includes/libs/objectcache/BagOStuff.php

   1 <?php
   2 /**
   3  * Copyright © 2003-2004 Brion Vibber <brion@pobox.com>
   4  * https://www.mediawiki.org/
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @file
  22  * @ingroup Cache
  23  */
  24
  25 /**
  26  * @defgroup Cache Cache
  27  */
  28
  29 use Psr\Log\LoggerAwareInterface;
  30 use Psr\Log\LoggerInterface;
  31 use Psr\Log\NullLogger;
  32
  33 /**
  34  * interface is intended to be more or less compatible with
  35  * the PHP memcached client.
  36  *
  37  * backends for local hash array and SQL table included:
  38  * @code
  39  *   $bag = new HashBagOStuff();
  40  *   $bag = new SqlBagOStuff(); # connect to db first
  41  * @endcode
  42  *
  43  * @ingroup Cache
  44  */
  45 abstract class BagOStuff implements IExpiringStore, LoggerAwareInterface {
  46         /** @var array[] Lock tracking */
  47         protected $locks = [];
  48
  49         /** @var integer */
  50         protected $lastError = self::ERR_NONE;
  51
  52         /** @var string */
  53         protected $keyspace = 'local';
  54
  55         /** @var LoggerInterface */
  56         protected $logger;
  57
  58         /** @var callback|null */
  59         protected $asyncHandler;
  60
  61         /** @var bool */
  62         private $debugMode = false;
  63
  64         /** @var array */
  65         private $duplicateKeyLookups = [];
  66
  67         /** @var bool */
  68         private $reportDupes = false;
  69
  70         /** @var bool */
  71         private $dupeTrackScheduled = false;
  72
  73         /** Possible values for getLastError() */
  74         const ERR_NONE = 0; // no error
  75         const ERR_NO_RESPONSE = 1; // no response
  76         const ERR_UNREACHABLE = 2; // can't connect
  77         const ERR_UNEXPECTED = 3; // response gave some error
  78
  79         /** Bitfield constants for get()/getMulti() */
  80         const READ_LATEST = 1; // use latest data for replicated stores
  81         const READ_VERIFIED = 2; // promise that caller can tell when keys are stale
  82         /** Bitfield constants for set()/merge() */
  83         const WRITE_SYNC = 1; // synchronously write to all locations for replicated stores
  84         const WRITE_CACHE_ONLY = 2; // Only change state of the in-memory cache
  85
  86         /**
  87          * $params include:
  88          *   - logger: Psr\Log\LoggerInterface instance
  89          *   - keyspace: Default keyspace for $this->makeKey()
  90          *   - asyncHandler: Callable to use for scheduling tasks after the web request ends.
  91          *      In CLI mode, it should run the task immediately.
  92          *   - reportDupes: Whether to emit warning log messages for all keys that were
  93          *      requested more than once (requires an asyncHandler).
  94          * @param array $params
  95          */
  96         public function __construct( array $params = [] ) {
  97                 if ( isset( $params['logger'] ) ) {
  98                         $this->setLogger( $params['logger'] );
  99                 } else {
 100                         $this->setLogger( new NullLogger() );
 101                 }
 102
 103                 if ( isset( $params['keyspace'] ) ) {
 104                         $this->keyspace = $params['keyspace'];
 105                 }
 106
 107                 $this->asyncHandler = isset( $params['asyncHandler'] )
 108                         ? $params['asyncHandler']
 109                         : null;
 110
 111                 if ( !empty( $params['reportDupes'] ) && is_callable( $this->asyncHandler ) ) {
 112                         $this->reportDupes = true;
 113                 }
 114         }
 115
 116         /**
 117          * @param LoggerInterface $logger
 118          * @return null
 119          */
 120         public function setLogger( LoggerInterface $logger ) {
 121                 $this->logger = $logger;
 122         }
 123
 124         /**
 125          * @param bool $bool
 126          */
 127         public function setDebug( $bool ) {
 128                 $this->debugMode = $bool;
 129         }
 130
 131         /**
 132          * Get an item with the given key, regenerating and setting it if not found
 133          *
 134          * If the callback returns false, then nothing is stored.
