3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
16 * http://www.gnu.org/copyleft/gpl.html
19 * @author Aaron Schulz
23 * Version of PoolCounter that uses Redis
25 * There are four main redis keys used to track each pool counter key:
26 * - poolcounter:l-slots-* : A list of available slot IDs for a pool.
27 * - poolcounter:z-renewtime-* : A sorted set of (slot ID, UNIX timestamp as score)
28 * used for tracking the next time a slot should be
29 * released. This is -1 when a slot is created, and is
30 * set when released (expired), locked, and unlocked.
31 * - poolcounter:z-wait-* : A sorted set of (slot ID, UNIX timestamp as score)
32 * used for tracking waiting processes (and wait time).
33 * - poolcounter:l-wakeup-* : A list pushed to for the sake of waking up processes
34 * when a any process in the pool finishes (lasts for 1ms).
35 * For a given pool key, all the redis keys start off non-existing and are deleted if not
36 * used for a while to prevent garbage from building up on the server. They are atomically
37 * re-initialized as needed. The "z-renewtime" key is used for detecting sessions which got
38 * slots but then disappeared. Stale entries from there have their timestamp updated and the
39 * corresponding slots freed up. The "z-wait" key is used for detecting processes registered
40 * as waiting but that disappeared. Stale entries from there are deleted and the corresponding
41 * slots are freed up. The worker count is included in all the redis key names as it does not
42 * vary within each $wgPoolCounterConf type and doing so handles configuration changes.
44 * This class requires Redis 2.6 as it makes use Lua scripts for fast atomic operations.
45 * Also this should be on a server plenty of RAM for the working set to avoid evictions.
46 * Evictions could temporarily allow wait queues to double in size or temporarily cause
47 * pools to appear as full when they are not. Using volatile-ttl and bumping memory-samples
48 * in redis.conf can be helpful otherwise.
53 class PoolCounterRedis
extends PoolCounter
{
56 /** @var RedisConnectionPool */
58 /** @var array (server label => host) map */
59 protected $serversByLabel;
60 /** @var string SHA-1 of the key */
62 /** @var int TTL for locks to expire (work should finish in this time) */
65 /** @var RedisConnRef */
67 /** @var string Pool slot value */
69 /** @var int AWAKE_* constant */
71 /** @var string Unique string to identify this process */
73 /** @var int UNIX timestamp */
76 const AWAKE_ONE
= 1; // wake-up if when a slot can be taken from an existing process
77 const AWAKE_ALL
= 2; // wake-up if an existing process finishes and wake up such others
79 /** @var PoolCounterRedis[] List of active PoolCounterRedis objects in this script */
80 protected static $active = null;
82 function __construct( $conf, $type, $key ) {
83 parent
::__construct( $conf, $type, $key );
85 $this->serversByLabel
= $conf['servers'];
86 $this->ring
= new HashRing( array_fill_keys( array_keys( $conf['servers'] ), 100 ) );
88 $conf['redisConfig']['serializer'] = 'none'; // for use with Lua
89 $this->pool
= RedisConnectionPool
::singleton( $conf['redisConfig'] );
91 $this->keySha1
= sha1( $this->key
);
92 $met = ini_get( 'max_execution_time' ); // usually 0 in CLI mode
93 $this->lockTTL
= $met ?
2 * $met : 3600;
95 if ( self
::$active === null ) {
97 register_shutdown_function( [ __CLASS__
, 'releaseAll' ] );
102 * @return Status Uses RediConnRef as value on success
104 protected function getConnection() {
105 if ( !isset( $this->conn
) ) {
107 $servers = $this->ring
->getLocations( $this->key
, 3 );
108 ArrayUtils
::consistentHashSort( $servers, $this->key
);
109 foreach ( $servers as $server ) {
110 $conn = $this->pool
->getConnection( $this->serversByLabel
[$server] );
116 return Status
::newFatal( 'pool-servererror', implode( ', ', $servers ) );
120 return Status
::newGood( $this->conn
);
123 function acquireForMe() {
124 $status = $this->precheckAcquire();
125 if ( !$status->isGood() ) {
129 return $this->waitForSlotOrNotif( self
::AWAKE_ONE
);
132 function acquireForAnyone() {
133 $status = $this->precheckAcquire();
134 if ( !$status->isGood() ) {
138 return $this->waitForSlotOrNotif( self
::AWAKE_ALL
);
142 if ( $this->slot
=== null ) {
143 return Status
::newGood( PoolCounter
::NOT_LOCKED
); // not locked
146 $status = $this->getConnection();
147 if ( !$status->isOK() ) {
150 $conn = $status->value
;
152 // @codingStandardsIgnoreStart Generic.Files.LineLength
155 local kSlots,kSlotsNextRelease,kWakeup,kWaiting = unpack(KEYS)
156 local rMaxWorkers,rExpiry,rSlot,rSlotTime,rAwakeAll,rTime = unpack(ARGV)
157 -- Add the slots back to the list (if rSlot is "w" then it is not a slot).
