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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
*/
namespace Wikimedia\ObjectCache;
use InvalidArgumentException;
use JsonSerializable;
use stdClass;
use Wikimedia\WaitConditionLoop;
/**
* Helper classs that implements most of BagOStuff for a backend.
*
* This should be used by concrete implementations only. Wrapper classes that
* proxy another BagOStuff should extend and implement BagOStuff directly.
*
* @ingroup Cache
* @since 1.34
*/
abstract class MediumSpecificBagOStuff extends BagOStuff {
/** @var array<string,array> Map of (key => (class LOCK_* constant => value) */
protected $locks = [];
/** @var int Bytes; chunk size of segmented cache values */
protected $segmentationSize;
/** @var int Bytes; maximum total size of a segmented cache value */
protected $segmentedValueMaxSize;
/** @var float Seconds; maximum expected seconds for a lock ping to reach the backend */
protected $maxLockSendDelay = 0.05;
/** @var array */
private $duplicateKeyLookups = [];
/** @var bool */
private $reportDupes = false;
/** @var bool */
private $dupeTrackScheduled = false;
/** Component to use for key construction of blob segment keys */
private const SEGMENT_COMPONENT = 'segment';
/** Idiom for doGet() to return extra information by reference */
protected const PASS_BY_REF = -1;
protected const METRIC_OP_GET = 'get';
protected const METRIC_OP_SET = 'set';
protected const METRIC_OP_DELETE = 'delete';
protected const METRIC_OP_CHANGE_TTL = 'change_ttl';
protected const METRIC_OP_ADD = 'add';
protected const METRIC_OP_INCR = 'incr';
protected const METRIC_OP_DECR = 'decr';
protected const METRIC_OP_CAS = 'cas';
protected const LOCK_RCLASS = 0;
protected const LOCK_DEPTH = 1;
protected const LOCK_TIME = 2;
protected const LOCK_EXPIRY = 3;
/**
* @see BagOStuff::__construct()
* Additional $params options include:
* - logger: Psr\Log\LoggerInterface instance
* - reportDupes: Whether to emit warning log messages for all keys that were
* requested more than once (requires an asyncHandler).
* - segmentationSize: The chunk size, in bytes, of segmented values. The value should
* not exceed the maximum size of values in the storage backend, as configured by
* the site administrator.
* - segmentedValueMaxSize: The maximum total size, in bytes, of segmented values.
* This should be configured to a reasonable size give the site traffic and the
* amount of I/O between application and cache servers that the network can handle.
*
* @param array $params
*
* @phpcs:ignore Generic.Files.LineLength
* @phan-param array{logger?:\Psr\Log\LoggerInterface,asyncHandler?:callable,reportDupes?:bool,segmentationSize?:int|float,segmentedValueMaxSize?:int} $params
*/
public function __construct( array $params = [] ) {
parent::__construct( $params );
if ( !empty( $params['reportDupes'] ) && $this->asyncHandler ) {
$this->reportDupes = true;
}
// Default to 8MiB if segmentationSize is not set
$this->segmentationSize = $params['segmentationSize'] ?? 8_388_608;
// Default to 64MiB if segmentedValueMaxSize is not set
$this->segmentedValueMaxSize = $params['segmentedValueMaxSize'] ?? 67_108_864;
}
/**
* Get an item with the given key
*
* If the key includes a deterministic input hash (e.g. the key can only have
* the correct value) or complete staleness checks are handled by the caller
* (e.g. nothing relies on the TTL), then the READ_VERIFIED flag should be set.
* This lets tiered backends know they can safely upgrade a cached value to
* higher tiers using standard TTLs.
*
* @param string $key
* @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
*
* @return mixed Returns false on failure or if the item does not exist
*/
public function get( $key, $flags = 0 ) {
$this->trackDuplicateKeys( $key );
return $this->resolveSegments( $key, $this->doGet( $key, $flags ) );
}
/**
* Track the number of times that a given key has been used.
*
* @param string $key
*/
private function trackDuplicateKeys( $key ) {
if ( !$this->reportDupes ) {
return;
}
if ( !isset( $this->duplicateKeyLookups[$key] ) ) {
// Track that we have seen this key. This N-1 counting style allows
// easy filtering with array_filter() later.
$this->duplicateKeyLookups[$key] = 0;
} else {
$this->duplicateKeyLookups[$key]++;
if ( $this->dupeTrackScheduled === false ) {
$this->dupeTrackScheduled = true;
// Schedule a callback that logs keys processed more than once by get().
