Class: CHash

Clusterluck.CHash(rfactor, pfactor, treeopt, optsopt)

CHash CHash

Constructor

new CHash(rfactor, pfactor, treeopt, optsopt)

Consistent hash implementation. Maintains a red-black tree containing the hash ring (for ordering), with keys as hashes of node names and values as the nodes themselves. This implementation also contains an rfactor (replication factor) and pfactor (persistence factor). rfactor dictates how many times an element is inserted into the ring, while pfactor dictates how many nodes will be used for redundancy.

Parameters:
Name Type Attributes Description
rfactor Number

Replication factor for node insertion.
pfactor Number

Persistence factor for redundancy in node-neighbor calculations.
tree RBTree <optional>

Existing red-black tree to instantiate local tree from.
opts Object <optional>

Options object for hash ring.

Properties
Name Type Attributes Description
maxCacheSize Number <optional>

Maximum cache size for caching hash values in hash ring. Defaults to 5000.
Source:

Methods

begin() → {Iterator}

Generates an iterator on this hash ring, starting at the first (smallest hash) node.

Source:
Returns:

Iterator over this instance.

Type
Iterator

end() → {Iterator}

Generates an iterator on this hash ring, starting at the last (largest hash) node.

Source:
Returns:

Iterator over this instance.

Type
Iterator

equals(chash) → {Boolean}

Returns whether two consistent hash rings are equal. This involves checking the following:

  • The hash rings have the same size
  • For every entry in this instance's RBT, the corresponding entry exists in the RBT of chash
Parameters:
Name Type Description
chash Clusterluck.CHash

CHash to derive equality against.
Source:
Returns:

Whether this chash instance equals chash.

Type
Boolean

find(data) → {Node}

Finds the next node in the hash ring based on the bucket placement of data. If no succeeding node exists, loops around to the beginning of the hash ring and picks the first node.

Parameters:
Name Type Description
data String

Data to find the next node off of.
Source:
Returns:

Next node in the hash ring.

Type
Node

fromJSON(ent) → {Clusterluck.CHash}

Instantiates state from a JSON object.

Parameters:
Name Type Description
ent Object

JSON object to instantiate state from.
Source:
Returns:

This instance.

Type
Clusterluck.CHash

get(node, def) → {Node}

Gets node from the hash ring by class. Useful if the id is known but host and port need to be queried.

Parameters:
Name Type Description
node Node

Node to access.
def Node

Default value to return if node doesn't exist in the hash ring.
Source:
Returns:

Node with matching id.

Type
Node

insert(node, weightopt) → {Clusterluck.CHash}

Inserts node into this ring, repeating this process rfactor number of times. Ignores insertions if node is already present in the hash ring.

Parameters:
Name Type Attributes Description
node Node

Node to insert into this instance.
weight Number <optional>

Number of times to insert this node. Defaults to rfactor.
Source:
Returns:

This instance.

Type
Clusterluck.CHash

intersect(chash) → {Clusterluck.CHash}

Computes a set-intersection on two hash rings, removing any nodes not found in both rings.

Parameters:
Name Type Description
chash Clusterluck.CHash

Hash ring to intersect with.
Source:
Returns:

This instance.

Type
Clusterluck.CHash

isDefined() → {Boolean}

Checks node is defined in this hash ring.

Source:
Returns:

Whether node is defined.

Type
Boolean

iterator(node) → {Iterator}

Generates an iterator on this hash ring, starting at node.

Parameters:
Name Type Description
node Node

Node to start iteration on.
Source:
Returns:

Iterator over this instance.

Type
Iterator

merge(chash) → {Clusterluck.CHash}

Computes a set-union on two hash rings, inserting any nodes present in chash that aren't in this hash ring.

Parameters:
Name Type Description
chash Clusterluck.CHash

Hash ring to merge with.
Source:
Returns:

This instance.

Type
Clusterluck.CHash

next(node) → {Array}

Returns a list of neighbors of node in the hash ring. This is bounded by pfactor, which dictates the maximum number of neighbors a node can have (barring size limitations).

Parameters:
Name Type Description
node Node

Node to find neighbors of.
Source:
Returns:

Neighbors of node in the hash ring.

Type
Array

nodes() → {Array}

Acts as a getter for the nodes in this hash ring.

Source:
Returns:

List of nodes in this hash ring.

Type
Array

numberNodes() → {Number}

Returns the number of nodes in the ring.

Source:
Returns:

Number of nodes in this hash ring.

Type
Number

pfactor(popt) → {Number}

Acts as a getter/setter for the pfactor of this hash ring.

Parameters:
Name Type Attributes Description
p Number <optional>

pfactor to set on this ring.
Source:
Returns:

pfactor of this instance.

Type
Number

prev(node) → {Array}

Returns a list of preceding neighbors of node in the hash ring. This is bounded by pfactor, which dictates the maximum number of neighbors a node can have (barring size limitations).

Parameters:
Name Type Description
node Node

Node to find neighbors of.
Source:
Returns:

Neighbors of node in the hash ring.

Type
Array

rangeNext(data, rangeopt) → {Array}

Returns a bucket of nodes including and following the hash slot corresponding to data. This is bounded by range, which dictates the size of the bucket returned).

Parameters:
Name Type Attributes Description
data String

Data to calculate hash of and find following nodes.
range Number <optional>

Number of nodes to return. Defaults to rfactor.
Source:
Returns:

Bucket of nodes with size range associated with key data.

Type
Array

rangePrev(data, rangeopt) → {Array}

Returns a bucket of nodes preceding the hash slot corresponding to data. This is bounded by range, which dictates the size of the bucket returned).

Parameters:
Name Type Attributes Description
data String

Data to calculate hash of and find following nodes.
range Number <optional>

Number of nodes to return. Defaults to rfactor.
Source:
Returns:

Bucket of nodes with size range preceding key data.

Type
Array

remove(node) → {Clusterluck.CHash}

Removes node from this ring, repeating this process rfactor number of times. Ignores removals node doesn't exist in the ring.

Parameters:
Name Type Description
node Node

Node to remove from this instance.
Source:
Returns:

This instance.

Type
Clusterluck.CHash

rfactor(ropt) → {Number}

Acts as a getter/setter for the rfactor of this hash ring.

Parameters:
Name Type Attributes Description
r Number <optional>

rfactor to set on this ring.
Source:
Returns:

rfactor of this instance.

Type
Number

size() → {Number}

Acts as a getter for the number of elements in this hash ring.

Source:
Returns:

Number of elements in this hash ring.

Type
Number

toJSON(fastopt) → {Object}

Computes the JSON serialization of this instance. Useful when periodically flushing this ring to disk.

Parameters:
Name Type Attributes Description
fast Boolean <optional>

Whether to compute the JSON serialization of this instance using a copy of internal state.
Source:
Returns:

JSON serialization of this instance.

Type
Object

tree(treeopt) → {RBTree}

Acts as a getter/setter for the red-black tree of this hash ring.

Parameters:
Name Type Attributes Description
tree RBTree <optional>

Tree to set on this instance.
Source:
Returns:

Red-black tree of this instance.

Type
RBTree

update(node, weight) → {Clusterluck.CHash}

Update the weight of node in the hash ring.

Parameters:
Name Type Description
node Node

Node to add state to.
weight Number

Weight to change node to in the ring.
Source:
Returns:

This instance.

Type
Clusterluck.CHash

weights() → {Map}

Returns the weight map from node IDs to weights in the hash ring.

Source:
Returns:

Weight map from node IDs to weights

Type
Map