SPEC-222: Delegate to topology from cluster

Author: durran

lib/mongo/cluster.rb

@@ -87,6 +87,34 @@ def add(host)
       end
     end
 
+    # Determine if the cluster would select a readable server for the
+    # provided read preference.
+    #
+    # @example Is a readable server present?
+    #   topology.has_readable_server?(server_selector)
+    #
+    # @param [ ServerSelector ] server_selector The server
+    #   selector.
+    #
+    # @return [ true, false ] If a readable server is present.
+    #
+    # @since 2.3.0
+    def has_readable_server?(server_selector)
+      topology.has_readable_server?(self, server_selector)
+    end
+
+    # Determine if the cluster would select a writable server.
+    #
+    # @example Is a writable server present?
+    #   topology.has_writable_server?
+    #
+    # @return [ true, false ] If a writable server is present.
+    #
+    # @since 2.3.0
+    def has_writable_server?
+      topology.has_writable_server?(self)
+    end
+
     # Instantiate the new cluster.
     #
     # @api private

lib/mongo/cluster/topology/replica_set.rb

@@ -90,7 +90,7 @@ def elect_primary(description, servers)
         #   topology.has_readable_server?(cluster, server_selector)
         #
         # @param [ Cluster ] cluster The cluster.
-        # @param [ ServerSelector, Symbol ] server_selector The server
+        # @param [ ServerSelector ] server_selector The server
         #   selector.
         #
         # @return [ true, false ] If a readable server is present.

lib/mongo/cluster/topology/sharded.rb

@@ -65,7 +65,7 @@ def elect_primary(description, servers); self; end
         #   topology.has_readable_server?(cluster, server_selector)
         #
         # @param [ Cluster ] cluster The cluster.
-        # @param [ ServerSelector, Symbol ] server_selector The server
+        # @param [ ServerSelector ] server_selector The server
         #   selector.
         #
         # @return [ true, false ] If a readable server is present.

lib/mongo/cluster/topology/single.rb

@@ -68,13 +68,15 @@ def elect_primary(description, servers); self; end
         #   topology.has_readable_server?(cluster, server_selector)
         #
         # @param [ Cluster ] cluster The cluster.
-        # @param [ ServerSelector, Symbol ] server_selector The server
+        # @param [ ServerSelector ] server_selector The server
         #   selector.
         #
         # @return [ true, false ] If a readable server is present.
         #
         # @since 2.3.0
-        def has_readable_server?(cluster, server_selector); true; end
+        def has_readable_server?(cluster, server_selector)
+          server_selector.candidates(cluster).any?
+        end
 
         # Determine if the topology would select a writable server for the
         # provided candidates.

lib/mongo/cluster/topology/unknown.rb

@@ -74,7 +74,7 @@ def elect_primary(description, servers)
         #   topology.has_readable_server?(cluster, server_selector)
         #
         # @param [ Cluster ] cluster The cluster.
-        # @param [ ServerSelector, Symbol ] server_selector The server
+        # @param [ ServerSelector ] server_selector The server
         #   selector.
         #
         # @return [ true, false ] If a readable server is present.

spec/mongo/cluster/topology/single_spec.rb

@@ -91,8 +91,56 @@
 
   describe '#has_readable_servers?' do
 
-    it 'returns true' do
-      expect(topology).to have_readable_server(nil, nil)
+    let(:cluster) do
+      double('cluster', servers: servers, single?: true)
+    end
+
+    let(:selector) do
+      Mongo::ServerSelector.get(mode: :primary)
+    end
+
+    context 'when using a direct connection to a primary' do
+
+      let(:servers) do
+        [ double('server', primary?: true) ]
+      end
+
+      it 'returns true' do
+        expect(topology).to have_readable_server(cluster, selector)
+      end
+    end
+
+    context 'when using a direct connection to a secondary' do
+
+      let(:servers) do
+        [ double('server', secondary?: true) ]
+      end
+
+      it 'returns true' do
+        expect(topology).to have_readable_server(cluster, selector)
+      end
+    end
+
+    context 'when using a direct connection to an arbiter' do
+
+      let(:servers) do
+        [ double('server', secondary?: true) ]
+      end
+
+      it 'returns true' do
+        expect(topology).to have_readable_server(cluster, selector)
+      end
+    end
+
+    context 'when no servers have been scanned' do
+
+      let(:servers) do
+        []
+      end
+
+      it 'returns false' do
+        expect(topology).to_not have_readable_server(cluster, selector)
+      end
     end
   end
 

spec/mongo/cluster_spec.rb

@@ -59,6 +59,24 @@
     end
   end
 
+  describe '#has_readable_server?' do
+
+    let(:selector) do
+      Mongo::ServerSelector.get(mode: :primary)
+    end
+
+    it 'delegates to the topology' do
+      expect(cluster).to have_readable_server(selector)
+    end
+  end
+
+  describe '#has_writable_server?' do
+
+    it 'delegates to the topology' do
+      expect(cluster).to_not have_writable_server
+    end
+  end
+
   describe '#inspect' do
 
     let(:preference) do