( $this->asyncHandler )( function () {
$dups = array_filter( $this->duplicateKeyLookups );
foreach ( $dups as $key => $count ) {
$this->logger->warning(
'Duplicate get(): "{key}" fetched {count} times',
// Count is N-1 of the actual lookup count
[ 'key' => $key, 'count' => $count + 1, ]
);
}
} );
}
}
}
/**
* Get an item
*
* The CAS token should be null if the key does not exist or the value is corrupt
*
* @param string $key
* @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
* @param mixed &$casToken CAS token if MediumSpecificBagOStuff::PASS_BY_REF [returned]
*
* @return mixed Returns false on failure or if the item does not exist
*/
abstract protected function doGet( $key, $flags = 0, &$casToken = null );
public function set( $key, $value, $exptime = 0, $flags = 0 ) {
$entry = $this->makeValueOrSegmentList( $key, $value, $exptime, $flags, $ok );
// Only when all segments (if any) are stored should the main key be changed
return $ok && $this->doSet( $key, $entry, $exptime, $flags );
}
/**
* Set an item
*
* @param string $key
* @param mixed $value
* @param int $exptime Either an interval in seconds or a unix timestamp for expiry
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
*/
abstract protected function doSet( $key, $value, $exptime = 0, $flags = 0 );
public function delete( $key, $flags = 0 ) {
if ( !$this->fieldHasFlags( $flags, self::WRITE_ALLOW_SEGMENTS ) ) {
return $this->doDelete( $key, $flags );
}
$mainValue = $this->doGet( $key, self::READ_LATEST );
if ( !$this->doDelete( $key, $flags ) ) {
return false;
}
if ( !SerializedValueContainer::isSegmented( $mainValue ) ) {
// no segments to delete
return true;
}
$orderedKeys = array_map(
function ( $segmentHash ) use ( $key ) {
return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
},
$mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
);
return $this->deleteMulti( $orderedKeys, $flags & ~self::WRITE_ALLOW_SEGMENTS );
}
/**
* Delete an item
*
* @param string $key
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool True if the item was deleted or not found, false on failure
*/
abstract protected function doDelete( $key, $flags = 0 );
public function add( $key, $value, $exptime = 0, $flags = 0 ) {
$entry = $this->makeValueOrSegmentList( $key, $value, $exptime, $flags, $ok );
// Only when all segments (if any) are stored should the main key be changed
return $ok && $this->doAdd( $key, $entry, $exptime, $flags );
}
/**
* Insert an item if it does not already exist
*
* @param string $key
* @param mixed $value
* @param int $exptime
* @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
*
* @return bool Success
*/
abstract protected function doAdd( $key, $value, $exptime = 0, $flags = 0 );
/**
* Merge changes into the existing cache value (possibly creating a new one)
*
* The callback function returns the new value given the current value
* (which will be false if not present), and takes the arguments:
* (this BagOStuff, cache key, current value, TTL).
* The TTL parameter is reference set to $exptime. It can be overridden in the callback.
* Nothing is stored nor deleted if the callback returns false.
*
* @param string $key
* @param callable $callback Callback method to be executed
* @param int $exptime Either an interval in seconds or a unix timestamp for expiry
* @param int $attempts The amount of times to attempt a merge in case of failure
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
*/
public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
return $this->mergeViaCas( $key, $callback, $exptime, $attempts, $flags );
}
/**
* @param string $key
* @param callable $callback Callback method to be executed
* @param int $exptime Either an interval in seconds or a unix timestamp for expiry
* @param int $attempts The amount of times to attempt a merge in case of failure
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
* @see BagOStuff::merge()
*/
final protected function mergeViaCas( $key, callable $callback, $exptime, $attempts, $flags ) {
$attemptsLeft = $attempts;
do {
$token = self::PASS_BY_REF;
// Get the old value and CAS token from cache
$watchPoint = $this->watchErrors();
$currentValue = $this->resolveSegments(
$key,
$this->doGet( $key, $flags, $token )
);
if ( $this->getLastError( $watchPoint ) ) {
// Don't spam slow retries due to network problems (retry only on races)
$this->logger->warning(
__METHOD__ . ' failed due to read I/O error on get() for {key}.', [ 'key' => $key ]
);
$success = false;
break;
}
// Derive the new value from the old value
