* For any given instance, methods like lock(), unlock(), merge(), and set() with WRITE_SYNC
* should semantically operate over its entire access scope; any nodes/threads in that scope
* should serialize appropriately when using them. Likewise, a call to get() with READ_LATEST
- * from one node in its access scope should reflect the prior changes of any other node its access
- * scope. Any get() should reflect the changes of any prior set() with WRITE_SYNC.
+ * from one node in its access scope should reflect the prior changes of any other node its
+ * access scope. Any get() should reflect the changes of any prior set() with WRITE_SYNC.
+ *
+ * Subclasses should override the default "segmentationSize" field with an appropriate value.
+ * The value should not be larger than what the storage backend (by default) supports. It also
+ * should be roughly informed by common performance bottlenecks (e.g. values over a certain size
+ * having poor scalability). The same goes for the "segmentedValueMaxSize" member, which limits
+ * the maximum size and chunk count (indirectly) of values.
*
* @ingroup Cache
*/
protected $asyncHandler;
/** @var int Seconds */
protected $syncTimeout;
+ /** @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 bool */
private $debugMode = false;
/** Bitfield constants for set()/merge() */
const WRITE_SYNC = 4; // synchronously write to all locations for replicated stores
const WRITE_CACHE_ONLY = 8; // Only change state of the in-memory cache
+ const WRITE_ALLOW_SEGMENTS = 16; // Allow partitioning of the value if it is large
+ const WRITE_PRUNE_SEGMENTS = 32; // Delete all partition segments of the value
+
+ /** @var string Component to use for key construction of blob segment keys */
+ const SEGMENT_COMPONENT = 'segment';
/**
* $params include:
* - reportDupes: Whether to emit warning log messages for all keys that were
* requested more than once (requires an asyncHandler).
* - syncTimeout: How long to wait with WRITE_SYNC in seconds.
+ * - 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
*/
public function __construct( array $params = [] ) {
}
$this->syncTimeout = $params['syncTimeout'] ?? 3;
+ $this->segmentationSize = $params['segmentationSize'] ?? 8388608; // 8MiB
+ $this->segmentedValueMaxSize = $params['segmentedValueMaxSize'] ?? 67108864; // 64MiB
}
/**
/**
* Get an item with the given key, regenerating and setting it if not found
*
- * If the callback returns false, then nothing is stored.
+ * Nothing is stored nor deleted if the callback returns false
*
* @param string $key
* @param int $ttl Time-to-live (seconds)
*
* @param string $key
* @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
- * @param int|null $oldFlags [unused]
- * @return mixed Returns false on failure and if the item does not exist
+ * @return mixed Returns false on failure or if the item does not exist
*/
- public function get( $key, $flags = 0, $oldFlags = null ) {
- // B/C for ( $key, &$casToken = null, $flags = 0 )
- $flags = is_int( $oldFlags ) ? $oldFlags : $flags;
-
+ public function get( $key, $flags = 0 ) {
$this->trackDuplicateKeys( $key );
- return $this->doGet( $key, $flags );
+ return $this->resolveSegments( $key, $this->doGet( $key, $flags ) );
}
/**
/**
* @param string $key
* @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
- * @return mixed Returns false on failure and if the item does not exist
+ * @param mixed|null &$casToken Token to use for check-and-set comparisons
+ * @return mixed Returns false on failure or if the item does not exist
*/
- abstract protected function doGet( $key, $flags = 0 );
+ abstract protected function doGet( $key, $flags = 0, &$casToken = null );
/**
- * @note This method is only needed if merge() uses mergeViaCas()
+ * Set an item
*
* @param string $key
- * @param mixed &$casToken
- * @param int $flags Bitfield of BagOStuff::READ_* constants [optional]
- * @return mixed Returns false on failure and if the item does not exist
- * @throws Exception
+ * @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 getWithToken( $key, &$casToken, $flags = 0 ) {
- throw new Exception( __METHOD__ . ' not implemented.' );
+ public function set( $key, $value, $exptime = 0, $flags = 0 ) {
+ if (
+ ( $flags & self::WRITE_ALLOW_SEGMENTS ) != self::WRITE_ALLOW_SEGMENTS ||
+ is_infinite( $this->segmentationSize )
+ ) {
+ return $this->doSet( $key, $value, $exptime, $flags );
+ }
+
+ $serialized = $this->serialize( $value );
+ $segmentSize = $this->getSegmentationSize();
+ $maxTotalSize = $this->getSegmentedValueMaxSize();
+
+ $size = strlen( $serialized );
+ if ( $size <= $segmentSize ) {
+ // Since the work of serializing it was already done, just use it inline
+ return $this->doSet(
+ $key,
+ SerializedValueContainer::newUnified( $serialized ),
+ $exptime,
+ $flags
+ );
+ } elseif ( $size > $maxTotalSize ) {
+ $this->setLastError( "Key $key exceeded $maxTotalSize bytes." );
+
+ return false;
+ }
+
+ $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;
+ }
+
+ $ok = $this->setMulti( $chunksByKey, $exptime, $flags );
+ if ( $ok ) {
+ // Only when all segments are stored should the main key be changed
+ $ok = $this->doSet(
+ $key,
+ SerializedValueContainer::newSegmented( $segmentHashes ),
+ $exptime,
+ $flags
+ );
+ }
+
+ return $ok;
}
/**
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
* @return bool Success
*/
- abstract public function set( $key, $value, $exptime = 0, $flags = 0 );
+ abstract protected function doSet( $key, $value, $exptime = 0, $flags = 0 );
+
+ /**
+ * Delete an item
+ *
+ * For large values written using WRITE_ALLOW_SEGMENTS, this only deletes the main
+ * segment list key unless WRITE_PRUNE_SEGMENTS is in the flags. While deleting the segment
+ * list key has the effect of functionally deleting the key, it leaves unused blobs in cache.
