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MultiWriteBagOStuff Class Reference

A cache class that replicates all writes to multiple child caches. More...

Inheritance diagram for MultiWriteBagOStuff:
Collaboration diagram for MultiWriteBagOStuff:

Public Member Functions

 __construct ( $params)
 
 add ( $key, $value, $exptime=0, $flags=0)
 Insert an item if it does not already exist. More...
 
 addBusyCallback (callable $workCallback)
 Let a callback be run to avoid wasting time on special blocking calls. More...
 
 changeTTL ( $key, $exptime=0, $flags=0)
 Change the expiration on an item. More...
 
 changeTTLMulti (array $keys, $exptime, $flags=0)
 Change the expiration of multiple items. More...
 
 decr ( $key, $value=1, $flags=0)
 Decrease stored value of $key by $value while preserving its TTL. More...
 
 delete ( $key, $flags=0)
 Delete an item if it exists. More...
 
 deleteMulti (array $keys, $flags=0)
 Delete a batch of items. More...
 
 deleteObjectsExpiringBefore ( $timestamp, callable $progress=null, $limit=INF, string $tag=null)
 Delete all objects expiring before a certain date. More...
 
 get ( $key, $flags=0)
 Get an item. More...
 
 getMulti (array $keys, $flags=0)
 Get a batch of items. More...
 
 incr ( $key, $value=1, $flags=0)
 Increase stored value of $key by $value while preserving its TTL. More...
 
 incrWithInit ( $key, $exptime, $step=1, $init=null, $flags=0)
 Increase the value of the given key (no TTL change) if it exists or create it otherwise. More...
 
 lock ( $key, $timeout=6, $exptime=6, $rclass='')
 Acquire an advisory lock on a key string, exclusive to the caller. More...
 
 makeGlobalKey ( $collection,... $components)
 Make a cache key for the default keyspace and given components. More...
 
 makeKey ( $collection,... $components)
 Make a cache key for the global keyspace and given components. More...
 
 makeKeyInternal ( $keyspace, $components)
 Make a cache key for the given keyspace and components. More...
 
 merge ( $key, callable $callback, $exptime=0, $attempts=10, $flags=0)
 Merge changes into the existing cache value (possibly creating a new one) More...
 
 set ( $key, $value, $exptime=0, $flags=0)
 Set an item. More...
 
 setMockTime (&$time)
 
 setMulti (array $valueByKey, $exptime=0, $flags=0)
 Set a batch of items. More...
 
 setNewPreparedValues (array $valueByKey)
 Stage a set of new key values for storage and estimate the amount of bytes needed. More...
 
 unlock ( $key)
 Release an advisory lock on a key string. More...
 
- Public Member Functions inherited from BagOStuff
 __construct (array $params=[])
 
 clearLastError ()
 Clear the "last error" registry. More...
 
 getCurrentTime ()
 
 getLastError ( $watchPoint=0)
 Get the "last error" registry. More...
 
 getLogger ()
 
 getQoS ( $flag)
 
 getScopedLock ( $key, $timeout=6, $expiry=30, $rclass='')
 Get a lightweight exclusive self-unlocking lock. More...
 
 getSegmentationSize ()
 
 getSegmentedValueMaxSize ()
 
 getWithSetCallback ( $key, $exptime, $callback, $flags=0)
 Get an item, regenerating and setting it if not found. More...
 
 isKeyGlobal ( $key)
 Check whether a cache key is in the global keyspace. More...
 
 registerWrapperInfoForStats (string $prefixComponent, string $statsGroup, callable $collectionCallback)
 Register info about a caching layer class that uses BagOStuff as a backing store. More...
 
 setLogger (LoggerInterface $logger)
 
 watchErrors ()
 Get a "watch point" token that can be used to get the "last error" to occur after now. More...
 

Protected Member Functions

 convertGenericKey ( $key)
 Convert a "generic" reversible cache key into one for this cache. More...
 
