class Redis::HashRing

Constants

POINTS_PER_SERVER

Attributes

nodes[R]
replicas[R]
ring[R]
sorted_keys[R]

Public Class Methods

new(nodes = [], replicas = POINTS_PER_SERVER) click to toggle source

nodes is a list of objects that have a proper to_s representation. replicas indicates how many virtual points should be used pr. node, replicas are required to improve the distribution.

# File lib/redis/hash_ring.rb, line 15
def initialize(nodes = [], replicas = POINTS_PER_SERVER)
  @replicas = replicas
  @ring = {}
  @nodes = []
  @sorted_keys = []
  nodes.each do |node|
    add_node(node)
  end
end

Public Instance Methods

add_node(node) click to toggle source

Adds a ‘node` to the hash ring (including a number of replicas).

# File lib/redis/hash_ring.rb, line 26
def add_node(node)
  @nodes << node
  @replicas.times do |i|
    key = server_hash_for("#{node.id}:#{i}")
    @ring[key] = node
    @sorted_keys << key
  end
  @sorted_keys.sort!
end
get_node(key) click to toggle source

get the node in the hash ring for this key

# File lib/redis/hash_ring.rb, line 46
def get_node(key)
  hash = hash_for(key)
  idx = binary_search(@sorted_keys, hash)
  @ring[@sorted_keys[idx]]
end
iter_nodes(key) { |ring[sorted_keys| ... } click to toggle source
# File lib/redis/hash_ring.rb, line 52
def iter_nodes(key)
  return [nil, nil] if @ring.empty?

  crc = hash_for(key)
  pos = binary_search(@sorted_keys, crc)
  @ring.size.times do |n|
    yield @ring[@sorted_keys[(pos + n) % @ring.size]]
  end
end
remove_node(node) click to toggle source
# File lib/redis/hash_ring.rb, line 36
def remove_node(node)
  @nodes.reject! { |n| n.id == node.id }
  @replicas.times do |i|
    key = server_hash_for("#{node.id}:#{i}")
    @ring.delete(key)
    @sorted_keys.reject! { |k| k == key }
  end
end

Private Instance Methods

hash_for(key) click to toggle source
# File lib/redis/hash_ring.rb, line 64
def hash_for(key)
  Zlib.crc32(key)
end
server_hash_for(key) click to toggle source
# File lib/redis/hash_ring.rb, line 68
def server_hash_for(key)
  Digest::MD5.digest(key).unpack1("L>")
end