+ *
+ * @param string $key
+ * @return bool True if the item was deleted or not found, false on failure
+ * @param int $flags Bitfield of BagOStuff::WRITE_* constants
+ */
+ public function delete( $key, $flags = 0 ) {
+ if ( ( $flags & self::WRITE_PRUNE_SEGMENTS ) != self::WRITE_PRUNE_SEGMENTS ) {
+ return $this->doDelete( $key, $flags );
+ }
+
+ $mainValue = $this->doGet( $key, self::READ_LATEST );
+ if ( !$this->doDelete( $key, $flags ) ) {
+ return false;
+ }
+
+ if ( !SerializedValueContainer::isSegmented( $mainValue ) ) {
+ return true; // no segments to delete
+ }
+
+ $orderedKeys = array_map(
+ function ( $segmentHash ) use ( $key ) {
+ return $this->makeGlobalKey( self::SEGMENT_COMPONENT, $key, $segmentHash );
+ },
+ $mainValue->{SerializedValueContainer::SEGMENTED_HASHES}
+ );
+
+ return $this->deleteMulti( $orderedKeys, $flags );
+ }
/**
* Delete an item
* @return bool True if the item was deleted or not found, false on failure
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
*/
- abstract public function delete( $key, $flags = 0 );
+ abstract protected function doDelete( $key, $flags = 0 );
+
+ /**
+ * 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 public function add( $key, $value, $exptime = 0, $flags = 0 );
/**
* Merge changes into the existing cache value (possibly creating a new one)
* (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 overriden in the callback.
+ * Nothing is stored nor deleted if the callback returns false.
*
* @param string $key
* @param callable $callback Callback method to be executed
* @throws InvalidArgumentException
*/
public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
- return $this->mergeViaLock( $key, $callback, $exptime, $attempts, $flags );
+ return $this->mergeViaCas( $key, $callback, $exptime, $attempts, $flags );
}
/**
*/
protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
do {
- $this->clearLastError();
- $reportDupes = $this->reportDupes;
- $this->reportDupes = false;
$casToken = null; // passed by reference
- $currentValue = $this->getWithToken( $key, $casToken, self::READ_LATEST );
- $this->reportDupes = $reportDupes;
-
+ // Get the old value and CAS token from cache
+ $this->clearLastError();
+ $currentValue = $this->resolveSegments(
+ $key,
+ $this->doGet( $key, self::READ_LATEST, $casToken )
+ );
if ( $this->getLastError() ) {
$this->logger->warning(
__METHOD__ . ' failed due to I/O error on get() for {key}.',
// Derive the new value from the old value
$value = call_user_func( $callback, $this, $key, $currentValue, $exptime );
+ $hadNoCurrentValue = ( $currentValue === false );
+ unset( $currentValue ); // free RAM in case the value is large
$this->clearLastError();
if ( $value === false ) {
$success = true; // do nothing
- } elseif ( $currentValue === false ) {
+ } elseif ( $hadNoCurrentValue ) {
// Try to create the key, failing if it gets created in the meantime
$success = $this->add( $key, $value, $exptime, $flags );
} else {
return false; // IO error; don't spam retries
}
+
} while ( !$success && --$attempts );
return $success;
* @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
- * @throws Exception
*/
protected function cas( $casToken, $key, $value, $exptime = 0, $flags = 0 ) {
if ( !$this->lock( $key, 0 ) ) {
}
$curCasToken = null; // passed by reference
- $this->getWithToken( $key, $curCasToken, self::READ_LATEST );
+ $this->doGet( $key, self::READ_LATEST, $curCasToken );
if ( $casToken === $curCasToken ) {
$success = $this->set( $key, $value, $exptime, $flags );
} else {
}
/**
- * @see BagOStuff::merge()
+ * 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 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
+ * @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
*/
- protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
- if ( $attempts <= 1 ) {
- $timeout = 0; // clearly intended to be "non-blocking"
- } else {
- $timeout = 3;
- }
+ public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
+ $expiry = $this->convertToExpiry( $exptime );
+ $delete = ( $expiry != 0 && $expiry < $this->getCurrentTime() );
- if ( !$this->lock( $key, $timeout ) ) {
+ if ( !$this->lock( $key, 0 ) ) {
return false;
}
-
- $this->clearLastError();
- $reportDupes = $this->reportDupes;
- $this->reportDupes = false;
- $currentValue = $this->get( $key, self::READ_LATEST );