158 -- Treat the list as expired if the "next release" time sorted-set is missing.
159 if rSlot ~= 'w' and redis.call('exists',kSlotsNextRelease) == 1 then
160 if 1*redis.call('zScore',kSlotsNextRelease,rSlot) ~= (rSlotTime + rExpiry) then
161 -- Slot lock expired and was released already
162 elseif redis.call('lLen',kSlots) >= 1*rMaxWorkers then
163 -- Slots somehow got out of sync; reset the list for sanity
164 redis.call('del',kSlots,kSlotsNextRelease)
165 elseif redis.call('lLen',kSlots) == (1*rMaxWorkers - 1) and redis.call('zCard',kWaiting) == 0 then
166 -- Slot list will be made full; clear it to save space (it re-inits as needed)
167 -- since nothing is waiting on being unblocked by a push to the list
168 redis.call('del',kSlots,kSlotsNextRelease)
170 -- Add slot back to pool and update the "next release" time
171 redis.call('rPush',kSlots,rSlot)
172 redis.call('zAdd',kSlotsNextRelease,rTime + 30,rSlot)
173 -- Always keep renewing the expiry on use
174 redis.call('expireAt',kSlots,math.ceil(rTime + rExpiry))
175 redis.call('expireAt',kSlotsNextRelease,math.ceil(rTime + rExpiry))
178 -- Update an ephemeral list to wake up other clients that can
179 -- reuse any cached work from this process. Only do this if no
180 -- slots are currently free (e.g. clients could be waiting).
181 if 1*rAwakeAll == 1 then
182 local count = redis.call('zCard',kWaiting)
184 redis.call('rPush',kWakeup,'w')
186 redis.call('pexpire',kWakeup,1)
190 // @codingStandardsIgnoreEnd
193 $conn->luaEval( $script,
195 $this->getSlotListKey(),
196 $this->getSlotRTimeSetKey(),
197 $this->getWakeupListKey(),
198 $this->getWaitSetKey(),
202 $this->slotTime
, // used for CAS-style sanity check
203 ( $this->onRelease
=== self
::AWAKE_ALL
) ?
1 : 0,
206 4 # number of first argument(s) that are keys
208 } catch ( RedisException
$e ) {
209 return Status
::newFatal( 'pool-error-unknown', $e->getMessage() );
213 $this->slotTime
= null;
214 $this->onRelease
= null;
215 unset( self
::$active[$this->session
] );
219 return Status
::newGood( PoolCounter
::RELEASED
);
223 * @param int $doWakeup AWAKE_* constant
226 protected function waitForSlotOrNotif( $doWakeup ) {
227 if ( $this->slot
!== null ) {
228 return Status
::newGood( PoolCounter
::LOCK_HELD
); // already acquired
231 $status = $this->getConnection();
232 if ( !$status->isOK() ) {
235 $conn = $status->value
;
237 $now = microtime( true );
239 $slot = $this->initAndPopPoolSlotList( $conn, $now );
240 if ( ctype_digit( $slot ) ) {
241 // Pool slot acquired by this process
243 } elseif ( $slot === 'QUEUE_FULL' ) {
244 // Too many processes are waiting for pooled processes to finish
245 return Status
::newGood( PoolCounter
::QUEUE_FULL
);
246 } elseif ( $slot === 'QUEUE_WAIT' ) {
247 // This process is now registered as waiting
248 $keys = ( $doWakeup == self
::AWAKE_ALL
)
249 // Wait for an open slot or wake-up signal (preferring the later)
250 ?
[ $this->getWakeupListKey(), $this->getSlotListKey() ]
251 // Just wait for an actual pool slot
252 : [ $this->getSlotListKey() ];
254 $res = $conn->blPop( $keys, $this->timeout
);
256 $conn->zRem( $this->getWaitSetKey(), $this->session
); // no longer waiting
257 return Status
::newGood( PoolCounter
::TIMEOUT
);
260 $slot = $res[1]; // pool slot or "w" for wake-up notifications
261 $slotTime = microtime( true ); // last microtime() was a few RTTs ago
262 // Unregister this process as waiting and bump slot "next release" time
263 $this->registerAcquisitionTime( $conn, $slot, $slotTime );
265 return Status
::newFatal( 'pool-error-unknown', "Server gave slot '$slot'." );
267 } catch ( RedisException
$e ) {
268 return Status
::newFatal( 'pool-error-unknown', $e->getMessage() );
271 if ( $slot !== 'w' ) {
273 $this->slotTime
= $slotTime;
274 $this->onRelease
= $doWakeup;
275 self
::$active[$this->session
] = $this;
280 return Status
::newGood( $slot === 'w' ? PoolCounter
::DONE
: PoolCounter
::LOCKED
);
284 * @param RedisConnRef $conn
285 * @param float $now UNIX timestamp
286 * @return string|bool False on failure
288 protected function initAndPopPoolSlotList( RedisConnRef
$conn, $now ) {
291 local kSlots,kSlotsNextRelease,kSlotWaits = unpack(KEYS)
292 local rMaxWorkers,rMaxQueue,rTimeout,rExpiry,rSess,rTime = unpack(ARGV)
293 -- Initialize if the "next release" time sorted-set is empty. The slot key
294 -- itself is empty if all slots are busy or when nothing is initialized.