- Protected Member Functions inherited from BagOStuff
 componentsFromGenericKey ( $key)
 Extract the components from a "generic" reversible cache key. More...
 
 determineKeyPrefixForStats ( $key)
 
 fieldHasFlags ( $field, $flags)
 
 genericKeyFromComponents (... $components)
 At a minimum, there must be a keyspace and collection name component. More...
 
 mergeFlagMaps (array $bags)
 Merge the flag maps of one or more BagOStuff objects into a "lowest common denominator" map. More...
 
 proxyCall (string $method, int $arg0Sig, int $resSig, array $genericArgs, BagOStuff $wrapper)
 Call a method on behalf of wrapper BagOStuff instance that uses "generic" keys. More...
 
 setLastError ( $error)
 Set the "last error" registry due to a problem encountered during an attempted operation. More...
 

Protected Attributes

bool $asyncWrites = false
 Use async secondary writes. More...
 
int[] $cacheIndexes = []
 List of all backing cache indexes. More...
 
BagOStuff[] $caches
 Backing cache stores in order of highest to lowest tier. More...
 
- Protected Attributes inherited from BagOStuff
callable null $asyncHandler
 
int[] $attrMap = []
 Map of (BagOStuff:ATTR_* constant => BagOStuff:QOS_* constant) More...
 
string $keyspace
 Default keyspace; used by makeKey() More...
 
int $lastError = self::ERR_NONE
 BagOStuff:ERR_* constant of the last error that occurred. More...
 
int $lastErrorId = 0
 Error event sequence number of the last error that occurred. More...
 
LoggerInterface $logger
 
StatsdDataFactoryInterface $stats
 
array< string, array > $wrapperInfoByPrefix = []
 Cache key processing callbacks and info for metrics. More...
 

Additional Inherited Members

- Public Attributes inherited from BagOStuff
const MAX_CONFLICTS_ONE = 1
 Abort after the first merge conflict. More...
 
const READ_LATEST = 1
 Bitfield constants for get()/getMulti(); these are only advisory. More...
 
const READ_VERIFIED = 2
 Promise that the caller handles detection of staleness. More...
 
const WRITE_ALLOW_SEGMENTS = 16
 Allow partitioning of the value if it is large. More...
 
const WRITE_BACKGROUND = 64
 If supported, do not block on write operation completion; instead, treat writes as succesful based on whether they could be buffered. More...
 
const WRITE_CACHE_ONLY = 8
 Bitfield constants for set()/merge(); these are only advisory. More...
 
const WRITE_PRUNE_SEGMENTS = 32
 Delete all the segments if the value is partitioned. More...
 
- Public Attributes inherited from Wikimedia\LightweightObjectStore\StorageAwareness
const ATTR_DURABILITY = 2
 Durability of writes; see QOS_DURABILITY_* (higher means stronger) More...
 
const ATTR_EMULATION = 1
 Emulation/fallback mode; see QOS_EMULATION_*; higher is better. More...
 
const ERR_NO_RESPONSE = 1
 Storage medium failed to yield a complete response to an operation. More...
 
const ERR_NONE = 0
 No storage medium error. More...
 
const ERR_UNEXPECTED = 3
 Storage medium operation failed due to usage limitations or an I/O error. More...
 
const ERR_UNREACHABLE = 2
 Storage medium could not be reached to establish a connection. More...
 
const QOS_DURABILITY_DISK = 4
 Data is saved to disk and writes do not usually block on fsync() More...
 
const QOS_DURABILITY_NONE = 1
 Data is never saved to begin with (blackhole store) More...
 
const QOS_DURABILITY_RDBMS = 5
 Data is saved to disk and writes usually block on fsync(), like a standard RDBMS. More...
 
const QOS_DURABILITY_SCRIPT = 2
 Data is lost at the end of the current web request or CLI script. More...
 
const QOS_DURABILITY_SERVICE = 3
 Data is lost once the service storing the data restarts. More...
 
const QOS_EMULATION_SQL = 1
 Fallback disk-based SQL store. More...
 
const QOS_UNKNOWN = INF
 Generic "unknown" value; useful for comparisons (always "good enough") More...
 
