Interface to key-value storage behind an HTTP server. More...

Collaboration diagram for RESTBagOStuff:

[legend]

Public Member Functions
	__construct ( $params)

	setLogger (LoggerInterface $logger)

Public Member Functions inherited from MediumSpecificBagOStuff
	__construct (array $params=[])

	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 a key if it exists.

	changeTTLMulti (array $keys, $exptime, $flags=0)
	Change the expiration of multiple keys that exist.

	delete ( $key, $flags=0)
	Delete an item.

	deleteMulti (array $keys, $flags=0)
	Batch deletion.

	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 with the given key.

	getMulti (array $keys, $flags=0)
	Get an associative array containing the item for each of the keys that have items.

	getQoS ( $flag)

	getSegmentationSize ()

	getSegmentedValueMaxSize ()

	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='')

	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.

	setMulti (array $valueByKey, $exptime=0, $flags=0)
	Batch insertion/replace.

	unlock ( $key)
	Release an advisory lock on a key string.

Public Member Functions inherited from BagOStuff
	clearLastError ()
	Clear the "last error" registry.

	getCurrentTime ()

	getLastError ( $watchPoint=0)
	Get the "last error" registry.

	getLogger ()

	getScopedLock ( $key, $timeout=6, $exptime=30, $rclass='')
	Get a lightweight exclusive self-unlocking lock.

	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.

	setMockTime (&$time)

	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.

Protected Member Functions
	doAdd ( $key, $value, $exptime=0, $flags=0)
	Insert an item if it does not already exist.

	doDelete ( $key, $flags=0)
	Delete an item.

	doGet ( $key, $flags=0, &$casToken=null)
	Get an item.

	doIncrWithInit ( $key, $exptime, $step, $init, $flags)

	doSet ( $key, $value, $exptime=0, $flags=0)
	Set an item.

	handleError ( $msg, $rcode, $rerr, $rhdrs, $rbody, $context=[])
	Handle storage error.

Protected Member Functions inherited from MediumSpecificBagOStuff
	cas ( $casToken, $key, $value, $exptime=0, $flags=0)
	Set an item if the current CAS token matches the provided CAS token.

	debug ( $text)

	doCas ( $casToken, $key, $value, $exptime=0, $flags=0)
	Set an item if the current CAS token matches the provided CAS token.

	doChangeTTL ( $key, $exptime, $flags)

	doChangeTTLMulti (array $keys, $exptime, $flags=0)

	doDeleteMulti (array $keys, $flags=0)

	doGetMulti (array $keys, $flags=0)
	Get an associative array containing the item for each of the keys that have items.

	doLock ( $key, $timeout, $exptime)

	doSetMulti (array $data, $exptime=0, $flags=0)

	doUnlock ( $key)

	getExpirationAsTimestamp ( $exptime)
	Convert an optionally relative timestamp to an absolute time.

	getExpirationAsTTL ( $exptime)
	Convert an optionally absolute expiry time to a relative time.

	getSerialized ( $value, $key)
	Get the serialized form a value, logging a warning if it involves custom classes.

	isInteger ( $value)
	Check if a value is an integer.

	isRelativeExpiration ( $exptime)

	makeLockKey ( $key)

	makeValueOrSegmentList ( $key, $value, $exptime, $flags, &$ok)
	Make the entry to store at a key (inline or segment list), storing any segments.

	mergeViaCas ( $key, callable $callback, $exptime, $attempts, $flags)

	resolveSegments ( $key, $mainValue)
	Get and reassemble the chunks of blob at the given key.

	serialize ( $value)

	tokensMatch ( $value, $otherValue)

	unserialize ( $value)

	updateOpStats (string $op, array $keyInfo)

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.