$value = $callback( $this, $key, $currentValue, $exptime );
$keyWasNonexistent = ( $currentValue === false );
$valueMatchesOldValue = ( $value === $currentValue );
// free RAM in case the value is large
unset( $currentValue );
$watchPoint = $this->watchErrors();
if ( $value === false || $exptime < 0 ) {
// do nothing
$success = true;
} elseif ( $valueMatchesOldValue && $attemptsLeft !== $attempts ) {
// recently set by another thread to the same value
$success = true;
} elseif ( $keyWasNonexistent ) {
// Try to create the key, failing if it gets created in the meantime
$success = $this->add( $key, $value, $exptime, $flags );
} else {
// Try to update the key, failing if it gets changed in the meantime
$success = $this->cas( $token, $key, $value, $exptime, $flags );
}
if ( $this->getLastError( $watchPoint ) ) {
// Don't spam slow retries due to network problems (retry only on races)
$this->logger->warning(
__METHOD__ . ' failed due to write I/O error for {key}.',
[ 'key' => $key ]
);
$success = false;
break;
}
} while ( !$success && --$attemptsLeft );
return $success;
}
/**
* Set an item if the current CAS token matches the provided CAS token
*
* @param mixed $casToken Only set the item if it still has this CAS token
* @param string $key
* @param mixed $value
* @param int $exptime Either an interval in seconds or a unix timestamp for expiry
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
*/
protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
if ( $casToken === null ) {
$this->logger->warning(
__METHOD__ . ' got empty CAS token for {key}.',
[ 'key' => $key ]
);
// caller may have meant to use add()?
return false;
}
$entry = $this->makeValueOrSegmentList( $key, $value, $exptime, $flags, $ok );
// Only when all segments (if any) are stored should the main key be changed
return $ok && $this->doCas( $casToken, $key, $entry, $exptime, $flags );
}
/**
* Set an item if the current CAS token matches the provided CAS token
*
* @param mixed $casToken CAS token from an existing version of the key
* @param string $key
* @param mixed $value
* @param int $exptime Either an interval in seconds or a unix timestamp for expiry
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
*/
protected function doCas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
// @TODO: the use of lock() assumes that all other relevant sets() use a lock
if ( !$this->lock( $key, 0 ) ) {
// non-blocking
return false;
}
$curCasToken = self::PASS_BY_REF;
$watchPoint = $this->watchErrors();
$exists = ( $this->doGet( $key, self::READ_LATEST, $curCasToken ) !== false );
if ( $this->getLastError( $watchPoint ) ) {
// Fail if the old CAS token could not be read
$success = false;
$this->logger->warning(
__METHOD__ . ' failed due to write I/O error for {key}.',
[ 'key' => $key ]
);
} elseif ( $exists && $this->tokensMatch( $casToken, $curCasToken ) ) {
$success = $this->doSet( $key, $value, $exptime, $flags );
} else {
// mismatched or failed
$success = false;
$this->logger->info(
__METHOD__ . ' failed due to race condition for {key}.',
[ 'key' => $key, 'key_exists' => $exists ]
);
}
$this->unlock( $key );
return $success;
}
/**
* @param mixed $value CAS token for an existing key
* @param mixed $otherValue CAS token for an existing key
*
* @return bool Whether the two tokens match
*/
final protected function tokensMatch( $value, $otherValue ) {
$type = gettype( $value );
// Ideally, tokens are counters, timestamps, hashes, or serialized PHP values.
// However, some classes might use the PHP values themselves.
if ( $type !== gettype( $otherValue ) ) {
return false;
}
// Serialize both tokens to strictly compare objects or arrays (which might objects
// nested inside). Note that this will not apply if integer/string CAS tokens are used.
if ( $type === 'array' || $type === 'object' ) {
return ( serialize( $value ) === serialize( $otherValue ) );
}
// For string/integer tokens, use a simple comparison
return ( $value === $otherValue );
}
/**
* Change the expiration on a key if it exists
*
* If an expiry in the past is given then the key will immediately be expired
*
* For large values written using WRITE_ALLOW_SEGMENTS, this only changes the TTL of the
* main segment list key. While lowering the TTL of the segment list key has the effect of
* functionally lowering the TTL of the key, it might leave unused blobs in cache for longer.
* Raising the TTL of such keys is not effective, since the expiration of a single segment
* key effectively expires the entire value.
