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ReplicatedBagOStuff Class Reference

A cache class that directs writes to one set of servers and reads to another. More...

Inherits BagOStuff.

Collaboration diagram for ReplicatedBagOStuff:

Public Member Functions

 __construct ( $params)
 Constructor.
 
 add ( $key, $value, $exptime=0, $flags=0)
 Insert an item if it does not already exist.
 
 changeTTL ( $key, $exptime=0, $flags=0)
 Change the expiration on an item.
 
 changeTTLMulti (array $keys, $exptime, $flags=0)
 Change the expiration of multiple items.
 
 delete ( $key, $flags=0)
 Delete an item if it exists.
 
 deleteMulti (array $keys, $flags=0)
 Delete a batch of items.
 
 deleteObjectsExpiringBefore ( $timestamp, callable $progress=null, $limit=INF, string $tag=null)
 Delete all objects expiring before a certain date.
 
 get ( $key, $flags=0)
 Get an item.
 
 getMulti (array $keys, $flags=0)
 Get a batch of items.
 
 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.
 
 lock ( $key, $timeout=6, $exptime=6, $rclass='')
 Acquire an advisory lock on a key string, exclusive to the caller.
 
 merge ( $key, callable $callback, $exptime=0, $attempts=10, $flags=0)
 Merge changes into the existing cache value (possibly creating a new one)
 
 set ( $key, $value, $exptime=0, $flags=0)
 Set an item.
 
 setMockTime (&$time)
 
 setMulti (array $valueByKey, $exptime=0, $flags=0)
 Set a batch of items.
 
 unlock ( $key)
 Release an advisory lock on a key string.
 
- Public Member Functions inherited from BagOStuff
 __construct (array $params=[])
 
 clearLastError ()
 Clear the "last error" registry.
 
 getCurrentTime ()
 
 getLastError ( $watchPoint=0)
 Get the "last error" registry.
 
 getLogger ()
 
 getQoS ( $flag)
 
 getScopedLock ( $key, $timeout=6, $exptime=30, $rclass='')
 Get a lightweight exclusive self-unlocking lock.
 
 getSegmentationSize ()
 
 getSegmentedValueMaxSize ()
 
 getWithSetCallback ( $key, $exptime, $callback, $flags=0)
 Get an item, regenerating and setting it if not found.
 
 isKeyGlobal ( $key)
 Check whether a cache key is in the global keyspace.
 
 makeGlobalKey ( $keygroup,... $components)
 Make a cache key from the given components, in the "global" keyspace.
 
 makeKey ( $keygroup,... $components)
 Make a cache key from the given components, in the default keyspace.
 
 setLogger (LoggerInterface $logger)
 
 setNewPreparedValues (array $valueByKey)
 Stage a set of new key values for storage and estimate the amount of bytes needed.
 
 watchErrors ()
 Get a "watch point" token that can be used to get the "last error" to occur after now.
 

Additional Inherited Members

- Public Attributes inherited from BagOStuff
const MAX_CONFLICTS_ONE = 1
 Abort after the first merge conflict.
 
const READ_LATEST = 1
 Bitfield constants for get()/getMulti(); these are only advisory.
 
const READ_VERIFIED = 2
 Promise that the caller handles detection of staleness.
 
const WRITE_ALLOW_SEGMENTS = 16
 Allow partitioning of the value if it is a large string.
 
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.
 
const WRITE_CACHE_ONLY = 8
 Bitfield constants for set()/merge(); these are only advisory.
 
const WRITE_PRUNE_SEGMENTS = 32
 Delete all the segments if the value is partitioned.
 
- Public Attributes inherited from Wikimedia\LightweightObjectStore\StorageAwareness
const ATTR_DURABILITY = 2
 Durability of writes; see QOS_DURABILITY_* (higher means stronger)
 
const ATTR_EMULATION = 1
 
const ERR_NO_RESPONSE = 1
 Storage medium failed to yield a complete response to an operation.
 
const ERR_NONE = 0
 No storage medium error.
 
const ERR_UNEXPECTED = 3
 Storage medium operation failed due to usage limitations or an I/O error.
 
const ERR_UNREACHABLE = 2
 Storage medium could not be reached to establish a connection.
 
const QOS_DURABILITY_DISK = 4
 Data is saved to disk and writes do not usually block on fsync()
 
const QOS_DURABILITY_NONE = 1
 Data is never saved to begin with (blackhole store)
 
const QOS_DURABILITY_RDBMS = 5
 Data is saved to disk and writes usually block on fsync(), like a standard RDBMS.
 
const QOS_DURABILITY_SCRIPT = 2
 Data is lost at the end of the current web request or CLI script.
 
const QOS_DURABILITY_SERVICE = 3
 Data is lost once the service storing the data restarts.
 