 135          *
 136          * @param string $key
 137          * @param int $ttl Time-to-live (seconds)
 138          * @param callable $callback Callback that derives the new value
 139          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 140          * @return mixed The cached value if found or the result of $callback otherwise
 141          * @since 1.27
 142          */
 143         final public function getWithSetCallback( $key, $ttl, $callback, $flags = 0 ) {
 144                 $value = $this->get( $key, $flags );
 145
 146                 if ( $value === false ) {
 147                         if ( !is_callable( $callback ) ) {
 148                                 throw new InvalidArgumentException( "Invalid cache miss callback provided." );
 149                         }
 150                         $value = call_user_func( $callback );
 151                         if ( $value !== false ) {
 152                                 $this->set( $key, $value, $ttl );
 153                         }
 154                 }
 155
 156                 return $value;
 157         }
 158
 159         /**
 160          * Get an item with the given key
 161          *
 162          * If the key includes a determistic input hash (e.g. the key can only have
 163          * the correct value) or complete staleness checks are handled by the caller
 164          * (e.g. nothing relies on the TTL), then the READ_VERIFIED flag should be set.
 165          * This lets tiered backends know they can safely upgrade a cached value to
 166          * higher tiers using standard TTLs.
 167          *
 168          * @param string $key
 169          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 170          * @param integer $oldFlags [unused]
 171          * @return mixed Returns false on failure and if the item does not exist
 172          */
 173         public function get( $key, $flags = 0, $oldFlags = null ) {
 174                 // B/C for ( $key, &$casToken = null, $flags = 0 )
 175                 $flags = is_int( $oldFlags ) ? $oldFlags : $flags;
 176
 177                 $this->trackDuplicateKeys( $key );
 178
 179                 return $this->doGet( $key, $flags );
 180         }
 181
 182         /**
 183          * Track the number of times that a given key has been used.
 184          * @param string $key
 185          */
 186         private function trackDuplicateKeys( $key ) {
 187                 if ( !$this->reportDupes ) {
 188                         return;
 189                 }
 190
 191                 if ( !isset( $this->duplicateKeyLookups[$key] ) ) {
 192                         // Track that we have seen this key. This N-1 counting style allows
 193                         // easy filtering with array_filter() later.
 194                         $this->duplicateKeyLookups[$key] = 0;
 195                 } else {
 196                         $this->duplicateKeyLookups[$key] += 1;
 197
 198                         if ( $this->dupeTrackScheduled === false ) {
 199                                 $this->dupeTrackScheduled = true;
 200                                 // Schedule a callback that logs keys processed more than once by get().
 201                                 call_user_func( $this->asyncHandler, function () {
 202                                         $dups = array_filter( $this->duplicateKeyLookups );
 203                                         foreach ( $dups as $key => $count ) {
 204                                                 $this->logger->warning(
 205                                                         'Duplicate get(): "{key}" fetched {count} times',
 206                                                         // Count is N-1 of the actual lookup count
 207                                                         [ 'key' => $key, 'count' => $count + 1, ]
 208                                                 );
 209                                         }
 210                                 } );
 211                         }
 212                 }
 213         }
 214
 215         /**
 216          * @param string $key
 217          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 218          * @return mixed Returns false on failure and if the item does not exist
 219          */
 220         abstract protected function doGet( $key, $flags = 0 );
 221
 222         /**
 223          * @note: This method is only needed if merge() uses mergeViaCas()
 224          *
 225          * @param string $key
 226          * @param mixed $casToken
 227          * @param integer $flags Bitfield of BagOStuff::READ_* constants [optional]
 228          * @return mixed Returns false on failure and if the item does not exist
 229          * @throws Exception
 230          */
 231         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 232                 throw new Exception( __METHOD__ . ' not implemented.' );
 233         }
 234
 235         /**
 236          * Set an item
 237          *
 238          * @param string $key
 239          * @param mixed $value
 240          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 241          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 242          * @return bool Success
 243          */
 244         abstract public function set( $key, $value, $exptime = 0, $flags = 0 );
 245
 246         /**
 247          * Delete an item
 248          *
 249          * @param string $key
 250          * @return bool True if the item was deleted or not found, false on failure
 251          */
 252         abstract public function delete( $key );
 253
 254         /**
 255          * Merge changes into the existing cache value (possibly creating a new one).