- $this->reportDupes = $reportDupes;
-
- if ( $this->getLastError() ) {
- $this->logger->warning(
- __METHOD__ . ' failed due to I/O error on get() for {key}.',
- [ 'key' => $key ]
- );
-
- $success = false;
- } else {
- // Derive the new value from the old value
- $value = call_user_func( $callback, $this, $key, $currentValue, $exptime );
- if ( $value === false ) {
- $success = true; // do nothing
+ // 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 {
- $success = $this->set( $key, $value, $exptime, $flags ); // set the new value
+ $ok = $this->doSet( $key, $blob, $exptime, $flags );
}
+ } else {
+ $ok = false;
}
- if ( !$this->unlock( $key ) ) {
- // this should never happen
- trigger_error( "Could not release lock for key '$key'." );
- }
-
- return $success;
- }
-
- /**
- * Reset the TTL on a key if it exists
- *
- * @param string $key
- * @param int $expiry
- * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
- * @return bool Success Returns false if there is no key
- * @since 1.28
- */
- public function changeTTL( $key, $expiry = 0, $flags = 0 ) {
- $value = $this->get( $key );
+ $this->unlock( $key );
- return ( $value === false ) ? false : $this->set( $key, $value, $expiry, $flags );
+ return $ok;
}
/**
* @return bool Success
*/
public function unlock( $key ) {
- if ( isset( $this->locks[$key] ) && --$this->locks[$key]['depth'] <= 0 ) {
+ if ( !isset( $this->locks[$key] ) ) {
+ return false;
+ }
+
+ if ( --$this->locks[$key]['depth'] <= 0 ) {
unset( $this->locks[$key] );
- $ok = $this->delete( "{$key}:lock" );
+ $ok = $this->doDelete( "{$key}:lock" );
if ( !$ok ) {
$this->logger->warning(
__METHOD__ . ' failed to release lock for {key}.',
* @return array
*/
public function getMulti( array $keys, $flags = 0 ) {
+ $valuesBykey = $this->doGetMulti( $keys, $flags );
+ foreach ( $valuesBykey as $key => $value ) {
+ // Resolve one blob at a time (avoids too much I/O at once)
+ $valuesBykey[$key] = $this->resolveSegments( $key, $value );
+ }
+
+ return $valuesBykey;
+ }
+
+ /**
+ * 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
+ */
+ protected function doGetMulti( array $keys, $flags = 0 ) {
$res = [];
foreach ( $keys as $key ) {
- $val = $this->get( $key, $flags );
+ $val = $this->doGet( $key, $flags );
if ( $val !== false ) {
$res[$key] = $val;
}
/**
* Batch insertion/replace
+ *
+ * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
+ *
* @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 (since 1.33)
* @since 1.24
*/
public function setMulti( array $data, $exptime = 0, $flags = 0 ) {
+ if ( ( $flags & self::WRITE_ALLOW_SEGMENTS ) === self::WRITE_ALLOW_SEGMENTS ) {
+ throw new InvalidArgumentException( __METHOD__ . ' got WRITE_ALLOW_SEGMENTS' );
+ }
+
$res = true;
foreach ( $data as $key => $value ) {
- if ( !$this->set( $key, $value, $exptime, $flags ) ) {
- $res = false;
- }
+ $res = $this->doSet( $key, $value, $exptime, $flags ) && $res;
}
return $res;
/**
* Batch deletion
+ *
+ * This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O
+ *
* @param string[] $keys List of keys
* @param int $flags Bitfield of BagOStuff::WRITE_* constants
* @return bool Success
public function deleteMulti( array $keys, $flags = 0 ) {
$res = true;
foreach ( $keys as $key ) {
- $res = $this->delete( $key, $flags ) && $res;
+ $res = $this->doDelete( $key, $flags ) && $res;
}
return $res;
}
- /**
- * Insertion
- * @param string $key
- * @param mixed $value
- * @param int $exptime
- * @param int $flags Bitfield of BagOStuff::WRITE_* constants (since 1.33)
- * @return bool Success
- */
- public function add( $key, $value, $exptime = 0, $flags = 0 ) {
- // @note: avoid lock() here since that method uses *this* method by default
- if ( $this->get( $key ) === false ) {
- return $this->set( $key, $value, $exptime, $flags );
- }
-
- return false; // key already set
- }
-
/**
* Increase stored value of $key by $value while preserving its TTL
* @param string $key Key to increase
- * @param int $value Value to add to $key (Default 1)
+ * @param int $value Value to add to $key (default: 1) [optional]
* @return int|bool New value or false on failure
*/
- public function incr( $key, $value = 1 ) {
- if ( !$this->lock( $key, 1 ) ) {
- return false;
- }
- $n = $this->get( $key, self::READ_LATEST );
- if ( $this->isInteger( $n ) ) { // key exists?