- Static Protected Attributes inherited from BagOStuff
static int $nextErrorMonitorId = 1
 Next sequence number to use for watch/error events. More...
 

Detailed Description

A cache class that replicates all writes to multiple child caches.

Reads are implemented by reading from the caches in the order they are given in the configuration until a cache gives a positive result.

Note that cache key construction will use the first cache backend in the list, so make sure that the other backends can handle such keys (e.g. via encoding).

Stability: newable

Definition at line 36 of file MultiWriteBagOStuff.php.

Constructor & Destructor Documentation

◆ __construct()

MultiWriteBagOStuff::__construct (   $params)
Stability: stable
to call
Parameters
array$params
  • caches: A numbered array of either ObjectFactory::getObjectFromSpec arrays yielding BagOStuff objects or direct BagOStuff objects. If using the former, the 'args' field must be set. The first cache is the primary one, being the first to be read in the fallback chain. Writes happen to all stores in the order they are defined. However, lock()/unlock() calls only use the primary store.
  • replication: Either 'sync' or 'async'. This controls whether writes to secondary stores are deferred when possible. To use 'async' writes requires the 'asyncHandler' option to be set as well. Async writes can increase the chance of some race conditions or cause keys to expire seconds later than expected. It is safe to use for modules when cached values: are immutable, invalidation uses logical TTLs, invalidation uses etag/timestamp validation against the DB, or merge() is used to handle races.
Exceptions
InvalidArgumentException

Definition at line 69 of file MultiWriteBagOStuff.php.

References BagOStuff\mergeFlagMaps().

Member Function Documentation

◆ add()

MultiWriteBagOStuff::add (   $key,
  $value,
  $exptime = 0,
  $flags = 0 
)

Insert an item if it does not already exist.

Parameters
string$key
mixed$value
int$exptime
int$flagsBitfield of BagOStuff::WRITE_* constants (since 1.33)
Returns
bool Success (item created)

Reimplemented from BagOStuff.

Definition at line 179 of file MultiWriteBagOStuff.php.

◆ addBusyCallback()

MultiWriteBagOStuff::addBusyCallback ( callable  $workCallback)

Let a callback be run to avoid wasting time on special blocking calls.

This is hard-deprecated and non-functional since 1.39. The callback will not be called.

Parameters
callable$workCallback
Since
1.28
Deprecated:
since 1.39

Reimplemented from BagOStuff.

Definition at line 356 of file MultiWriteBagOStuff.php.

◆ changeTTL()

MultiWriteBagOStuff::changeTTL (   $key,
  $exptime = 0,
  $flags = 0 
)

Change the expiration on an item.

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.

Parameters
string$key
int$exptimeTTL or UNIX timestamp
int$flagsBitfield of BagOStuff::WRITE_* constants (since 1.33)
Returns
bool Success (item found and updated)
Since
1.28

Reimplemented from BagOStuff.

Definition at line 218 of file MultiWriteBagOStuff.php.

◆ changeTTLMulti()

MultiWriteBagOStuff::changeTTLMulti ( array  $keys,
  $exptime,
  $flags = 0 
)

Change the expiration of multiple items.

See also
BagOStuff::changeTTL()
Parameters
string[]$keysList of keys
int$exptimeTTL or UNIX timestamp
int$flagsBitfield of BagOStuff::WRITE_* constants (since 1.33)
Returns
bool Success (all items found and updated)
Since
1.34

Reimplemented from BagOStuff.

Definition at line 299 of file MultiWriteBagOStuff.php.

◆ convertGenericKey()

MultiWriteBagOStuff::convertGenericKey (   $key)
protected

Convert a "generic" reversible cache key into one for this cache.

