Convenience class for weighted consistent hash rings. More...

Inheritance diagram for HashRing:

Collaboration diagram for HashRing:

Public Member Functions
	__construct (array $map, $algo='sha1', array $ejections=[])
	Make a consistent hash ring given a set of locations and their weight values.

	__serialize ()

	__unserialize ( $data)

	ejectFromLiveRing ( $location, $ttl)
	Remove a location from the "live" hash ring.

	getLiveLocation ( $item)
	Get the location of an item on the "live" ring.

	getLiveLocations ( $item, $limit)
	Get the location of an item on the "live" ring, as well as the next locations.

	getLiveLocationWeights ()
	Get the map of "live" locations to weight (does not include zero weight items)

	getLocation ( $item)
	Get the location of an item on the ring.

	getLocations ( $item, $limit, $from=self::RING_ALL)
	Get the location of an item on the ring followed by the next ring locations.

	getLocationWeights ()
	Get the map of locations to weight (does not include zero weight items)

	serialize ()

	unserialize ( $serialized)

Public Attributes
const	KEY_LOCATION = 1

const	KEY_POS = 0

Protected Member Functions
	getCurrentTime ()

	getLiveRing ()
	Get the "live" hash ring (which does not include ejected locations)

	init (array $map, $algo, array $ejections)

Protected Attributes
string	$algo
	Hashing algorithm for hash()

array[]	$baseRing
	Non-empty position-ordered list of (position, location name)

int[]	$ejectExpiryByLocation
	Map of (location => UNIX timestamp)

array[]	$liveRing
	Non-empty position-ordered list of (position, location name)

int[]	$weightByLocation
	Non-empty (location => integer weight)

Private Member Functions
	buildLocationRing (array $weightByLocation)

	findNodeIndexForPosition ( $position, $ring)

	getItemPosition ( $item)

	getNextClockwiseNodeIndex ( $i, $ring)

	getNodePositionQuartet ( $nodeGroupName)

Detailed Description

Convenience class for weighted consistent hash rings.

This deterministically maps "keys" to a set of "locations" while avoiding clumping

Each location is represented by a number of nodes on a ring proportionate to the ratio of its weight compared to the total location weight. Note positions are deterministically derived from the hash of the location name. Nodes are responsible for the portion of the ring, counter-clockwise, up until the next node. Locations are responsible for all portions of the ring that the location's nodes are responsible for.

A location that is temporarily "ejected" is said to be absent from the "live" ring. If no location ejections are active, then the base ring and live ring are identical.

This class is designed in a way that using the "md5" algorithm will make it compatible with libketama, e.g. OPT_LIBKETAMA_COMPATIBLE from the PECL memcached extension or "ketama" from twemproxy. This can simplify the process of switching client libraries. However, note that different clients might use incompatible 32-bit memcached value flag conventions.

Since: 1.22

Definition at line 44 of file HashRing.php.

Constructor & Destructor Documentation

◆ __construct()

HashRing::__construct	(	array	$map,
			$algo = `'sha1'`,
		array	$ejections = `[]`
	)

Make a consistent hash ring given a set of locations and their weight values.

Parameters

int[]	$map	Map of (location => weight)
string	$algo	Hashing algorithm listed in hash_algos() [optional]
int[]	$ejections	Map of (location => UNIX timestamp) for ejection expiries

Since: 1.31

Definition at line 78 of file HashRing.php.

References $algo, and init().

Member Function Documentation

◆ __serialize()

HashRing::__serialize ( )

Definition at line 444 of file HashRing.php.

◆ __unserialize()

HashRing::__unserialize ( $data )

Definition at line 456 of file HashRing.php.

◆ buildLocationRing()

HashRing::buildLocationRing ( array $weightByLocation )

private

Parameters

int[] $weightByLocation

Returns: array[]

Definition at line 285 of file HashRing.php.

References $weightByLocation, and getNodePositionQuartet().

Referenced by init().

◆ ejectFromLiveRing()

HashRing::ejectFromLiveRing	(	$location,
		$ttl
	)

Remove a location from the "live" hash ring.

Parameters

string	$location
int	$ttl	Seconds

Returns: bool Whether some non-ejected locations are left

Exceptions

UnexpectedValueException

Definition at line 225 of file HashRing.php.

References getCurrentTime().

Referenced by JobQueueFederated\tryJobInsertions().

◆ findNodeIndexForPosition()

HashRing::findNodeIndexForPosition	(	$position,
		$ring
	)

private

Parameters

float	$position
array[]	$ring	Either the base or live ring

Returns: int|null

Definition at line 170 of file HashRing.php.

References KEY_POS.

Referenced by getLocations().

◆ getCurrentTime()

HashRing::getCurrentTime ( )

protected

Returns: int UNIX timestamp

Definition at line 436 of file HashRing.php.

Referenced by ejectFromLiveRing(), getLiveLocationWeights(), and getLiveRing().

◆ getItemPosition()

HashRing::getItemPosition ( $item )

private

Parameters

string $item Key

Returns: float Ring position; integral number in [0, 4294967296] (2^32)

Definition at line 337 of file HashRing.php.

Referenced by getLocations().

◆ getLiveLocation()

HashRing::getLiveLocation ( $item )

final

Get the location of an item on the "live" ring.

Parameters

string $item

Returns: string Location

Exceptions

UnexpectedValueException

Definition at line 245 of file HashRing.php.

References getLocations().

Referenced by JobQueueFederated\tryJobInsertions().

◆ getLiveLocations()

HashRing::getLiveLocations	(	$item,
		$limit
	)

final

Get the location of an item on the "live" ring, as well as the next locations.

