ensure that only currently visible nodes are candidates for failover

lib/redis_failover/failover_strategy/latency.rb

@@ -5,9 +5,6 @@ class FailoverStrategy
     class Latency < FailoverStrategy
       # @see RedisFailover::FailoverStrategy#find_candidate
       def find_candidate(snapshots)
-        logger.info('Attempting to find candidate from snapshots:')
-        logger.info("\n" + snapshots.values.join("\n"))
-
         candidates = {}
         snapshots.each do |node, snapshot|
           if snapshot.all_available?

lib/redis_failover/node_manager.rb

@@ -195,7 +195,7 @@ def promote_new_master(snapshots, node = nil)
       @master = nil
 
       # make a specific node or selected candidate the new master
-      candidate = node || @failover_strategy.find_candidate(snapshots)
+      candidate = node || failover_strategy_candidate(snapshots)
 
       unless candidate
         logger.error('Failed to promote a new master, no candidate available.')
@@ -627,7 +627,7 @@ def perform_manual_failover
         snapshots = current_node_snapshots
 
         node = if new_master == ManualFailover::ANY_SLAVE
-          @failover_strategy.find_candidate(snapshots)
+          failover_strategy_candidate(snapshots)
         else
           node_from(new_master)
         end
@@ -672,11 +672,26 @@ def ensure_sufficient_node_managers(snapshots)
       end
 
       if currently_sufficient && !@sufficient_node_managers
-        logger.info("Can see all required Node Managers: #{@required_node_managers}")
+        logger.info("Required Node Managers are visible: #{@required_node_managers}")
       end
 
       @sufficient_node_managers = currently_sufficient
       @sufficient_node_managers
     end
+
+    # Invokes the configured failover strategy.
+    #
+    # @param [Hash<Node, NodeSnapshot>] snapshots the node snapshots
+    # @return [Node] a failover candidate
+    def failover_strategy_candidate(snapshots)
+      # only include nodes that this master Node Manager can see
+      filtered_snapshots = snapshots.select do |node, snapshot|
+        snapshot.viewable_by?(manager_id)
+      end
+
+      logger.info('Attempting to find candidate from snapshots:')
+      logger.info("\n" + filtered_snapshots.values.join("\n"))
+      @failover_strategy.find_candidate(filtered_snapshots)
+    end
   end
 end

lib/redis_failover/node_snapshot.rb

@@ -17,15 +17,22 @@ def initialize(node)
 
     # Declares this node available by the specified node manager.
     #
-    # @param [String] node_manager the znode path for the node manager
+    # @param [String] node_manager the node manager id
     # @param [Integer] latency the latency
     def viewable_by(node_manager, latency)
       @available[node_manager] = latency
     end
 
+    # Determines if this node is viewable by a node manager.
+    #
+    # @param [String] node_manager the node manager id
+    def viewable_by?(node_manager)
+      @available.key?(node_manager)
+    end
+
     # Declares this node unavailable by the specified node manager.
     #
-    # @param [String] node_manager the znode path for the node manager
+    # @param [String] node_manager the node manager id
     def unviewable_by(node_manager)
       @unavailable << node_manager
     end

spec/support/node_manager_stub.rb

@@ -18,10 +18,6 @@ def discover_nodes
       @master = master
       @slaves = [slave]
       @failover_strategy = Object.new
-      slaves = @slaves
-      @failover_strategy.define_singleton_method(:find_candidate) do |*args|
-        slaves.pop
-      end
       @nodes_discovered = true
     end
 
@@ -78,6 +74,10 @@ def force_syncing(node, serve_stale_reads)
       stop_processing
     end
 
+    def failover_strategy_candidate(snapshots)
+      @slaves.pop
+    end
+
     def delete_path(*args); end
     def create_path(*args); end
     def write_state(*args); end