*
* @param string $key
* @param int $exptime TTL or UNIX timestamp
* @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
*
* @return bool Success Returns false on failure or if the item does not exist
* @since 1.28
*/
public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
return $this->doChangeTTL( $key, $exptime, $flags );
}
/**
* @param string $key
* @param int $exptime
* @param int $flags
*
* @return bool
*/
protected function doChangeTTL( $key, $exptime, $flags ) {
// @TODO: the use of lock() assumes that all other relevant sets() use a lock
if ( !$this->lock( $key, 0 ) ) {
return false;
}
$expiry = $this->getExpirationAsTimestamp( $exptime );
$delete = ( $expiry != self::TTL_INDEFINITE && $expiry < $this->getCurrentTime() );
// Use doGet() to avoid having to trigger resolveSegments()
$blob = $this->doGet( $key, self::READ_LATEST );
if ( $blob ) {
if ( $delete ) {
$ok = $this->doDelete( $key, $flags );
} else {
$ok = $this->doSet( $key, $blob, $exptime, $flags );
}
} else {
$ok = false;
}
$this->unlock( $key );
return $ok;
}
public function incrWithInit( $key, $exptime, $step = 1, $init = null, $flags = 0 ) {
$step = (int)$step;
$init = is_int( $init ) ? $init : $step;
return $this->doIncrWithInit( $key, $exptime, $step, $init, $flags );
}
/**
* @param string $key
* @param int $exptime
* @param int $step
* @param int $init
* @param int $flags
*
* @return int|bool New value or false on failure
*/
abstract protected function doIncrWithInit( $key, $exptime, $step, $init, $flags );
/**
* @param string $key
* @param int $timeout
* @param int $exptime
* @param string $rclass
*
* @return bool
*/
public function lock( $key, $timeout = 6, $exptime = 6, $rclass = '' ) {
$exptime = min( $exptime ?: INF, self::TTL_DAY );
$acquired = false;
if ( isset( $this->locks[$key] ) ) {
// Already locked; avoid deadlocks and allow lock reentry if specified
if ( $rclass != '' && $this->locks[$key][self::LOCK_RCLASS] === $rclass ) {
++$this->locks[$key][self::LOCK_DEPTH];
$acquired = true;
}
} else {
// Not already locked; acquire a lock on the backend
$lockTsUnix = $this->doLock( $key, $timeout, $exptime );
if ( $lockTsUnix !== null ) {
$this->locks[$key] = [
self::LOCK_RCLASS => $rclass,
self::LOCK_DEPTH => 1,
self::LOCK_TIME => $lockTsUnix,
self::LOCK_EXPIRY => $lockTsUnix + $exptime
];
$acquired = true;
}
}
return $acquired;
}
/**
* @see MediumSpecificBagOStuff::lock()
*
* @param string $key
* @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
* @param int $exptime Lock time-to-live 1 day maximum [optional]
*
* @return float|null UNIX timestamp of acquisition; null on failure
*/
protected function doLock( $key, $timeout, $exptime ) {
$lockTsUnix = null;
$fname = __METHOD__;
$loop = new WaitConditionLoop(
function () use ( $key, $exptime, $fname, &$lockTsUnix ) {
$watchPoint = $this->watchErrors();
if ( $this->add( $this->makeLockKey( $key ), 1, $exptime ) ) {
$lockTsUnix = microtime( true );
return WaitConditionLoop::CONDITION_REACHED;
} elseif ( $this->getLastError( $watchPoint ) ) {
$this->logger->warning(
"$fname failed due to I/O error for {key}.",
[ 'key' => $key ]
);
return WaitConditionLoop::CONDITION_ABORTED;
}
return WaitConditionLoop::CONDITION_CONTINUE;
},
$timeout
);
$code = $loop->invoke();
if ( $code === $loop::CONDITION_TIMED_OUT ) {
$this->logger->warning(
"$fname failed due to timeout for {key}.",
[ 'key' => $key, 'timeout' => $timeout ]
);
}
return $lockTsUnix;
}
/**
* Release an advisory lock on a key string
*
* @param string $key
*
* @return bool Success
*/
public function unlock( $key ) {
$released = false;
if ( isset( $this->locks[$key] ) ) {
if ( --$this->locks[$key][self::LOCK_DEPTH] > 0 ) {
$released = true;
} else {
$released = $this->doUnlock( $key );
unset( $this->locks[$key] );
if ( !$released ) {
$this->logger->warning(
__METHOD__ . ' failed to release lock for {key}.',
[ 'key' => $key ]
);
}
}
} else {
$this->logger->warning(
__METHOD__ . ' no lock to release for {key}.',
[ 'key' => $key ]
);
}
return $released;
}
/**
* @see MediumSpecificBagOStuff::unlock()
*
* @param string $key
*
* @return bool Success
*/
protected function doUnlock( $key ) {
$released = false;
// Estimate the remaining TTL of the lock key
$curTTL = $this->locks[$key][self::LOCK_EXPIRY] - $this->getCurrentTime();
// Check the risk of race conditions for key deletion
if ( $this->getQoS( self::ATTR_DURABILITY ) <= self::QOS_DURABILITY_SCRIPT ) {
// Lock (and data) keys use memory specific to this request (e.g. HashBagOStuff)
$isSafe = true;
} else {
// It is unsafe to delete the lock key if there is a serious risk of the key already
// being claimed by another thread before the delete operation reaches the backend
$isSafe = ( $curTTL > $this->maxLockSendDelay );
}
if ( $isSafe ) {
$released = $this->doDelete( $this->makeLockKey( $key ) );
} else {
$this->logger->warning(
"Lock for {key} held too long ({age} sec).",
[ 'key' => $key, 'curTTL' => $curTTL ]
);
}
return $released;
}
/**
* @param string $key
*
* @return string
*/
protected function makeLockKey( $key ) {
return "$key:lock";
}
public function deleteObjectsExpiringBefore(
$timestamp,
?callable $progress = null,
$limit = INF,
?string $tag = null
) {
return false;
}
/**
* Get an associative array containing the item for each of the keys that have items.