 256          * The callback function returns the new value given the current value
 257          * (which will be false if not present), and takes the arguments:
 258          * (this BagOStuff, cache key, current value).
 259          *
 260          * @param string $key
 261          * @param callable $callback Callback method to be executed
 262          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 263          * @param int $attempts The amount of times to attempt a merge in case of failure
 264          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 265          * @return bool Success
 266          * @throws InvalidArgumentException
 267          */
 268         public function merge( $key, $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 269                 if ( !is_callable( $callback ) ) {
 270                         throw new InvalidArgumentException( "Got invalid callback." );
 271                 }
 272
 273                 return $this->mergeViaLock( $key, $callback, $exptime, $attempts, $flags );
 274         }
 275
 276         /**
 277          * @see BagOStuff::merge()
 278          *
 279          * @param string $key
 280          * @param callable $callback Callback method to be executed
 281          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 282          * @param int $attempts The amount of times to attempt a merge in case of failure
 283          * @return bool Success
 284          */
 285         protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10 ) {
 286                 do {
 287                         $this->clearLastError();
 288                         $casToken = null; // passed by reference
 289                         $currentValue = $this->getWithToken( $key, $casToken, self::READ_LATEST );
 290                         if ( $this->getLastError() ) {
 291                                 return false; // don't spam retries (retry only on races)
 292                         }
 293
 294                         // Derive the new value from the old value
 295                         $value = call_user_func( $callback, $this, $key, $currentValue );
 296
 297                         $this->clearLastError();
 298                         if ( $value === false ) {
 299                                 $success = true; // do nothing
 300                         } elseif ( $currentValue === false ) {
 301                                 // Try to create the key, failing if it gets created in the meantime
 302                                 $success = $this->add( $key, $value, $exptime );
 303                         } else {
 304                                 // Try to update the key, failing if it gets changed in the meantime
 305                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 306                         }
 307                         if ( $this->getLastError() ) {
 308                                 return false; // IO error; don't spam retries
 309                         }
 310                 } while ( !$success && --$attempts );
 311
 312                 return $success;
 313         }
 314
 315         /**
 316          * Check and set an item
 317          *
 318          * @param mixed $casToken
 319          * @param string $key
 320          * @param mixed $value
 321          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 322          * @return bool Success
 323          * @throws Exception
 324          */
 325         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 326                 throw new Exception( "CAS is not implemented in " . __CLASS__ );
 327         }
 328
 329         /**
 330          * @see BagOStuff::merge()
 331          *
 332          * @param string $key
 333          * @param callable $callback Callback method to be executed
 334          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 335          * @param int $attempts The amount of times to attempt a merge in case of failure
 336          * @param int $flags Bitfield of BagOStuff::WRITE_* constants
 337          * @return bool Success
 338          */
 339         protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 340                 if ( !$this->lock( $key, 6 ) ) {
 341                         return false;
 342                 }
 343
 344                 $this->clearLastError();
 345                 $currentValue = $this->get( $key, self::READ_LATEST );
 346                 if ( $this->getLastError() ) {
 347                         $success = false;
 348                 } else {
 349                         // Derive the new value from the old value
 350                         $value = call_user_func( $callback, $this, $key, $currentValue );
 351                         if ( $value === false ) {
 352                                 $success = true; // do nothing
 353                         } else {
 354                                 $success = $this->set( $key, $value, $exptime, $flags ); // set the new value
 355                         }
 356                 }
 357
 358                 if ( !$this->unlock( $key ) ) {
 359                         // this should never happen
 360                         trigger_error( "Could not release lock for key '$key'." );
 361                 }
 362
 363                 return $success;
 364         }
 365
 366         /**
 367          * Acquire an advisory lock on a key string
 368          *