See also
BagOStuff::genericKeyFromComponents()
Parameters
string$keyKeyspace-prepended list of encoded components as a colon-separated value
Returns
string Keyspace-prepended list of encoded components as a colon-separated value

Reimplemented from BagOStuff.

Definition at line 351 of file MultiWriteBagOStuff.php.

◆ decr()

MultiWriteBagOStuff::decr (   $key,
  $value = 1,
  $flags = 0 
)

Decrease stored value of $key by $value while preserving its TTL.

Parameters
string$key
int$valueValue to subtract from $key (default: 1) [optional]
int$flagsBit field of class WRITE_* constants [optional]
Returns
int|bool New value or false on failure
Deprecated:
Since 1.38

Reimplemented from BagOStuff.

Definition at line 319 of file MultiWriteBagOStuff.php.

◆ delete()

MultiWriteBagOStuff::delete (   $key,
  $flags = 0 
)

Delete an item if it exists.

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.

Parameters
string$key
int$flagsBitfield of BagOStuff::WRITE_* constants
Returns
bool Success (item deleted or not found)

Reimplemented from BagOStuff.

Definition at line 169 of file MultiWriteBagOStuff.php.

◆ deleteMulti()

MultiWriteBagOStuff::deleteMulti ( array  $keys,
  $flags = 0 
)

Delete a batch of items.

This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O

WRITE_BACKGROUND can be used for bulk deletion where the response is not vital

Parameters
string[]$keysList of keys
int$flagsBitfield of BagOStuff::WRITE_* constants
Returns
bool Success (items deleted and/or not found)
Since
1.33

Reimplemented from BagOStuff.

Definition at line 289 of file MultiWriteBagOStuff.php.

◆ deleteObjectsExpiringBefore()

MultiWriteBagOStuff::deleteObjectsExpiringBefore (   $timestamp,
callable  $progress = null,
  $limit = INF,
string  $tag = null 
)

Delete all objects expiring before a certain date.

Parameters
string | int$timestampThe reference date in MW or TS_UNIX format
callable | null$progressOptional, a function which will be called regularly during long-running operations with the percentage progress as the first parameter. [optional]
int | float$limitMaximum number of keys to delete [default: INF]
string | null$tagTag to purge a single shard only. This is only supported when server tags are used in configuration.
Returns
bool Success; false if unimplemented

Reimplemented from BagOStuff.

Definition at line 250 of file MultiWriteBagOStuff.php.

References $cache.

◆ get()

MultiWriteBagOStuff::get (   $key,
  $flags = 0 
)

Get an item.

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.

Parameters
string$key
int$flagsBitfield of BagOStuff::READ_* constants [optional]
Returns
mixed Returns false on failure or if the item does not exist

Reimplemented from BagOStuff.

Definition at line 108 of file MultiWriteBagOStuff.php.

References $args, and BagOStuff\fieldHasFlags().

◆ getMulti()

MultiWriteBagOStuff::getMulti ( array  $keys,
  $flags = 0 
)

Get a batch of items.

Parameters
string[]$keysList of keys
int$flagsBitfield; supports READ_LATEST [optional]
Returns
mixed[] Map of (key => value) for existing keys

Reimplemented from BagOStuff.

Definition at line 266 of file MultiWriteBagOStuff.php.

References $keys, and $res.

◆ incr()

MultiWriteBagOStuff::incr (   $key,
  $value = 1,
  $flags = 0 
)

Increase stored value of $key by $value while preserving its TTL.

Parameters
string$keyKey to increase
int$valueValue to add to $key (default: 1) [optional]
int$flagsBit field of class WRITE_* constants [optional]
Returns
int|bool New value or false on failure
Deprecated:
Since 1.38

Reimplemented from BagOStuff.

Definition at line 309 of file MultiWriteBagOStuff.php.

◆ incrWithInit()

MultiWriteBagOStuff::incrWithInit (   $key,
  $exptime,
  $step = 1,
  $init = null,
  $flags = 0 
)

Increase the value of the given key (no TTL change) if it exists or create it otherwise.