*
* @param string[] $keys List of keys; can be a map of (unused => key) for convenience
* @param int $flags Bitfield; supports READ_LATEST [optional]
*
* @return mixed[] Map of (key => value) for existing keys; preserves the order of $keys
*/
public function getMulti( array $keys, $flags = 0 ) {
$foundByKey = $this->doGetMulti( $keys, $flags );
$res = [];
foreach ( $keys as $key ) {
// Resolve one blob at a time (avoids too much I/O at once)
if ( array_key_exists( $key, $foundByKey ) ) {
// A value should not appear in the key if a segment is missing
$value = $this->resolveSegments( $key, $foundByKey[$key] );
if ( $value !== false ) {
$res[$key] = $value;
}
}
}
return $res;
}
/**
* Get an associative array containing the item for each of the keys that have items.
*
* @param string[] $keys List of keys
* @param int $flags Bitfield; supports READ_LATEST [optional]
*
* @return array Map of (key => value) for existing keys; preserves the order of $keys
*/
protected function doGetMulti( array $keys, $flags = 0 ) {
$res = [];
foreach ( $keys as $key ) {
$val = $this->doGet( $key, $flags );
if ( $val !== false ) {
$res[$key] = $val;
}
}
return $res;
}
/**
* Batch insertion/replace
*
* This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
*
* @param mixed[] $valueByKey Map of (key => value)
* @param int $exptime Either an interval in seconds or a unix timestamp for expiry
* @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
*
* @return bool Success
* @since 1.24
*/
public function setMulti( array $valueByKey, $exptime = 0, $flags = 0 ) {
if ( $this->fieldHasFlags( $flags, self::WRITE_ALLOW_SEGMENTS ) ) {
throw new InvalidArgumentException( __METHOD__ . ' got WRITE_ALLOW_SEGMENTS' );
}
return $this->doSetMulti( $valueByKey, $exptime, $flags );
}
/**
* @param mixed[] $data Map of (key => value)
* @param int $exptime Either an interval in seconds or a unix timestamp for expiry
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
*/
protected function doSetMulti( array $data, $exptime = 0, $flags = 0 ) {
$res = true;
foreach ( $data as $key => $value ) {
$res = $this->doSet( $key, $value, $exptime, $flags ) && $res;
}
return $res;
}
public function deleteMulti( array $keys, $flags = 0 ) {
if ( $this->fieldHasFlags( $flags, self::WRITE_ALLOW_SEGMENTS ) ) {
throw new InvalidArgumentException( __METHOD__ . ' got WRITE_ALLOW_SEGMENTS' );
}
return $this->doDeleteMulti( $keys, $flags );
}
/**
* @param string[] $keys List of keys
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
*/
protected function doDeleteMulti( array $keys, $flags = 0 ) {
$res = true;
foreach ( $keys as $key ) {
$res = $this->doDelete( $key, $flags ) && $res;
}
return $res;
}
/**
* Change the expiration of multiple keys that exist
*
* @param string[] $keys List of keys
* @param int $exptime TTL or UNIX timestamp
* @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
*
* @return bool Success
*
* @since 1.34
*/
public function changeTTLMulti( array $keys, $exptime, $flags = 0 ) {
return $this->doChangeTTLMulti( $keys, $exptime, $flags );
}
/**
* @param string[] $keys List of keys
* @param int $exptime TTL or UNIX timestamp
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*
* @return bool Success
*/
protected function doChangeTTLMulti( array $keys, $exptime, $flags = 0 ) {
$res = true;
foreach ( $keys as $key ) {
$res = $this->doChangeTTL( $key, $exptime, $flags ) && $res;
}
return $res;
}
/**
* Get and reassemble the chunks of blob at the given key
*
* @param string $key
* @param mixed $mainValue
*
* @return string|null|bool The combined string, false if missing, null on error
*/
final protected function resolveSegments( $key, $mainValue ) {
if ( SerializedValueContainer::isSegmented( $mainValue ) ) {
$orderedKeys = array_map(
function ( $segmentHash ) use ( $key ) {
return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
},
$mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
);
$segmentsByKey = $this->doGetMulti( $orderedKeys );
$parts = [];