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 Attributes inherited from MediumSpecificBagOStuff
array< string, array >	$locks = []
	Map of (key => (class LOCK_* constant => value)

float	$maxLockSendDelay = 0.05
	Seconds; maximum expected seconds for a lock ping to reach the backend.

int	$segmentationSize
	Bytes; chunk size of segmented cache values.

int	$segmentedValueMaxSize
	Bytes; maximum total size of a segmented cache value.

const	LOCK_DEPTH = 1

const	LOCK_EXPIRY = 3

const	LOCK_RCLASS = 0

const	LOCK_TIME = 2

const	METRIC_OP_ADD = 'add'

const	METRIC_OP_CAS = 'cas'

const	METRIC_OP_CHANGE_TTL = 'change_ttl'

const	METRIC_OP_DECR = 'decr'

const	METRIC_OP_DELETE = 'delete'

const	METRIC_OP_GET = 'get'

const	METRIC_OP_INCR = 'incr'

const	METRIC_OP_SET = 'set'

const	PASS_BY_REF = -1
	Idiom for doGet() to return extra information by reference.

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

Interface to key-value storage behind an HTTP server.

Important caveats

This interface is currently an incomplete BagOStuff implementation, supported only for use with MediaWiki features that accept a dedicated cache type to use for a narrow set of cache keys that share the same key expiry and replication requirements, and where the key-value server in question is statically configured with domain knowledge of said key expiry and replication requirements.

Specifically, RESTBagOStuff has the following limitations:

The expiry parameter is ignored in methods like set().

There is not currently an agreed protocol for sending this to a server. This class is written for use with MediaWiki\Session\SessionManager and Kask/Cassanda at WMF, which does not expose a customizable expiry.

As such, it is not recommended to use RESTBagOStuff to back a general purpose cache type (such as MediaWiki's main cache, or main stash). Instead, it is only supported toMediaWiki features where a cache type can be pointed for a narrow set of keys that naturally share the same TTL anyway, or where the feature behaves correctly even if the logical expiry is longer than specified (e.g. immutable keys, or value verification)
Most methods are non-atomic.

The class should only be used for get, set, and delete operations. Advanced methods like incr(), add() and lock() do exist but inherit a native and best-effort implementation based on get+set. These should not be relied upon.

Backend requirements

The HTTP server will receive requests for URLs like {baseURL}/{KEY}. It must implement the GET, PUT and DELETE methods.

E.g., when the base URL is /sessions/v1, then set() will:

PUT /sessions/v1/mykeyhere

and get() would do:

GET /sessions/v1/mykeyhere

and delete() would do:

DELETE /sessions/v1/mykeyhere

Example configuration

Minimal generic configuration:

$wgObjectCaches['sessions'] = array(
 'class' => 'RESTBagOStuff',
 'url' => 'http://localhost:7231/example/'
);

Configuration for Kask session store:

$wgObjectCaches['sessions'] = array(
 'class' => 'RESTBagOStuff',
 'url' => 'https://kaskhost:1234/sessions/v1/',
 'httpParams' => [
    'readHeaders' => [],
    'writeHeaders' => [ 'content-type' => 'application/octet-stream' ],
    'deleteHeaders' => [],
    'writeMethod' => 'POST',
 ],
 'serialization_type' => 'JSON',
    'extendedErrorBodyFields' => [ 'type', 'title', 'detail', 'instance' ]
);
$wgSessionCacheType = 'sessions';

Definition at line 85 of file RESTBagOStuff.php.

Constructor & Destructor Documentation

◆ __construct()

RESTBagOStuff::__construct ( $params )

Definition at line 132 of file RESTBagOStuff.php.

References Wikimedia\LightweightObjectStore\StorageAwareness\ATTR_DURABILITY, and Wikimedia\LightweightObjectStore\StorageAwareness\QOS_DURABILITY_DISK.

Member Function Documentation

◆ doAdd()

RESTBagOStuff::doAdd	(	$key,
		$value,
		$exptime = 0,
		$flags = 0 )

protected

Insert an item if it does not already exist.