- $n += intval( $value );
- $this->set( $key, max( 0, $n ) ); // exptime?
- } else {
- $n = false;
- }
- $this->unlock( $key );
-
- return $n;
- }
+ abstract public function incr( $key, $value = 1 );
/**
* Decrease stored value of $key by $value while preserving its TTL
* @param string $key
- * @param int $value
+ * @param int $value Value to subtract from $key (default: 1) [optional]
* @return int|bool New value or false on failure
*/
public function decr( $key, $value = 1 ) {
return $newValue;
}
+ /**
+ * 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
+ */
+ protected function resolveSegments( $key, $mainValue ) {
+ if ( SerializedValueContainer::isUnified( $mainValue ) ) {
+ return $this->unserialize( $mainValue->{SerializedValueContainer::UNIFIED_DATA} );
+ }
+
+ 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 {
+ return false; // missing segment
+ }
+ }
+
+ return $this->unserialize( implode( '', $parts ) );
+ }
+
+ return $mainValue;
+ }
+
/**
* Get the "last error" registered; clearLastError() should be called manually
* @return int ERR_* constant for the "last error" registry
}
}
+ /**
+ * @param int $exptime
+ * @return bool
+ */
+ protected function expiryIsRelative( $exptime ) {
+ return ( $exptime != 0 && $exptime < ( 10 * self::TTL_YEAR ) );
+ }
+
/**
* Convert an optionally relative time to an absolute time
* @param int $exptime
* @return int
*/
- protected function convertExpiry( $exptime ) {
- if ( $exptime != 0 && $exptime < ( 10 * self::TTL_YEAR ) ) {
+ protected function convertToExpiry( $exptime ) {
+ if ( $this->expiryIsRelative( $exptime ) ) {
return (int)$this->getCurrentTime() + $exptime;
} else {
return $exptime;
* @return bool
*/
protected function isInteger( $value ) {
- return ( is_int( $value ) || ctype_digit( $value ) );
+ if ( is_int( $value ) ) {
+ return true;
+ } elseif ( !is_string( $value ) ) {
+ return false;
+ }
+
+ $integer = (int)$value;
+
+ return ( $value === (string)$integer );
}
/**
return $this->attrMap[$flag] ?? self::QOS_UNKNOWN;
}
+ /**
+ * @return int|float The chunk size, in bytes, of segmented objects (INF for no limit)
+ * @since 1.34
+ */
+ public function getSegmentationSize() {
+ return $this->segmentationSize;
+ }
+
+ /**
+ * @return int|float Maximum total segmented object size in bytes (INF for no limit)
+ * @since 1.34
+ */
+ public function getSegmentedValueMaxSize() {
+ return $this->segmentedValueMaxSize;
+ }
+
/**
* Merge the flag maps of one or more BagOStuff objects into a "lowest common denominator" map
*
}
/**
+ * @internal For testing only
* @return float UNIX timestamp
* @codeCoverageIgnore
*/
- protected function getCurrentTime() {
+ public function getCurrentTime() {
return $this->wallClockOverride ?: microtime( true );
}
/**
- * @param float|null &$time Mock UNIX timestamp for testing
+ * @internal For testing only
+ * @param float|null &$time Mock UNIX timestamp
* @codeCoverageIgnore
*/
public function setMockTime( &$time ) {
$this->wallClockOverride =& $time;
}
+
+ /**
+ * @param mixed $value
+ * @return string|int 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 $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 );
+ }
}
dépôts / lhc / web / wiklou.git / blobdiff