foreach ( $orderedKeys as $segmentKey ) {
if ( isset( $segmentsByKey[$segmentKey] ) ) {
$parts[] = $segmentsByKey[$segmentKey];
} else {
// missing segment
return false;
}
}
return $this->unserialize( implode( '', $parts ) );
}
return $mainValue;
}
/**
* Check if a value should use a segmentation wrapper due to its size
*
* In order to avoid extra serialization and/or twice-serialized wrappers, just check if
* the value is a large string. Support cache wrappers (e.g. WANObjectCache) that use 2D
* arrays to wrap values. This does not recurse in order to avoid overhead from complex
* structures and the risk of infinite loops (due to references).
*
* @param mixed $value
* @param int $flags
*
* @return bool
*/
private function useSegmentationWrapper( $value, $flags ) {
if (
$this->segmentationSize === INF ||
!$this->fieldHasFlags( $flags, self::WRITE_ALLOW_SEGMENTS )
) {
return false;
}
if ( is_string( $value ) ) {
return ( strlen( $value ) >= $this->segmentationSize );
}
if ( is_array( $value ) ) {
// Expect that the contained value will be one of the first array entries
foreach ( array_slice( $value, 0, 4 ) as $v ) {
if ( is_string( $v ) && strlen( $v ) >= $this->segmentationSize ) {
return true;
}
}
}
// Avoid breaking functions for incrementing/decrementing integer key values
return false;
}
/**
* Make the entry to store at a key (inline or segment list), storing any segments
*
* @param string $key
* @param mixed $value
* @param int $exptime
* @param int $flags
* @param mixed|null &$ok Whether the entry is usable (e.g. no missing segments) [returned]
*
* @return mixed The entry (inline value, wrapped inline value, or wrapped segment list)
* @since 1.34
*/
final protected function makeValueOrSegmentList( $key, $value, $exptime, $flags, &$ok ) {
$entry = $value;
$ok = true;
if ( $this->useSegmentationWrapper( $value, $flags ) ) {
$segmentSize = $this->segmentationSize;
$maxTotalSize = $this->segmentedValueMaxSize;
$serialized = $this->getSerialized( $value, $key );
$size = strlen( $serialized );
if ( $size > $maxTotalSize ) {
$this->logger->warning(
"Value for {key} exceeds $maxTotalSize bytes; cannot segment.",
[ 'key' => $key ]
);
} else {
// Split the serialized value into chunks and store them at different keys
$chunksByKey = [];
$segmentHashes = [];
$count = intdiv( $size, $segmentSize ) + ( ( $size % $segmentSize ) ? 1 : 0 );
for ( $i = 0; $i < $count; ++$i ) {
$segment = substr( $serialized, $i * $segmentSize, $segmentSize );
$hash = sha1( $segment );
$chunkKey = $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $hash );
$chunksByKey[$chunkKey] = $segment;
$segmentHashes[] = $hash;
}
$flags &= ~self::WRITE_ALLOW_SEGMENTS;
$ok = $this->setMulti( $chunksByKey, $exptime, $flags );
$entry = SerializedValueContainer::newSegmented( $segmentHashes );
}
}
return $entry;
}
/**
* @param int|float $exptime
*
* @return bool Whether the expiry is non-infinite, and, negative or not a UNIX timestamp
* @since 1.34
*/
final protected function isRelativeExpiration( $exptime ) {
return ( $exptime !== self::TTL_INDEFINITE && $exptime < ( 10 * self::TTL_YEAR ) );
}
/**
* Convert an optionally relative timestamp to an absolute time
*
* The input value will be cast to an integer and interpreted as follows:
* - zero: no expiry; return zero (e.g. TTL_INDEFINITE)
* - negative: relative TTL; return UNIX timestamp offset by this value
* - positive (< 10 years): relative TTL; return UNIX timestamp offset by this value
* - positive (>= 10 years): absolute UNIX timestamp; return this value
*
* @param int $exptime
*
* @return int Expiration timestamp or TTL_INDEFINITE for indefinite
* @since 1.34
*/
final protected function getExpirationAsTimestamp( $exptime ) {
if ( $exptime == self::TTL_INDEFINITE ) {
return $exptime;
}
return $this->isRelativeExpiration( $exptime )
? intval( $this->getCurrentTime() + $exptime )
: $exptime;
}
/**
* Convert an optionally absolute expiry time to a relative time. If an
* absolute time is specified which is in the past, use a short expiry time.