This will create the key with the value $init and TTL $exptime instead if not present. Callers should make sure that both ($init - $step) and $exptime are invariants for all operations to any given key. The value of $init should be at least that of $step.

The new value is returned, except if the WRITE_BACKGROUND flag is given, in which case the handler may choose to return true to indicate that the operation has been dispatched.

Parameters
string$keyKey built via makeKey() or makeGlobalKey()
int$exptimeTime-to-live (in seconds) or a UNIX timestamp expiration
int$stepAmount to increase the key value by [default: 1]
int | null$initValue to initialize the key to if it does not exist [default: $step]
int$flagsBit field of class WRITE_* constants [optional]
Returns
int|bool New value (or true if asynchronous) on success; false on failure
Since
1.24

Reimplemented from BagOStuff.

Definition at line 329 of file MultiWriteBagOStuff.php.

◆ lock()

MultiWriteBagOStuff::lock (   $key,
  $timeout = 6,
  $exptime = 6,
  $rclass = '' 
)

Acquire an advisory lock on a key string, exclusive to the caller.

Parameters
string$key
int$timeoutLock wait timeout; 0 for non-blocking [optional]
int$exptimeLock time-to-live in seconds; 1 day maximum [optional]
string$rclassIf this thread already holds the lock, and the lock was acquired using the same value for this parameter, then return true and use reference counting so that only the unlock() call from the outermost lock() caller actually releases the lock (note that only the outermost time-to-live is used) [optional]
Returns
bool Success

Reimplemented from BagOStuff.

Definition at line 228 of file MultiWriteBagOStuff.php.

◆ makeGlobalKey()

MultiWriteBagOStuff::makeGlobalKey (   $collection,
  $components 
)

Make a cache key for the default keyspace and given components.

See also
IStoreKeyEncoder::makeGlobalKey()
Parameters
string$collectionKey collection name component
string|int...$components Additional, ordered, key components for entity IDs
Returns
string Colon-separated, keyspace-prepended, ordered list of encoded components
Since
1.27

Reimplemented from BagOStuff.

Definition at line 347 of file MultiWriteBagOStuff.php.

References BagOStuff\genericKeyFromComponents().

◆ makeKey()

MultiWriteBagOStuff::makeKey (   $collection,
  $components 
)

Make a cache key for the global keyspace and given components.

See also
IStoreKeyEncoder::makeKey()
Parameters
string$collectionKey collection name component
string|int...$components Additional, ordered, key components for entity IDs
Returns
string Colon-separated, keyspace-prepended, ordered list of encoded components
Since
1.27

Reimplemented from BagOStuff.

Definition at line 343 of file MultiWriteBagOStuff.php.

References BagOStuff\genericKeyFromComponents().

◆ makeKeyInternal()

MultiWriteBagOStuff::makeKeyInternal (   $keyspace,
  $components 
)

Make a cache key for the given keyspace and components.

Long components might be converted to respective hashes due to size constraints. In extreme cases, all of them might be combined into a single hash component.

Access: internal
This method should not be used outside of BagOStuff (since 1.36)
Parameters
string$keyspaceKeyspace component
string[] | int[]$componentsKey components (key collection name first)
Returns
string Keyspace-prepended list of encoded components as a colon-separated value
Since
1.27

Reimplemented from BagOStuff.

Definition at line 339 of file MultiWriteBagOStuff.php.

References BagOStuff\$keyspace, and BagOStuff\genericKeyFromComponents().

◆ merge()

MultiWriteBagOStuff::merge (   $key,
callable  $callback,
  $exptime = 0,
  $attempts = 10,
  $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.

Parameters
string$key
callable$callbackCallback method to be executed
int$exptimeEither an interval in seconds or a unix timestamp for expiry
int$attemptsThe amount of times to attempt a merge in case of failure
int$flagsBitfield of BagOStuff::WRITE_* constants
Returns
bool Success
Exceptions
InvalidArgumentException

Reimplemented from BagOStuff.