 369          * Note that if reentry is enabled, duplicate calls ignore $expiry
 370          *
 371          * @param string $key
 372          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 373          * @param int $expiry Lock expiry [optional]; 1 day maximum
 374          * @param string $rclass Allow reentry if set and the current lock used this value
 375          * @return bool Success
 376          */
 377         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 378                 // Avoid deadlocks and allow lock reentry if specified
 379                 if ( isset( $this->locks[$key] ) ) {
 380                         if ( $rclass != '' && $this->locks[$key]['class'] === $rclass ) {
 381                                 ++$this->locks[$key]['depth'];
 382                                 return true;
 383                         } else {
 384                                 return false;
 385                         }
 386                 }
 387
 388                 $expiry = min( $expiry ?: INF, self::TTL_DAY );
 389
 390                 $this->clearLastError();
 391                 $timestamp = microtime( true ); // starting UNIX timestamp
 392                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 393                         $locked = true;
 394                 } elseif ( $this->getLastError() || $timeout <= 0 ) {
 395                         $locked = false; // network partition or non-blocking
 396                 } else {
 397                         // Estimate the RTT (us); use 1ms minimum for sanity
 398                         $uRTT = max( 1e3, ceil( 1e6 * ( microtime( true ) - $timestamp ) ) );
 399                         $sleep = 2 * $uRTT; // rough time to do get()+set()
 400
 401                         $attempts = 0; // failed attempts
 402                         do {
 403                                 if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
 404                                         // Exponentially back off after failed attempts to avoid network spam.
 405                                         // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
 406                                         $sleep *= 2;
 407                                 }
 408                                 usleep( $sleep ); // back off
 409                                 $this->clearLastError();
 410                                 $locked = $this->add( "{$key}:lock", 1, $expiry );
 411                                 if ( $this->getLastError() ) {
 412                                         $locked = false; // network partition
 413                                         break;
 414                                 }
 415                         } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
 416                 }
 417
 418                 if ( $locked ) {
 419                         $this->locks[$key] = [ 'class' => $rclass, 'depth' => 1 ];
 420                 }
 421
 422                 return $locked;
 423         }
 424
 425         /**
 426          * Release an advisory lock on a key string
 427          *
 428          * @param string $key
 429          * @return bool Success
 430          */
 431         public function unlock( $key ) {
 432                 if ( isset( $this->locks[$key] ) && --$this->locks[$key]['depth'] <= 0 ) {
 433                         unset( $this->locks[$key] );
 434
 435                         return $this->delete( "{$key}:lock" );
 436                 }
 437
 438                 return true;
 439         }
 440
 441         /**
 442          * Get a lightweight exclusive self-unlocking lock
 443          *
 444          * Note that the same lock cannot be acquired twice.
 445          *
 446          * This is useful for task de-duplication or to avoid obtrusive
 447          * (though non-corrupting) DB errors like INSERT key conflicts
 448          * or deadlocks when using LOCK IN SHARE MODE.
 449          *
 450          * @param string $key
 451          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 452          * @param int $expiry Lock expiry [optional]; 1 day maximum
 453          * @param string $rclass Allow reentry if set and the current lock used this value
 454          * @return ScopedCallback|null Returns null on failure
 455          * @since 1.26
 456          */
 457         final public function getScopedLock( $key, $timeout = 6, $expiry = 30, $rclass = '' ) {
 458                 $expiry = min( $expiry ?: INF, self::TTL_DAY );
 459
 460                 if ( !$this->lock( $key, $timeout, $expiry, $rclass ) ) {
 461                         return null;
 462                 }
 463
 464                 $lSince = microtime( true ); // lock timestamp
 465
 466                 return new ScopedCallback( function() use ( $key, $lSince, $expiry ) {
 467                         $latency = .050; // latency skew (err towards keeping lock present)
 468                         $age = ( microtime( true ) - $lSince + $latency );
 469                         if ( ( $age + $latency ) >= $expiry ) {
 470                                 $this->logger->warning( "Lock for $key held too long ($age sec)." );
 471                                 return; // expired; it's not "safe" to delete the key
 472                         }
 473                         $this->unlock( $key );
 474                 } );
 475         }
 476
 477         /**
 478          * Delete all objects expiring before a certain date.