Parameters

string	$key
mixed	$value
int	$exptime
int	$flags	Bitfield of BagOStuff::WRITE_* constants (since 1.33)

Returns: bool Success

Reimplemented from MediumSpecificBagOStuff.

Definition at line 226 of file RESTBagOStuff.php.

◆ doDelete()

RESTBagOStuff::doDelete	(		$key,
			$flags = 0 )

protected

Delete an item.

Parameters

string	$key
int	$flags	Bitfield of BagOStuff::WRITE_* constants

Returns: bool True if the item was deleted or not found, false on failure

Reimplemented from MediumSpecificBagOStuff.

Definition at line 236 of file RESTBagOStuff.php.

References handleError(), and MediumSpecificBagOStuff\updateOpStats().

◆ doGet()

RESTBagOStuff::doGet	(		$key,
			$flags = 0,
		&	$casToken = null )

protected

Get an item.

The CAS token should be null if the key does not exist or the value is corrupt

Parameters

string	$key
int	$flags	Bitfield of BagOStuff::READ_* constants [optional]
mixed	&$casToken	CAS token if MediumSpecificBagOStuff::PASS_BY_REF [returned]

Returns: mixed Returns false on failure or if the item does not exist

Reimplemented from MediumSpecificBagOStuff.

Definition at line 176 of file RESTBagOStuff.php.

References handleError(), MediumSpecificBagOStuff\PASS_BY_REF, and MediumSpecificBagOStuff\updateOpStats().

Referenced by doIncrWithInit().

◆ doIncrWithInit()

RESTBagOStuff::doIncrWithInit	(	$key,
		$exptime,
		$step,
		$init,
		$flags )

protected

Parameters

string	$key
int	$exptime
int	$step
int	$init
int	$flags

Returns: int|bool New value or false on failure

Reimplemented from MediumSpecificBagOStuff.

Definition at line 255 of file RESTBagOStuff.php.

References doGet(), doSet(), and MediumSpecificBagOStuff\isInteger().

◆ doSet()

RESTBagOStuff::doSet	(	$key,
		$value,
		$exptime = 0,
		$flags = 0 )

protected

Set an item.

Parameters

string	$key
mixed	$value
int	$exptime	Either an interval in seconds or a unix timestamp for expiry
int	$flags	Bitfield of BagOStuff::WRITE_* constants

Returns: bool Success

Reimplemented from MediumSpecificBagOStuff.

Definition at line 206 of file RESTBagOStuff.php.

References handleError(), and MediumSpecificBagOStuff\updateOpStats().

Referenced by doIncrWithInit().

◆ handleError()

RESTBagOStuff::handleError	(	$msg,
		$rcode,
		$rerr,
		$rhdrs,
		$rbody,
		$context = [] )

protected

Handle storage error.

Parameters

string	$msg	Error message
int	$rcode	Error code from client
string	$rerr	Error message from client
array	$rhdrs	Response headers
string	$rbody	Error body from client (if any)
array	$context	Error context for PSR-3 logging

Definition at line 350 of file RESTBagOStuff.php.

References Wikimedia\LightweightObjectStore\StorageAwareness\ERR_UNEXPECTED, and BagOStuff\setLastError().

Referenced by doDelete(), doGet(), and doSet().

◆ setLogger()

RESTBagOStuff::setLogger ( LoggerInterface $logger )

Parameters

LoggerInterface $logger

Returns: void

Reimplemented from BagOStuff.

Definition at line 171 of file RESTBagOStuff.php.

References BagOStuff\$logger.

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

includes/libs/objectcache/RESTBagOStuff.php

Public Member Functions

Protected Member Functions

Additional Inherited Members

Detailed Description

Important caveats

Backend requirements

Example configuration

Constructor & Destructor Documentation

◆ __construct()

Member Function Documentation

◆ doAdd()

◆ doDelete()

◆ doGet()

◆ doIncrWithInit()

◆ doSet()

◆ handleError()

◆ setLogger()