*
* The input value will be cast to an integer and interpreted as follows:
* - zero: no expiry; return zero (e.g. TTL_INDEFINITE)
* - negative: relative TTL; return a short expiry time (1 second)
* - positive (< 10 years): relative TTL; return this value
* - positive (>= 10 years): absolute UNIX timestamp; return offset to current time
*
* @param int $exptime
*
* @return int Relative TTL or TTL_INDEFINITE for indefinite
* @since 1.34
*/
final protected function getExpirationAsTTL( $exptime ) {
if ( $exptime == self::TTL_INDEFINITE ) {
return $exptime;
}
return $this->isRelativeExpiration( $exptime )
? $exptime
: (int)max( $exptime - $this->getCurrentTime(), 1 );
}
/**
* Check if a value is an integer
*
* @param mixed $value
*
* @return bool
*/
final protected function isInteger( $value ) {
if ( is_int( $value ) ) {
return true;
} elseif ( !is_string( $value ) ) {
return false;
}
$integer = (int)$value;
return ( $value === (string)$integer );
}
public function getQoS( $flag ) {
return $this->attrMap[$flag] ?? self::QOS_UNKNOWN;
}
/**
* @deprecated since 1.43, not used anywhere.
*/
public function getSegmentationSize() {
wfDeprecated( __METHOD__, '1.43' );
return $this->segmentationSize;
}
/**
* @deprecated since 1.43, not used anywhere.
*/
public function getSegmentedValueMaxSize() {
wfDeprecated( __METHOD__, '1.43' );
return $this->segmentedValueMaxSize;
}
/**
* Get the serialized form a value, logging a warning if it involves custom classes
*
* @param mixed $value
* @param string $key
*
* @return string|int String/integer representation of value
* @since 1.35
*/
protected function getSerialized( $value, $key ) {
$this->checkValueSerializability( $value, $key );
return $this->serialize( $value );
}
/**
* Log if a new cache value does not appear suitable for serialization at a quick glance
*
* This aids migration of values to JSON-like structures and the debugging of exceptions
* due to serialization failure.
*
* This does not recurse more than one level into container structures.
*
* A proper cache key value is one of the following:
* - null
* - a scalar
* - an array with scalar/null values
* - an array tree with scalar/null "leaf" values
* - an stdClass instance with scalar/null field values
* - an stdClass instance tree with scalar/null "leaf" values
* - an instance of a class that implements JsonSerializable
*
* @param mixed $value Result of the value generation callback for the key
* @param string $key Cache key
*/
private function checkValueSerializability( $value, $key ) {
if ( is_array( $value ) ) {
$this->checkIterableMapSerializability( $value, $key );
} elseif ( is_object( $value ) ) {
// Note that Closure instances count as objects
if ( $value instanceof stdClass ) {
$this->checkIterableMapSerializability( $value, $key );
} elseif ( !( $value instanceof JsonSerializable ) ) {
$this->logger->warning(
"{class} value for '{cachekey}'; serialization is suspect.",
[ 'cachekey' => $key, 'class' => get_class( $value ) ]
);
}
}
}
/**
* @param array|stdClass $value Result of the value generation callback for the key
* @param string $key Cache key
*/
private function checkIterableMapSerializability( $value, $key ) {
foreach ( $value as $index => $entry ) {
if ( is_object( $entry ) ) {
// Note that Closure instances count as objects
if (
!( $entry instanceof \stdClass ) &&
!( $entry instanceof \JsonSerializable )
) {
$this->logger->warning(
"{class} value for '{cachekey}' at '$index'; serialization is suspect.",
[ 'cachekey' => $key, 'class' => get_class( $entry ) ]
);
return;
}
}
}
}
/**
* @param mixed $value
*
* @return string|int|false String/integer representation
* @note Special handling is usually needed for integers so incr()/decr() work
*/
protected function serialize( $value ) {
return is_int( $value ) ? $value : serialize( $value );
}
/**
* @param string|int|false $value
*
* @return mixed Original value or false on error
* @note Special handling is usually needed for integers so incr()/decr() work
*/
protected function unserialize( $value ) {
return $this->isInteger( $value ) ? (int)$value : unserialize( $value );
}
/**
* @param string $text
*/
protected function debug( $text ) {
$this->logger->debug( "{class} debug: $text", [ 'class' => static::class ] );
}
/**
* @param string $key Key generated by BagOStuff::makeKeyInternal
*
* @return string A stats prefix to describe this class of key (e.g. "objectcache.file")
*/
private function determinekeyGroupForStats( $key ): string {
// Key came directly from BagOStuff::makeKey() or BagOStuff::makeGlobalKey()
// and thus has the format of "<scope>:<collection>[:<constant or variable>]..."