Parameters

string	$item
int	$limit	Maximum number of locations to return

Returns: string[] List of locations

Exceptions

UnexpectedValueException

Definition at line 257 of file HashRing.php.

References getLocations().

◆ getLiveLocationWeights()

HashRing::getLiveLocationWeights ( )

Get the map of "live" locations to weight (does not include zero weight items)

Returns: int[]

Exceptions

UnexpectedValueException

Definition at line 267 of file HashRing.php.

References getCurrentTime().

Referenced by JobQueueFederated\doBatchPush(), and JobQueueFederated\tryJobInsertions().

◆ getLiveRing()

HashRing::getLiveRing ( )

protected

Get the "live" hash ring (which does not include ejected locations)

Returns: array[]

Exceptions

UnexpectedValueException

Definition at line 394 of file HashRing.php.

References $baseRing, $liveRing, getCurrentTime(), and KEY_LOCATION.

Referenced by getLocations().

◆ getLocation()

HashRing::getLocation ( $item )

final

Get the location of an item on the ring.

Parameters

string $item

Returns: string Location

Exceptions

UnexpectedValueException

Definition at line 112 of file HashRing.php.

References getLocations().

◆ getLocations()

HashRing::getLocations	(	$item,
		$limit,
		$from = `self::RING_ALL`
	)

Get the location of an item on the ring followed by the next ring locations.

Parameters

string	$item
int	$limit	Maximum number of locations to return
int	$from	One of the RING_* class constants

Returns: string[] List of locations

Exceptions

InvalidArgumentException
UnexpectedValueException

Definition at line 126 of file HashRing.php.

References $baseRing, findNodeIndexForPosition(), getItemPosition(), getLiveRing(), getNextClockwiseNodeIndex(), and KEY_LOCATION.

Referenced by getLiveLocation(), getLiveLocations(), and getLocation().

◆ getLocationWeights()

HashRing::getLocationWeights ( )

Get the map of locations to weight (does not include zero weight items)

Returns: int[]

Definition at line 213 of file HashRing.php.

References $weightByLocation.

◆ getNextClockwiseNodeIndex()

HashRing::getNextClockwiseNodeIndex	(	$i,
		$ring
	)

private

Parameters

int	$i	Valid index for a node in the ring
array[]	$ring	Either the base or live ring

Returns: int Valid index for a node in the ring

Definition at line 378 of file HashRing.php.

Referenced by getLocations().

◆ getNodePositionQuartet()

HashRing::getNodePositionQuartet ( $nodeGroupName )

private

Parameters

string $nodeGroupName

Returns: float[] Four ring positions on [0, 4294967296] (2^32)

Definition at line 359 of file HashRing.php.

Referenced by buildLocationRing().

◆ init()

HashRing::init	(	array	$map,
			$algo,
		array	$ejections
	)

protected

Parameters

int[]	$map	Map of (location => integer)
string	$algo	Hashing algorithm
int[]	$ejections	Map of (location => UNIX timestamp) for ejection expires

Definition at line 87 of file HashRing.php.

References $algo, $weightByLocation, and buildLocationRing().

Referenced by __construct().

◆ serialize()

HashRing::serialize ( )

Definition at line 440 of file HashRing.php.

◆ unserialize()

HashRing::unserialize ( $serialized )

Definition at line 452 of file HashRing.php.

Member Data Documentation

◆ $algo

string HashRing::$algo

protected

Hashing algorithm for hash()

Definition at line 46 of file HashRing.php.

Referenced by __construct(), and init().

◆ $baseRing

array [] HashRing::$baseRing

protected

Non-empty position-ordered list of (position, location name)

Definition at line 53 of file HashRing.php.

Referenced by getLiveRing(), and getLocations().

◆ $ejectExpiryByLocation

int [] HashRing::$ejectExpiryByLocation

protected

Map of (location => UNIX timestamp)

Definition at line 50 of file HashRing.php.

◆ $liveRing

array [] HashRing::$liveRing

protected

Non-empty position-ordered list of (position, location name)

Definition at line 55 of file HashRing.php.

Referenced by getLiveRing().

◆ $weightByLocation

int [] HashRing::$weightByLocation

protected

Non-empty (location => integer weight)

Definition at line 48 of file HashRing.php.

Referenced by buildLocationRing(), getLocationWeights(), and init().

◆ KEY_LOCATION

const HashRing::KEY_LOCATION = 1

Definition at line 63 of file HashRing.php.

Referenced by getLiveRing(), and getLocations().

◆ KEY_POS

const HashRing::KEY_POS = 0

Definition at line 62 of file HashRing.php.

Referenced by findNodeIndexForPosition().

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

includes/libs/HashRing.php

Public Member Functions

Public Attributes

Protected Member Functions

Protected Attributes

Private Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ __construct()

Member Function Documentation

◆ __serialize()

◆ __unserialize()

◆ buildLocationRing()

◆ ejectFromLiveRing()

◆ findNodeIndexForPosition()

◆ getCurrentTime()

◆ getItemPosition()

◆ getLiveLocation()

◆ getLiveLocations()

◆ getLiveLocationWeights()

◆ getLiveRing()

◆ getLocation()

◆ getLocations()

◆ getLocationWeights()

◆ getNextClockwiseNodeIndex()

◆ getNodePositionQuartet()

◆ init()

◆ serialize()

◆ unserialize()

Member Data Documentation

◆ $algo

◆ $baseRing

◆ $ejectExpiryByLocation

◆ $liveRing

◆ $weightByLocation

◆ KEY_LOCATION

◆ KEY_POS