const QOS_EMULATION_SQL = 1
 
const QOS_UNKNOWN = INF
 Generic "unknown" value; useful for comparisons (always "good enough")
 
- Protected Member Functions inherited from BagOStuff
 determineKeyPrefixForStats ( $key)
 
 fieldHasFlags ( $field, $flags)
 
 makeKeyInternal ( $keyspace, $components)
 Make a cache key for the given keyspace and components.
 
 mergeFlagMaps (array $bags)
 Merge the flag maps of one or more BagOStuff objects into a "lowest common denominator" map.
 
 proxyCall (string $method, int $arg0Sig, int $resSig, array $genericArgs, BagOStuff $wrapper)
 Call a method on behalf of wrapper BagOStuff instance.
 
 requireConvertGenericKey ()
 Whether ::proxyCall() must re-encode cache keys before calling read/write methods.
 
 setLastError ( $error)
 Set the "last error" registry due to a problem encountered during an attempted operation.
 
- Protected Attributes inherited from BagOStuff
callable null $asyncHandler
 
int[] $attrMap = []
 Map of (BagOStuff:ATTR_* constant => BagOStuff:QOS_* constant)
 
string $keyspace
 Default keyspace; used by makeKey()
 
int $lastError = self::ERR_NONE
 BagOStuff:ERR_* constant of the last error that occurred.
 
int $lastErrorId = 0
 Error event sequence number of the last error that occurred.
 
LoggerInterface $logger
 
StatsdDataFactoryInterface $stats
 
- Static Protected Attributes inherited from BagOStuff
static int $nextErrorMonitorId = 1
 Next sequence number to use for watch/error events.
 

Detailed Description

A cache class that directs writes to one set of servers and reads to another.

This assumes that the servers used for reads are setup to replica DB those that writes go to. This can easily be used with redis for example.

In the WAN scenario (e.g. multi-datacenter case), this is useful when writes are rare or they usually take place in the primary datacenter.

Deprecated:
since 1.42
Since
1.26

Definition at line 35 of file ReplicatedBagOStuff.php.

Constructor & Destructor Documentation

◆ __construct()

ReplicatedBagOStuff::__construct (   $params)

Constructor.

Parameters are:

  • writeFactory: ObjectFactory::getObjectFromSpec array yielding BagOStuff. This object will be used for writes (e.g. the primary DB).
  • readFactory: ObjectFactory::getObjectFromSpec array yielding BagOStuff. This object will be used for reads (e.g. a replica DB).
  • sessionConsistencyWindow: Seconds to read from the master source for a key after writing to it. [Default: ReplicatedBagOStuff::MAX_WRITE_DELAY]
Deprecated:
since 1.42
Parameters
array$params
Exceptions
InvalidArgumentException

Definition at line 62 of file ReplicatedBagOStuff.php.

References BagOStuff\mergeFlagMaps().

Member Function Documentation

◆ add()

ReplicatedBagOStuff::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 126 of file ReplicatedBagOStuff.php.

◆ changeTTL()

ReplicatedBagOStuff::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 150 of file ReplicatedBagOStuff.php.

◆ changeTTLMulti()

ReplicatedBagOStuff::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 240 of file ReplicatedBagOStuff.php.

◆ delete()

ReplicatedBagOStuff::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 114 of file ReplicatedBagOStuff.php.

◆ deleteMulti()

ReplicatedBagOStuff::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 228 of file ReplicatedBagOStuff.php.

◆ deleteObjectsExpiringBefore()

ReplicatedBagOStuff::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 182 of file ReplicatedBagOStuff.php.

◆ get()

ReplicatedBagOStuff::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 83 of file ReplicatedBagOStuff.php.

References BagOStuff\fieldHasFlags().

◆ getMulti()

ReplicatedBagOStuff::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 197 of file ReplicatedBagOStuff.php.

References BagOStuff\fieldHasFlags().

◆ incrWithInit()

ReplicatedBagOStuff::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 252 of file ReplicatedBagOStuff.php.

◆ lock()

ReplicatedBagOStuff::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 162 of file ReplicatedBagOStuff.php.

◆ merge()

ReplicatedBagOStuff::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 138 of file ReplicatedBagOStuff.php.

◆ set()

ReplicatedBagOStuff::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 102 of file ReplicatedBagOStuff.php.

◆ setMockTime()

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

Reimplemented from BagOStuff.

Definition at line 264 of file ReplicatedBagOStuff.php.

◆ setMulti()

ReplicatedBagOStuff::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 216 of file ReplicatedBagOStuff.php.

◆ unlock()

ReplicatedBagOStuff::unlock (   $key)

Release an advisory lock on a key string.

Parameters
string$key
Returns
bool Success

Reimplemented from BagOStuff.

Definition at line 172 of file ReplicatedBagOStuff.php.


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