Merge pull request #1124 from fatkodima/optimize-node_for

Optimize getting server for key in Redis::Distributed

Author: byroot

lib/redis/distributed.rb

@@ -1004,7 +1004,8 @@ def node_index_for(key)
     end
 
     def key_tag(key)
-      key.to_s[@tag, 1] if @tag
+      key = key.to_s
+      key[@tag, 1] if key.match?(@tag)
     end
 
     def ensure_same_node(command, keys)

lib/redis/hash_ring.rb

@@ -44,49 +44,21 @@ def remove_node(node)
 
     # 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.empty?
-
       hash = hash_for(key)
-      idx = HashRing.binary_search(@sorted_keys, hash)
-      [@ring[@sorted_keys[idx]], idx]
+      idx = binary_search(@sorted_keys, hash)
+      @ring[@sorted_keys[idx]]
     end
 
     def iter_nodes(key)
       return [nil, nil] if @ring.empty?
 
-      _, pos = get_node_pos(key)
+      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
 
-    # Find the closest index in HashRing with value <= the given value
-    def self.binary_search(ary, value)
-      upper = ary.size - 1
-      lower = 0
-      idx = 0
-
-      while lower <= upper
-        idx = (lower + upper) / 2
-        comp = ary[idx] <=> value
-
-        if comp == 0
-          return idx
-        elsif comp > 0
-          upper = idx - 1
-        else
-          lower = idx + 1
-        end
-      end
-
-      upper = ary.size - 1 if upper < 0
-      upper
-    end
-
     private
 
     def hash_for(key)
@@ -96,5 +68,22 @@ def hash_for(key)
     def server_hash_for(key)
       Digest::MD5.digest(key).unpack1("L>")
     end
+
+    # Find the closest index in HashRing with value <= the given value
+    def binary_search(ary, value)
+      upper = ary.size
+      lower = 0
+
+      while lower < upper
+        mid = (lower + upper) / 2
+        if ary[mid] > value
+          upper = mid
+        else
+          lower = mid + 1
+        end
+      end
+
+      upper - 1
+    end
   end
 end