Definition at line 208 of file MultiWriteBagOStuff.php.

◆ set()

MultiWriteBagOStuff::set (   $key,
  $value,
  $exptime = 0,
  $flags = 0 
)

Set an item.

Parameters
string$key
mixed$value
int$exptimeEither an interval in seconds or a unix timestamp for expiry
int$flagsBitfield of BagOStuff::WRITE_* constants
Returns
bool Success

Reimplemented from BagOStuff.

Definition at line 159 of file MultiWriteBagOStuff.php.

◆ setMockTime()

MultiWriteBagOStuff::setMockTime ( $time)
Access: internal
For testing only
Parameters
float | null&$timeMock UNIX timestamp

Reimplemented from BagOStuff.

Definition at line 370 of file MultiWriteBagOStuff.php.

References $cache.

◆ setMulti()

MultiWriteBagOStuff::setMulti ( array  $valueByKey,
  $exptime = 0,
  $flags = 0 
)

Set a batch of items.

This does not support WRITE_ALLOW_SEGMENTS to avoid excessive read I/O

WRITE_BACKGROUND can be used for bulk insertion where the response is not vital

Parameters
mixed[]$valueByKeyMap of (key => value)
int$exptimeEither an interval in seconds or a unix timestamp for expiry
int$flagsBitfield of BagOStuff::WRITE_* constants (since 1.33)
Returns
bool Success
Since
1.24

Reimplemented from BagOStuff.

Definition at line 279 of file MultiWriteBagOStuff.php.

◆ setNewPreparedValues()

MultiWriteBagOStuff::setNewPreparedValues ( array  $valueByKey)

Stage a set of new key values for storage and estimate the amount of bytes needed.

All previously prepared values will be cleared. Each of the new prepared values will be individually cleared as they get used by write operations for that key. This is done to avoid unchecked growth in PHP memory usage.

Example usage:

$valueByKey = [ $key1 => $value1, $key2 => $value2, $key3 => $value3 ];
$cache->setNewPreparedValues( $valueByKey );
$cache->set( $key1, $value1, $cache::TTL_HOUR );
$cache->setMulti( [ $key2 => $value2, $key3 => $value3 ], $cache::TTL_HOUR );
$cache
Definition: mcc.php:33

This is only useful if the caller needs an estimate of the serialized object sizes, such as cache wrappers with adaptive write slam avoidance or store wrappers with metrics. The caller cannot know the serialization format and even if it did, it could be expensive to serialize complex values twice just to get the size information before writing them to cache. This method solves both problems by making the cache instance do the serialization and having it reuse the result when the cache write happens.

Parameters
array$valueByKeyMap of (cache key => PHP variable value to serialize)
Returns
int[]|null[] Corresponding list of size estimates (null for invalid values)
Since
1.35

Reimplemented from BagOStuff.

Definition at line 360 of file MultiWriteBagOStuff.php.

◆ unlock()

MultiWriteBagOStuff::unlock (   $key)

Release an advisory lock on a key string.

Parameters
string$key
Returns
bool Success

Reimplemented from BagOStuff.

Definition at line 239 of file MultiWriteBagOStuff.php.

Member Data Documentation

◆ $asyncWrites

bool MultiWriteBagOStuff::$asyncWrites = false
protected

Use async secondary writes.

Definition at line 41 of file MultiWriteBagOStuff.php.

◆ $cacheIndexes

int [] MultiWriteBagOStuff::$cacheIndexes = []
protected

List of all backing cache indexes.

Definition at line 43 of file MultiWriteBagOStuff.php.

◆ $caches

BagOStuff [] MultiWriteBagOStuff::$caches
protected

Backing cache stores in order of highest to lowest tier.

Definition at line 38 of file MultiWriteBagOStuff.php.


The documentation for this class was generated from the following file: