first commit

client-libraries/ruby/lib/hash_ring.rb

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+require 'digest/md5'
+class HashRing
+  attr_reader :ring, :sorted_keys, :replicas, :nodes
+  # 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.
+  def initialize(nodes=[], replicas=3)
+    @replicas = replicas
+    @ring = {}
+    @nodes = []
+    @sorted_keys = []
+    nodes.each do |node|
+      add_node(node)
+    end
+  end
+  
+  # Adds a `node` to the hash ring (including a number of replicas).
+  def add_node(node)
+    @nodes << node
+    @replicas.times do |i|
+      key = gen_key("#{node}:#{i}")
+      @ring[key] = node
+      @sorted_keys << key
+    end
+    @sorted_keys.sort!
+  end
+  
+  def remove_node(node)
+    @replicas.times do |i|
+      key = gen_key("#{node}:#{count}")
+      @ring.delete(key)
+      @sorted_keys.reject! {|k| k == key}
+    end
+  end
+  
+  # get the node in the hash ring for this key
+  def get_node(key)
+    get_node_pos(key)[0]
+  end
+  
+  def get_node_pos(key)
+    return [nil,nil] if @ring.size == 0
+    key = gen_key(key)
+    nodes = @sorted_keys
+    nodes.size.times do |i|
+      node = nodes[i]
+      if key <= node
+        return [@ring[node], i]
+      end
+    end
+    [@ring[nodes[0]], 0]
+  end
+  
+  def iter_nodes(key)
+    return [nil,nil] if @ring.size == 0
+    node, pos = get_node_pos(key)
+    @sorted_keys[pos..-1].each do |k|
+      yield @ring[k]
+    end  
+  end
+  
+  def gen_key(key)
+    key = Digest::MD5.hexdigest(key)
+    ((key[3] << 24) | (key[2] << 16) | (key[1] << 8) | key[0])
+  end
+  
+end
+
+# ring = HashRing.new ['server1', 'server2', 'server3']
+# p ring
+# #
+# p ring.get_node "kjhjkjlkjlkkh"
+#