$components = explode( ':', $key, 3 );
// Handle legacy callers that fail to use the key building methods
$keygroup = $components[1] ?? 'UNKNOWN';
return strtr( $keygroup, '.', '_' );
}
/**
* @param string $op Operation name as a MediumSpecificBagOStuff::METRIC_OP_* constant
* @param array<int,string>|array<string,int[]> $keyInfo Key list, if payload sizes are not
* applicable, otherwise, map of (key => (send payload size, receive payload size)); send
* and receive sizes are 0 where not applicable and receive sizes are "false" for keys
* that were not found during read operations
*/
protected function updateOpStats( string $op, array $keyInfo ) {
$deltasByMetric = [];
foreach ( $keyInfo as $indexOrKey => $keyOrSizes ) {
if ( is_array( $keyOrSizes ) ) {
$key = $indexOrKey;
[ $sPayloadSize, $rPayloadSize ] = $keyOrSizes;
} else {
$key = $keyOrSizes;
$sPayloadSize = 0;
$rPayloadSize = 0;
}
// Metric prefix for the cache wrapper and key collection name
$keygroup = $this->determinekeyGroupForStats( $key );
if ( $op === self::METRIC_OP_GET ) {
// This operation was either a "hit" or "miss" for this key
if ( $rPayloadSize === false ) {
$statsdName = "objectcache.{$keygroup}.{$op}_miss_rate";
$statsName = "bagostuff_miss_total";
} else {
$statsdName = "objectcache.{$keygroup}.{$op}_hit_rate";
$statsName = "bagostuff_hit_total";
}
} else {
// There is no concept of "hit" or "miss" for this operation
$statsdName = "objectcache.{$keygroup}.{$op}_call_rate";
$statsName = "bagostuff_call_total";
}
$deltasByMetric[$statsdName] = [
'delta' => ( $deltasByMetric[$statsdName]['delta'] ?? 0 ) + 1,
'metric' => $statsName,
'keygroup' => $keygroup,
'operation' => $op,
];
if ( $sPayloadSize > 0 ) {
$statsdName = "objectcache.{$keygroup}.{$op}_bytes_sent";
$statsName = "bagostuff_bytes_sent_total";
$deltasByMetric[$statsdName] = [
'delta' => ( $deltasByMetric[$statsdName]['delta'] ?? 0 ) + $sPayloadSize,
'metric' => $statsName,
'keygroup' => $keygroup,
'operation' => $op,
];
}
if ( $rPayloadSize > 0 ) {
$statsdName = "objectcache.{$keygroup}.{$op}_bytes_read";
$statsName = "bagostuff_bytes_read_total";
$deltasByMetric[$statsdName] = [
'delta' => ( $deltasByMetric[$statsdName]['delta'] ?? 0 ) + $rPayloadSize,
'metric' => $statsName,
'keygroup' => $keygroup,
'operation' => $op,
];
}
}
foreach ( $deltasByMetric as $statsdName => $delta ) {
$this->stats->getCounter( $delta['metric'] )
->setLabel( 'keygroup', $delta['keygroup'] )
->setLabel( 'operation', $delta['operation'] )
->copyToStatsdAt( $statsdName )
->incrementBy( $delta['delta'] );
}
}
}
/** @deprecated class alias since 1.43 */
class_alias( MediumSpecificBagOStuff::class, 'MediumSpecificBagOStuff' );