performing the same task.
+ *
+ * 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 using Redis
+ *
+ * @since 1.23
+ */
+class PoolCounterRedis extends PoolCounter {
+ /** @var HashRing */
+ protected $ring;
+ /** @var RedisConnectionPool */
+ protected $pool;
+ /** @var array (server name => host) map */
+ protected $servers;
+
+ /** @var RedisConnRef */
+ protected $conn;
+
+ /** @var string Pool slot value */
+ protected $slot;
+ /** @var integer AWAKE_* constant */
+ protected $onRelease;
+ /** @var integer TTL for locks to expire */
+ protected $lockTTL;
+ /** @var string Unique string to identify this process */
+ protected $session;
+
+ const AWAKE_ONE = 1;
+ const AWAKE_ALL = 2;
+
+ function __construct( $conf, $type, $key ) {
+ parent::__construct( $conf, $type, $key );
+
+ $this->servers = $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'] );
+
+ $met = ini_get( 'max_execution_time' ); // this is 0 in CLI mode
+ $this->lockTTL = max( 5 * 60, 2 * (int)$met );
+
+ $this->session = wfRandomString( 32 );
+ }
+
+ /**
+ * @return Status
+ */
+ 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 ) {
+ $address = $this->servers[$server];
+ $conn = $this->pool->getConnection( $address );
+ if ( $conn ) {
+ break;
+ }
+ }
+ if ( !$conn ) {
+ return Status::newFatal( 'pool-errorunknown',
$server );
+ }
+ $this->conn = $conn;
+ }
+ return Status::newGood( $this->conn );
+ }
+
+ function acquireForMe() {
+ $section = new ProfileSection( __METHOD__ );
+
+ if ( $this->slot !== null ) {
+ return Status::newGood( PoolCounter::LOCK_HELD ); //
already acquired
+ }
+
+ $status = $this->getConnection();
+ if ( !$status->isOK() ) {
+ return $status;
+ }
+
+ return $this->waitForSlotOrNotif( $status->value, true );
+ }
+
+ function acquireForAnyone() {
+ $section = new ProfileSection( __METHOD__ );
+
+ if ( $this->slot !== null ) {
+ return Status::newGood( PoolCounter::LOCK_HELD ); //
already acquired
+ }
+
+ $status = $this->getConnection();
+ if ( !$status->isOK() ) {
+ return $status;
+ }
+
+ return $this->waitForSlotOrNotif( $status->value, true );
+ }
+
+ function release() {
+ $section = new ProfileSection( __METHOD__ );
+
+ if ( !$this->slot ) {
+ return Status::newGood( PoolCounter::NOT_LOCKED ); //
not locked
+ }
+
+ $status = $this->getConnection();
+ if ( !$status->isOK() ) {
+ return $status;
+ }
+ $conn = $status->value;
+
+ static $script =
+<<<LUA
+ local kSlots,kSlotsLastFree,kWakeup,kWaiting = unpack(KEYS)
+ local rMaxWorkers, rExpiry, rSlot, rAwakeAll, rTime =
unpack(ARGV)
+ -- If rSlot is 'w', then the client was told to wake up but
+ -- did not get an actual slot. Only add slots back to the list
+ -- if an actual slot was acquired by the client. Treat the list
+ -- as expired if the "last free" time hash is missing.
+ if rSlot ~= 'w' and redis.call('exists',kSlotsLastFree) == 1
then
+ if redis.call('lLen',kSlots) >= (1*rMaxWorkers - 1) then
+ -- Clear list to save space; it will re-init as
needed.
+ redis.call('del',kSlots,kSlotsLastFree)
+ elseif redis.call('lLen',kSlots) < 1*rMaxWorkers then
+ -- Add slot back to pool and update the "last
free" time
+ redis.call('rPush',kSlots,rSlot)
+ redis.call('zAdd',kSlotsLastFree,rTime,i)
+ -- Always keep renewing the expiry on use
+ redis.call('expire',kSlots,rExpiry)
+ redis.call('expire',kSlotsLastFree,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->getSlotFTimeSetKey(),
+ $this->getWakeupListKey(),
+ $this->getWaitSetKey(),
+ $this->workers,
+ $this->lockTTL, // how long a job
should take to finish
+ $this->slot,
+ ( $this->onRelease === self::AWAKE_ALL
) ? 1 : 0,
+ time()
+ ),
+ 4 # number of first argument(s) that are keys
+ );
+ } catch ( RedisException $e ) {
+ return Status::newFatal( 'pool-error-unknown',
$e->getMessage() );
+ }
+
+ $this->slot = null;
+ $this->onRelease = null;
+
+ return Status::newGood( PoolCounter::RELEASED );
+ }
+
+ /**
+ * @param RedisConnRef $conn
+ * @param bool $doWakeup Wake-up if an existing process finishes and
wake up such others
+ * @return Status
+ */
+ protected function waitForSlotOrNotif( RedisConnRef $conn, $doWakeup ) {
+ try {
+ $slot = $this->initAndPopPoolSlotList( $conn );
+ if ( ctype_digit( $slot ) ) {
+ // Pool slot acquired by this process
+ } elseif ( $slot === 'QUEUE_FULL' ) {
+ return Status::newGood( PoolCounter::QUEUE_FULL
);
+ } elseif ( $slot === 'QUEUE_WAIT' ) {
+ // This process is now registed as waiting
+ if ( $doWakeup ) {
+ // The order of the keys to blPop()
matters; the wale-up takes priority.