295 -- If the list is empty but the set is not, then it is the later case.
296 -- For sanity, if the list exists but not the set, then reset everything.
297 if redis.call('exists',kSlotsNextRelease) == 0 then
298 redis.call('del',kSlots)
299 for i = 1,1*rMaxWorkers do
300 redis.call('rPush',kSlots,i)
301 redis.call('zAdd',kSlotsNextRelease,-1,i)
303 -- Otherwise do maintenance to clean up after network partitions
305 -- Find stale slot locks and add free them (avoid duplicates for sanity)
306 local staleLocks = redis.call('zRangeByScore',kSlotsNextRelease,0,rTime)
307 for k,slot in ipairs(staleLocks) do
308 redis.call('lRem',kSlots,0,slot)
309 redis.call('rPush',kSlots,slot)
310 redis.call('zAdd',kSlotsNextRelease,rTime + 30,slot)
312 -- Find stale wait slot entries and remove them
313 redis.call('zRemRangeByScore',kSlotWaits,0,rTime - 2*rTimeout)
316 -- Try to acquire a slot if possible now
317 if redis.call('lLen',kSlots) > 0 then
318 slot = redis.call('lPop',kSlots)
319 -- Update the slot "next release" time
320 redis.call('zAdd',kSlotsNextRelease,rTime + rExpiry,slot)
321 elseif redis.call('zCard',kSlotWaits) >= 1*rMaxQueue then
325 -- Register this process as waiting
326 redis.call('zAdd',kSlotWaits,rTime,rSess)
327 redis.call('expireAt',kSlotWaits,math.ceil(rTime + 2*rTimeout))
329 -- Always keep renewing the expiry on use
330 redis.call('expireAt',kSlots,math.ceil(rTime + rExpiry))
331 redis.call('expireAt',kSlotsNextRelease,math.ceil(rTime + rExpiry))
334 return $conn->luaEval( $script,
336 $this->getSlotListKey(),
337 $this->getSlotRTimeSetKey(),
338 $this->getWaitSetKey(),
346 3 # number of first argument(s) that are keys
351 * @param RedisConnRef $conn
352 * @param string $slot
354 * @return int|bool False on failure
356 protected function registerAcquisitionTime( RedisConnRef
$conn, $slot, $now ) {
359 local kSlots,kSlotsNextRelease,kSlotWaits = unpack(KEYS)
360 local rSlot,rExpiry,rSess,rTime = unpack(ARGV)
361 -- If rSlot is 'w' then the client was told to wake up but got no slot
363 -- Update the slot "next release" time
364 redis.call('zAdd',kSlotsNextRelease,rTime + rExpiry,rSlot)
365 -- Always keep renewing the expiry on use
366 redis.call('expireAt',kSlots,math.ceil(rTime + rExpiry))
367 redis.call('expireAt',kSlotsNextRelease,math.ceil(rTime + rExpiry))
369 -- Unregister this process as waiting
370 redis.call('zRem',kSlotWaits,rSess)
373 return $conn->luaEval( $script,
375 $this->getSlotListKey(),
376 $this->getSlotRTimeSetKey(),
377 $this->getWaitSetKey(),
383 3 # number of first argument(s) that are keys
390 protected function getSlotListKey() {
391 return "poolcounter:l-slots-{$this->keySha1}-{$this->workers}";
397 protected function getSlotRTimeSetKey() {
398 return "poolcounter:z-renewtime-{$this->keySha1}-{$this->workers}";
404 protected function getWaitSetKey() {
405 return "poolcounter:z-wait-{$this->keySha1}-{$this->workers}";
411 protected function getWakeupListKey() {
412 return "poolcounter:l-wakeup-{$this->keySha1}-{$this->workers}";
416 * Try to make sure that locks get released (even with exceptions and fatals)
418 public static function releaseAll() {
419 foreach ( self
::$active as $poolCounter ) {
421 if ( $poolCounter->slot
!== null ) {
422 $poolCounter->release();
424 } catch ( Exception
$e ) {