 479          * @param string $date The reference date in MW format
 480          * @param callable|bool $progressCallback Optional, a function which will be called
 481          *     regularly during long-running operations with the percentage progress
 482          *     as the first parameter.
 483          *
 484          * @return bool Success, false if unimplemented
 485          */
 486         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 487                 // stub
 488                 return false;
 489         }
 490
 491         /**
 492          * Get an associative array containing the item for each of the keys that have items.
 493          * @param array $keys List of strings
 494          * @param integer $flags Bitfield; supports READ_LATEST [optional]
 495          * @return array
 496          */
 497         public function getMulti( array $keys, $flags = 0 ) {
 498                 $res = [];
 499                 foreach ( $keys as $key ) {
 500                         $val = $this->get( $key );
 501                         if ( $val !== false ) {
 502                                 $res[$key] = $val;
 503                         }
 504                 }
 505                 return $res;
 506         }
 507
 508         /**
 509          * Batch insertion
 510          * @param array $data $key => $value assoc array
 511          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 512          * @return bool Success
 513          * @since 1.24
 514          */
 515         public function setMulti( array $data, $exptime = 0 ) {
 516                 $res = true;
 517                 foreach ( $data as $key => $value ) {
 518                         if ( !$this->set( $key, $value, $exptime ) ) {
 519                                 $res = false;
 520                         }
 521                 }
 522                 return $res;
 523         }
 524
 525         /**
 526          * @param string $key
 527          * @param mixed $value
 528          * @param int $exptime
 529          * @return bool Success
 530          */
 531         public function add( $key, $value, $exptime = 0 ) {
 532                 if ( $this->get( $key ) === false ) {
 533                         return $this->set( $key, $value, $exptime );
 534                 }
 535                 return false; // key already set
 536         }
 537
 538         /**
 539          * Increase stored value of $key by $value while preserving its TTL
 540          * @param string $key Key to increase
 541          * @param int $value Value to add to $key (Default 1)
 542          * @return int|bool New value or false on failure
 543          */
 544         public function incr( $key, $value = 1 ) {
 545                 if ( !$this->lock( $key ) ) {
 546                         return false;
 547                 }
 548                 $n = $this->get( $key );
 549                 if ( $this->isInteger( $n ) ) { // key exists?
 550                         $n += intval( $value );
 551                         $this->set( $key, max( 0, $n ) ); // exptime?
 552                 } else {
 553                         $n = false;
 554                 }
 555                 $this->unlock( $key );
 556
 557                 return $n;
 558         }
 559
 560         /**
 561          * Decrease stored value of $key by $value while preserving its TTL
 562          * @param string $key
 563          * @param int $value
 564          * @return int|bool New value or false on failure
 565          */
 566         public function decr( $key, $value = 1 ) {
 567                 return $this->incr( $key, - $value );
 568         }
 569
 570         /**
 571          * Increase stored value of $key by $value while preserving its TTL
 572          *
 573          * This will create the key with value $init and TTL $ttl instead if not present
 574          *
 575          * @param string $key
 576          * @param int $ttl
 577          * @param int $value
 578          * @param int $init
 579          * @return int|bool New value or false on failure
 580          * @since 1.24
 581          */
 582         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 583                 $newValue = $this->incr( $key, $value );
 584                 if ( $newValue === false ) {
 585                         // No key set; initialize
 586                         $newValue = $this->add( $key, (int)$init, $ttl ) ? $init : false;
 587                 }
 588                 if ( $newValue === false ) {
 589                         // Raced out initializing; increment
 590                         $newValue = $this->incr( $key, $value );
 591                 }
 592
 593                 return $newValue;
 594         }
 595
 596         /**
 597          * Get the "last error" registered; clearLastError() should be called manually
 598          * @return int ERR_* constant for the "last error" registry
 599          * @since 1.23
 600          */
 601         public function getLastError() {
 602                 return $this->lastError;
 603         }
 604
 605         /**
 606          * Clear the "last error" registry
 607          * @since 1.23
 608          */
 609         public function clearLastError() {
 610                 $this->lastError = self::ERR_NONE;
 611         }
 612
 613         /**
 614          * Set the "last error" registry
 615          * @param int $err ERR_* constant
 616          * @since 1.23
 617          */
 618         protected function setLastError( $err ) {
 619                 $this->lastError = $err;
 620         }
 621
 622         /**
 623          * Modify a cache update operation array for EventRelayer::notify()
 624          *
 625          * This is used for relayed writes, e.g. for broadcasting a change
 626          * to multiple data-centers. If the array contains a 'val' field
 627          * then the command involves setting a key to that value. Note that
 628          * for simplicity, 'val' is always a simple scalar value. This method
 629          * is used to possibly serialize the value and add any cache-specific
 630          * key/values needed for the relayer daemon (e.g. memcached flags).