+ // When a process relents and we get a
'w' slot (from $wakeKey), then we
+ // know that the work that process did
can be reused by the caller.
+ $keys = array(
$this->getWakeupListKey(), $this->getSlotListKey() );
+ } else {
+ $keys = array( $this->getSlotListKey()
);
+ }
+ $res = $conn->blPop( $keys, $this->timeout );
// (list key,value) or ()
+ if ( $res === array() ) {
+ return Status::newGood(
PoolCounter::TIMEOUT );
+ }
+ $slot = $res[1];
+ // Unregister this process as waiting
+ $conn->sRem( $this->getWaitSetKey(),
$this->session );
+ } else {
+ return Status::newFatal( 'pool-error-unknown',
"Server gave '$slot'." );
+ }
+ } catch ( RedisException $e ) {
+ return Status::newFatal( 'pool-error-unknown',
$e->getMessage() );
+ }
+
+ $this->slot = $slot;
+ $this->onRelease = $doWakeup ? self::AWAKE_ALL :
self::AWAKE_ONE;
+
+ if ( $slot === 'w' ) {
+ // Got a "process done" notification instead of a pool
slot (only for $doWakeup)
+ return Status::newGood( PoolCounter::DONE );
+ } else {
+ return Status::newGood( PoolCounter::LOCKED );
+ }
+ }
+
+ /**
+ * @param RedisConnRef $conn
+ * @return int|string
+ */
+ protected function initAndPopPoolSlotList( RedisConnRef $conn ) {
+ static $script =
+<<<LUA
+ local kSlots,kSlotsLastFree,kSlotWaits = unpack(KEYS)
+ local rMaxWorkers,rMaxQueue,rTimeout,rExpiry,rSess,rTime =
unpack(ARGV)
+ -- Initialize if *both* the slot list and the last-free time
hash are empty.
+ -- The former happens if all slots are busy and also when
nothing is initialized.
+ -- If the list is empty but the hash is not, then it is the
later case.
+ if redis.call('exists',kSlots) == 0 and
redis.call('exists',kSlotsLastFree) == 0 then
+ for i = 1,1*rMaxWorkers do
+ redis.call('rPush',kSlots,i)
+ redis.call('zAdd',kSlotsLastFree,rTime,i)
+ end
+ -- Otherwise do maintenance to clean up after network partitions
+ else
+ -- Find stale slot locks and add free them as needed
+ local staleLocks =
redis.call('zRangeByScore',kSlotsLastFree,0,1*rTime - 1*rExpiry)
+ for k,slot in ipairs(staleLocks) do
+ redis.call('rPush',kSlots,slot)
+ redis.call('zAdd',kSlotsLastFree,rTime,slot)
+ end
+ -- Find stale wait slot entries and remove them
+ redis.call('zRemRangeByScore',kSlotWaits,0,1*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)
+ elseif redis.call('zCard',kSlotWaits) >= 1*rMaxQueue then
+ slot = 'QUEUE_FULL'
+ else
+ slot = 'QUEUE_WAIT'
+ redis.call('zAdd',kSlotWaits,rTime,rSess)
+ end
+ -- Always keep renewing the expiry on use
+ redis.call('expire',kSlots,rExpiry)
+ redis.call('expire',kSlotsLastFree,rExpiry)
+ return slot
+LUA;
+ return $conn->luaEval( $script,
+ array(
+ $this->getSlotListKey(),
+ $this->getSlotFTimeSetKey(),
+ $this->getWaitSetKey(),
+ $this->workers,
+ $this->maxqueue,
+ $this->timeout,
+ $this->lockTTL, // how long a job should take
to finish
+ $this->session,
+ time()
+ ),
+ 3 # number of first argument(s) that are keys
+ );
+ }
+
+ /**
+ * @return string
+ */
+ protected function getSlotListKey() {
+ // @note: worker count does not vary within each
$wgPoolCounterConf type
+ return 'poolcounter:l-slots-' . sha1( $this->key ) .
"-{$this->workers}";
+ }
+
+ /**
+ * @return string
+ */
+ protected function getSlotFTimeSetKey() {
+ // @note: worker count does not vary within each
$wgPoolCounterConf type
+ return 'poolcounter:z-slots-' . sha1( $this->key ) .
"-{$this->workers}";
+ }
+
+ /**
+ * @return string
+ */
+ protected function getWaitSetKey() {
+ // @note: worker count does not vary within each
$wgPoolCounterConf type
+ return 'poolcounter:z-wait-' . sha1( $this->key ) .
"-{$this->workers}";
+ }
+
+ /**
+ * @return string
+ */
+ protected function getWakeupListKey() {
+ // @note: worker count does not vary within each
$wgPoolCounterConf type
+ return 'poolcounter:l-wakeup-' . sha1( $this->key ) .
"-{$this->workers}";
+ }
+
+ /**
+ * Try to make sure that locks get released
+ */
+ function __destruct() {
+ try {
+ if ( $this->slot !== null ) {
+ $this->release();
+ }
+ } catch ( Exception $e ) {}
+ }
+}
--
To view, visit https://gerrit.wikimedia.org/r/118955
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: Icb4a7481b944fa0818c4635e3edbe12d08af9924
Gerrit-PatchSet: 1
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Aaron Schulz <asch...@wikimedia.org>
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