Add the :nearest mode, which selects the closest node by ping, regardless of role

Author: cheald

lib/redis/client.rb

@@ -484,7 +484,8 @@ def check(client)
 
       class Sentinel < Connector
         EXPECTED_ROLES = {
-          "nearest_slave" => "slave"
+          "nearest_slave" => "slave",
+          "nearest" => "any"
         }
 
         def initialize(options)
@@ -502,14 +503,15 @@ def check(client)
           # Check the instance is really of the role we are looking for.
           # We can't assume the command is supported since it was introduced
           # recently and this client should work with old stuff.
+          expected_role = EXPECTED_ROLES.fetch(@role, @role)
           begin
             role = client.call([:role])[0]
           rescue Redis::CommandError
             # Assume the test is passed if we can't get a reply from ROLE...
-            role = EXPECTED_ROLES.fetch(@role, @role)
+            role = expected_role
           end
 
-          if role != EXPECTED_ROLES.fetch(@role, @role)
+          if role != expected_role && "any" != expected_role
             client.disconnect
             raise ConnectionError, "Instance role mismatch. Expected #{EXPECTED_ROLES.fetch(@role, @role)}, got #{role}."
           end
@@ -521,6 +523,8 @@ def resolve
                      resolve_master
                    when "slave"
                      resolve_slave
+                   when "nearest"
+                     resolve_nearest
                    when "nearest_slave"
                      resolve_nearest_slave
                    else
@@ -573,30 +577,49 @@ def resolve_slave
           end
         end
 
+        def resolve_nearest
+          resolve_nearest_for [:master, :slaves]
+        end
+
         def resolve_nearest_slave
+          resolve_nearest_for [:slaves]
+        end
+
+        def resolve_nearest_for(types)
           sentinel_detect do |client|
-            if reply = client.call(["sentinel", "slaves", @master])
-              ok_slaves = reply.map {|r| Hash[*r] }.select  {|r| r["master-link-status"] == "ok" }
-
-              ok_slaves.each do |slave|
-                client = Client.new @options.merge(
-                  :host => slave["ip"],
-                  :port => slave["port"],
-                  :reconnect_attempts => 0
-                )
-                begin
-                  client.call [:ping]
-                  start = Time.now
-                  client.call [:ping]
-                  slave["response_time"] = (Time.now - start).to_f
-                ensure
-                  client.disconnect
+            ok_nodes = []
+            types.each do |type|
+              if reply = client.call(["sentinel", type, @master])
+                reply = [reply] if type == :master
+                ok_nodes += reply.map {|r| Hash[*r] }.select do |r|
+                  case type
+                  when :master
+                    r["role-reported"] == "master"
+                  when :slaves
+                    r["master-link-status"] == "ok" && !r.fetch("flags", "").match(/s_down|disconnected/)
+                  end
                 end
               end
+            end
 
-              slave = ok_slaves.sort_by {|slave| slave["response_time"] }.first
-              {:host => slave.fetch("ip"), :port => slave.fetch("port")} if slave
+            ok_nodes.each do |node|
+              client = Client.new @options.merge(
+                :host => node["ip"],
+                :port => node["port"],
+                :reconnect_attempts => 0
+              )
+              begin
+                client.call [:ping]
+                start = Time.now
+                client.call [:ping]
+                node["response_time"] = (Time.now - start).to_f
+              ensure
+                client.disconnect
+              end
             end
+
+            node = ok_nodes.sort_by {|node| node["response_time"] }.first
+            {:host => node.fetch("ip"), :port => node.fetch("port")} if node
           end
         end
 

test/sentinel_test.rb

@@ -253,13 +253,58 @@ def test_sentinel_retries
     assert_match(/No sentinels available/, ex.message)
   end
 
+  def test_sentinel_nearest
+    sentinels = [{:host => "127.0.0.1", :port => 26381}]
+
+    master = { :role => lambda { ["master"] }, :node_id => lambda { ["master"] }, :ping => lambda { ["OK"] } }
+    s1     = { :role => lambda { ["slave"] }, :node_id => lambda { ["1"] }, :ping => lambda { sleep 0.1; ["OK"] } }
+    s2     = { :role => lambda { ["slave"] }, :node_id => lambda { ["2"] }, :ping => lambda { sleep 0.2; ["OK"] } }
+    s3     = { :role => lambda { ["slave"] }, :node_id => lambda { ["3"] }, :ping => lambda { sleep 0.3; ["OK"] } }
+
+    5.times do
+      RedisMock.start(master) do |master_port|
+        RedisMock.start(s1) do |s1_port|
+          RedisMock.start(s2) do |s2_port|
+            RedisMock.start(s3) do |s3_port|
+
+              sentinel = lambda do |port|
+                {
+                  :sentinel => lambda do |command, *args|
+                    case command
+                    when "master"
+                      %W[role-reported master ip 127.0.0.1 port #{master_port}]
+                    when "slaves"
+                      [
+                        %W[master-link-status down ip 127.0.0.1 port #{s1_port}],
+                        %W[master-link-status ok ip 127.0.0.1 port #{s2_port}],
+                        %W[master-link-status ok ip 127.0.0.1 port #{s3_port}]
+                      ].shuffle
+                    else
+                      ["127.0.0.1", port.to_s]
+                    end
+                  end
+                }
+              end
+
+              RedisMock.start(sentinel.call(master_port)) do |sen_port|
+                sentinels[0][:port] = sen_port
+                redis = Redis.new(:url => "redis://master1", :sentinels => sentinels, :role => :nearest)
+                assert_equal ["master"], redis.node_id
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+
   def test_sentinel_nearest_slave
     sentinels = [{:host => "127.0.0.1", :port => 26381}]
 
     master = { :role => lambda { ["master"] } }
-    s1 = { :role => lambda { ["slave"] }, :slave_id => lambda { ["1"] }, :ping => lambda { ["OK"] } }
-    s2 = { :role => lambda { ["slave"] }, :slave_id => lambda { ["2"] }, :ping => lambda { sleep 0.1; ["OK"] } }
-    s3 = { :role => lambda { ["slave"] }, :slave_id => lambda { ["3"] }, :ping => lambda { sleep 0.2; ["OK"] } }
+    s1 = { :role => lambda { ["slave"] }, :node_id => lambda { ["1"] }, :ping => lambda { ["OK"] } }
+    s2 = { :role => lambda { ["slave"] }, :node_id => lambda { ["2"] }, :ping => lambda { sleep 0.1; ["OK"] } }
+    s3 = { :role => lambda { ["slave"] }, :node_id => lambda { ["3"] }, :ping => lambda { sleep 0.2; ["OK"] } }
 
     5.times do
       RedisMock.start(master) do |master_port|
@@ -287,7 +332,7 @@ def test_sentinel_nearest_slave
               RedisMock.start(sentinel.call(master_port)) do |sen_port|
                 sentinels[0][:port] = sen_port
                 redis = Redis.new(:url => "redis://master1", :sentinels => sentinels, :role => :nearest_slave)
-                assert_equal redis.slave_id, ["2"]
+                assert_equal redis.node_id, ["2"]
               end
             end
           end