 631          *
 632          * @param array $event
 633          * @return array
 634          * @since 1.26
 635          */
 636         public function modifySimpleRelayEvent( array $event ) {
 637                 return $event;
 638         }
 639
 640         /**
 641          * @param string $text
 642          */
 643         protected function debug( $text ) {
 644                 if ( $this->debugMode ) {
 645                         $this->logger->debug( "{class} debug: $text", [
 646                                 'class' => get_class( $this ),
 647                         ] );
 648                 }
 649         }
 650
 651         /**
 652          * Convert an optionally relative time to an absolute time
 653          * @param int $exptime
 654          * @return int
 655          */
 656         protected function convertExpiry( $exptime ) {
 657                 if ( $exptime != 0 && $exptime < ( 10 * self::TTL_YEAR ) ) {
 658                         return time() + $exptime;
 659                 } else {
 660                         return $exptime;
 661                 }
 662         }
 663
 664         /**
 665          * Convert an optionally absolute expiry time to a relative time. If an
 666          * absolute time is specified which is in the past, use a short expiry time.
 667          *
 668          * @param int $exptime
 669          * @return int
 670          */
 671         protected function convertToRelative( $exptime ) {
 672                 if ( $exptime >= ( 10 * self::TTL_YEAR ) ) {
 673                         $exptime -= time();
 674                         if ( $exptime <= 0 ) {
 675                                 $exptime = 1;
 676                         }
 677                         return $exptime;
 678                 } else {
 679                         return $exptime;
 680                 }
 681         }
 682
 683         /**
 684          * Check if a value is an integer
 685          *
 686          * @param mixed $value
 687          * @return bool
 688          */
 689         protected function isInteger( $value ) {
 690                 return ( is_int( $value ) || ctype_digit( $value ) );
 691         }
 692
 693         /**
 694          * Construct a cache key.
 695          *
 696          * @since 1.27
 697          * @param string $keyspace
 698          * @param array $args
 699          * @return string
 700          */
 701         public function makeKeyInternal( $keyspace, $args ) {
 702                 $key = $keyspace;
 703                 foreach ( $args as $arg ) {
 704                         $arg = str_replace( ':', '%3A', $arg );
 705                         $key = $key . ':' . $arg;
 706                 }
 707                 return strtr( $key, ' ', '_' );
 708         }
 709
 710         /**
 711          * Make a global cache key.
 712          *
 713          * @since 1.27
 714          * @param string ... Key component (variadic)
 715          * @return string
 716          */
 717         public function makeGlobalKey() {
 718                 return $this->makeKeyInternal( 'global', func_get_args() );
 719         }
 720
 721         /**
 722          * Make a cache key, scoped to this instance's keyspace.
 723          *
 724          * @since 1.27
 725          * @param string ... Key component (variadic)
 726          * @return string
 727          */
 728         public function makeKey() {
 729                 return $this->makeKeyInternal( $this->keyspace, func_get_args() );
 730         }
 731 }